DATA COMMUNICATIONS Engr. Marlyn Quiambao-Camingal ECE Table of Contents Part One I. Introduction of Data Communications II. Data Transmission III. OSI IV.Networking (LAN) V.Internetworking (WAN) Part Two VI.Modem and Interface VII. ISDN VIII. X.25/Frame Relay/ATM IX.SONET/SDH X.TCP/IP
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A frame is an information unit whose source and destination are datalink layer entities A
frame is composed of the datalink layer header (and possibly a trailer) and upper-layer
data The header and the trailer contain control information intended for the data-link
layer entity in the destination system
A packet is an information unit whose source and destination are network-layer entities
A packet is composed of the network-layer header (and possibly a trailer0 and upper-layer data The header and the trailer contain control information intended for the
network-layer entity in the destination system The data from upper-layer entities is
encapsulated in the network-layer header and trailer
The term datagram usually refers to an information unit whose source and destination
are network-layer entities that use connectionless network services
The term segment usually refers to an information unit whose source and destination aretransport layer entities
A message is an information unit whose source and destination entities exist above the
network layer (often the application layer)
A cell is an information unit of a fixed size whose source and destination are datalink
layer entities Cells are used in switched environments such as ATM and SMDS A cell
is composed of the header and payload The header contains control informationintended for the destination datalink layer entity and is typically 5 bytes long The
payload contains upper-layer data that is encapsulated in the cell header and typically 48 bytes long
Data unit is a generic term that refers to a variety of information units Some commondata units are service data units (SDU) protocol data units (PDU) and bridge protocol
data units (BPDU) SDUs are information units from upper-layer protocols that define a
service request to a lower-layer protocol PDU is OSI terminology for a packet BPDUS
are used by the spanning-tree algorithm as hello messages
Three Basic elements in Layer Services
1 Service User is the OSI layer that requests services from an adjacent OSI layer
2 Service Provider is the OSI layer that provides services to service users
3 Service Access Point is a conceptual location at which one OSI layer can request the
Peer-to-peer ndash all nodes has equal authority in the networkClient-server ndash a certain node called server has full control over the network and
nodes in the network
LAN Components
1 Server
Is a computer in a network that shared by multiple users
2 Network Interface Card
A printed circuit board that plugs into a network server or client computer It
enables the computer to be physically connected to the network cable which provides the
physical layer connection among the computers in the network It performs electronicfunctions of the access method or datalink protocol
3 HubA device that acts as central connection of certain LAN topology It is capable of
regeneration and switching of signals from one node to another Also known as
concentrator multiple access unit transceiver or repeater
4 Cable
The transmission link in a network These are unshielded twisted pairs (UTP)
shielded twisted pair (STP) coaxial cable and fiber optics cable
5 Connector
The terminating end of the cable to be plug-in or connected to the device
6 Network Operating System (NOS)
The control program that resides in a server or workstation within a LAN Ithandles requests for data transfer from all the users of the networks It interact with the
application programs and the computerrsquos operating system
7 Client
It is the requesting computer from the supplying computers or server
8 Other Peripheral Devices
These are the devices attached to the network such as printers scanners and the
LAN Access Methodrarr it is unnecessary to have a MAC in pt-to-pt full duplex because there are
only two devices on the circuit and full duplex permits either device to
transmit at any time
rarr if it is point-to-point half duplex it needs MAC and also in multipoint full
duplex configurations since several devices share the same channelrarr to ensure that no two devices attempt to transmit data at the same time
1 Controlled Access
a X-on X-off
rarrthe oldest media access control protocols dating back to the days of theteletype
b Polling
rarr the process of sending signal to a terminal to transmit or asking it to receive
rarr it uses ldquoroll call pollingrdquo with scheme or sequence
Node 3its your time to transmitNode 1 its your turn to sendNode 4 you can transmit after node 1
c Token Passing
rarrA channel accessing arrangement that is best suited for ring topology witheither a baseband or broadband network It uses a token and the token circulate in
the network
Token is an electrical signal that circulate around the ring network from onestation to another If the station has the token it can send a message
2 Contention
rarr opposite of controlled access
rarr devices wait until the circuit is free and transmit whenever it has data to send
a Carrier Sense Multiple Access with Collision Detection (CSMACD)
rarrA channel accessing method a node monitors the line to determine if the line is
busy If the station has a message to transmit but the line is busy it waits for an
idle condition before it transmits its message
Collision is the situation when two nodes transmit simultaneously using one link
Backoff Time is the ceasing time before the station attempts to transmit again
Is the process where computers on a token-ring network detect a problem and
attempt to fix it
FDDI (Fiber Distributed Data Interface)
Uses fiber-optic cable and token-passing to create a very fast reliable networkoperating at speeds of 100 Mbps
It includes up to 500 nodes over a distance of 100 km It uses ring topology with two counter-rotating rings It is implement as true physical ring topology A break in a FDDI network results in packets being sent back on the second ring
1 End system (ES) is a network device that does not perform routing or other traffic
forwarding functions Typical ESs include such devices as terminals PCs and printers
2 Intermediate System (IS) is a network device that performs routing or other traffic-forwarding functions it includes devices such as routers switches and bridges
Intradomain IS communicates within a single autonomous system Interdomain IS communicates within and between autonomous systems
3 Area is a logical group of network segments and their attached devices Areas aresubdivisions of autonomous systems
4 Autonomous System (AS) is a collection of networks under a common administrationthat share a common routing strategy Autonomous system are subdivided into areas and
It involves three phases connection establishment- a single path between the
source and the destination systems is determined data transfer ndash transmitted sequentially
over the path that has been established and connection termination ndash termination of paththat has been establish
Connectionless
Offers two important advantages over connection-oriented service dynamic path
selection ndash enables traffic to be routed around network failures because paths are selectedon a packet-to-packet basis dynamic bandwidth allocation ndash used more efficiently
because network resources are not allocated a bandwidth that they will not use
Virtual Circuits
Switched Virtual CircuitA virtual circuit that is dynamically established on demand and terminated when
transmission is completed It has three phases circuit establishment data transfer and
circuit termination
Permanent Virtual Circuit
A permanently established virtual circuit consists of one mode the data transfer
Internetworking Devices
Hubs
bull A hub is a central network device that connects network devices in a startopology
bull Advanced hubs provide very high speed connectivity for FDDI Fast Ethernet
frame relay and ATM networks
bull It is also referred to as a concentrator (or switch) which is a device that can
have multiple inputs and outputs all active at a one time
bull Services offered by hubs
bull Provide a central unit from which to connect multiple nodes into one network
bull Permit large numbers of computers to be connected on single or multipleLANs
bull Reduce network congestion through centralizing network design
bull Provide multiprotocol services such as Ethernet-to-FDDI connectivity
bull Consolidate the network backbone
bull Enable high-speed communications
bull Provide connections for several different media types
bull Multiplexers are network devices that can receive multiple inputs and transmit
them to a shared network medium
bull A multiplexer is a switch that divides a communication medium into multiple
channels so several nodes can communicate at the same time
bull A signal that is multiplexed must be demultiplexed at the other endbull Multiplexers simply are switches used in old and new technology such as the
following
Telephone switching
Switching telecommunications lines to create multiple channels on a
single line Serial communications to enable more than one terminal to
communicate over a single line Fast Ethernet X25 ISDN frame relay ATM and other networking
technologies to create multiple communication channels over a single
communications cable
bull Work at the OSI physical level switching from channel to channel using one
of three physical methods
bull Time division multiplexing (TDM)
bull Frequency division multiplexing (FDM)
bull Wavelength division multiplexing (WDM)
Bridges
A bridge is a network device that connects different LAN segments using the same accessmethod
Bridges are used to
bull To extend a LAN when the maximum connections limit has been reached
bull To extend a LAN beyond the length limit
bull To segment LANs to reduce data traffic bottlenecks
bull To prevent unauthorized access to LAN (for security)
Standby indicator Pin 36 provides the confirmation signal from the DCE in response to
select standby (pin 32)
Send common Pin 37 provides a common signal return line for unbalanced circuits from
the DTE to the DCE
Electrical Specifications
bull EIA 449 uses two other standards to define its electrical specifications
RS-423 (for unbalanced circuits) and RS-422 (for balanced circuits)
RS-423 Unbalanced Mode
bull An unbalanced circuit specification meaning that it defines only one linefor propagating a signal All signals in this standard use a common return
(or ground) to complete the circuit
RS-422 Balanced Mode
bull A balanced circuit specification meaning that it defines two lines for the propagation of each signal Signals again use a common return (or ground)
for the return of the signal In balanced mode EIA-449 utilizes both pinsin each Category I but does not use the Category II pins The ratio of data
rate to distance is much higher that that of the unbalanced standard or of
EIA-232 10 Mbps for transmission of 40 feet bull In balanced mode two lines carry the same transmission it do not carry
identical signals The signal on one line is the complement of the signal
on the other When plotted the complement looks like a mirror image ofthe original signal Instead of listening to either actual signal the receiver
detects the differences between the two This mechanism makes a balanced circuit less susceptible to noise than an unbalanced circuit and
improves performance
EIA-530
bull A version of EIA-449 that uses DB-25 pins
bull The pin functions of EIA-530 are essentially the same of EIA-449
Category I plus three pins from Category II (the loopback circuits) Other pins in EIA-232 are omitted in EIA-530 such as ring indicator signal
quality detector and data signal rate selector
X21
bull Is an interface standard designed by ITU-T to address many problems
existing in the EIA interfaces and at the same time paves the way for alldigital communications
bull A large proportion of the circuits in the EIA interfaces are used forcontrol since these are necessary to implement control functions as
separate signals With a separate line control information is represented
only by positive and negative voltages But if control signals are encoded
using a meaningful control characters from a system such as ASCII it can be transmitted over data lines
bull X21 eliminates most of the control circuits of the EIA standards and
instead directs its traffic over the data circuits To make this consolidationof functionality possible both the DTE and the DCE must have added
circuit logic that enables them to transform the control codes into bit
streams that can be sent over the data line Both also need additional logicto discriminate between control information and data upon receipt
bull Design of X21 allows not only to use fewer pins but also to be used in
digital telecommunications where control information is sent from deviceto device over a network rather than just between a DTE and a DCE
bull X21 is useful both as an interface to connect digital computers to analogdevices such as modems and as a connector between digital computers and
digital interfaces such as ISDN and X25
Byte Timing
bull Another advantage offered by X21 is that of timing lines to control bytesynchronization in addition to the bit synchronization provided by the EIA
standards By adding a byte timing pulse improves the overall
synchronization of transmissions
Control and indication
bull Pins 3 and 5 of the DB-15 connector are used for the initial handshake or
agreement to begin transmitting Pin 3 is the equivalent of request to send
Pin 5 is the equivalent of clear to send
MODEMbull Modem stands for modulatordemodulator
bull A modulator converts a digital to an analog signalbull A demodulator converts an analog signal to a digital signal
bull The series of 1s and 0s are transformed through the mechanism of ASK
FSK PSK and QAM
Transmission Rate
Bandwidth
bull Every line has upper limit and a lower limit on the frequencies of the
signals it carry this limited range is called the bandwidth
It handles connection establishment and termination data transfer
and packet creation protocols Two types of PLP packets information and control
Up to 4096 channels may be multiplexed at the PLP level Specifies protocols to handle resizing of messages
FRAME RELAY LAYERSbull A technology that operates only at the physical and datalink layers No protocol is
specified for the physical layer the choice is up to the user
bull Eliminates the extensive error checking necessary in X25 protocol
bull It uses simplified version of HDLC protocol in the datalink layerbull It uses routing and switching functions of the datalink layers Frames not packets
are switched
bull It uses PVCs (permanent virtual circuits) Identified through a DLCI (dalta linkconnection identifier)
bull A switch in frame relay performs error checking and routing Error correction is
left to the other protocols at the higher layers
bull Flow control is handled through setting the BECN (backwards explicit congestionnotification) and FECN (forward explicit congestion notification) in the address
field of the frame
bull
ASYNCHRONOUS TRANSFER MODE (ATM)
bull Is the cell relay protocol designed by the ATM forum and adopted by theITU-T
bull In ATM some software functions have moved to hardware this can
increase the data rate
Terms
Cell is the data packet is called a and is composed of 53 bytes (5 bytes of header and 48 bytes of payload) Because each cell is the same size and all are relatively small delay
and other problems associated with multiplexing different sized packets are avoided
A cell network is based on permanent virtual circuit (PVC) routing
bull Virtual Path Identifier (VPI) specifies the path a cell should take
1 Virtual path (VP) switching ndash channels within each VP remain with the VP
2 Virtual path and channel (VPC) switching ndash a channel from one VP may pass into
another VP
IXSDHSONET
Synchronous Optical Network (SONET)
Developed by ANSI
Synchronous Digital Hierarchy (SDH)
Developed by ITU-T
SONETSDH
The two are nearly identical ANSI and ITU-T defined standards that arefundamentally similar and ultimately compatible
Is a synchronous network a single clock is used to handle the timing of
transmissions and equipment across the entire network
SONET
It defines the hierarchy of signals called synchronous transport signals (STS)
Optical carrier (OC) levels are the implementation of STS
SONETSDH Rates
STS OC Rate (Mbps) STM
STS-1 OC-1 5184
STS-3 OC-3 15552 STM-1
STS-9 OC-9 46656 STM-3
STS-12 OC-12 62208 STM-4
STS-18 OC-18 93312 STM-6
STS-24 OC-24 124416 STM-8
STS-36 OC-36 186623 STM-12
STS-48 OC-48 248832 STM-16
STS-96 OC-96 497664 STM-32
STS-192 OC-192 995328 STM-64
STM-synchronous transport module
SONET Four Layers
1 Photonic layer is the lowest and performs physical layer activities
A frame at the photonic layer for STS-1 consists of 6480 bits (8000 framessec)
2-4 Section Line and Path layers correspond to the OSI modelrsquos datalink layer Eachof these layers is responsible for signal transfer across a specific portion of the
1 STS multiplexer combines several optical signals to make an STS signal2 Regenerator removes noise from optical signal
3 Adddrop multiplexer adds STS signals from different paths and removes STS signal
from a path
XTCPIP
Transmission Control ProtocolInternetworking Protocol (TCPIP)
Is a set of rules and procedures that governs the exchange of messages in an
internetwork Originally developed as a protocol for networks that wanted to be connected to
ARPANET a US Department of Defense project now known as Internet
Is a five-layer protocol suite whose bottom four layers match the OSI model fairly
closely The highest level the application layer corresponds to OSIrsquos top threelayers
Internet Protocol (IP) Is defined at the network layer
Unreliable and connectionless Is basically the set of rules for one network communicating with any other To be part of internet organization needs an internet network number unique
number to be included in any packet sent out of the network onto the internet
IP packet is known as datagram consists of a variable header and a variable data
field
IP Address
Uniquely defines the connection of a host to its network The host with more than
one IP address is multi-homed host
IP Addressing
32 bit binary number usually represented as 4 decimal values Equivalent to 4 octets ( 8 bits each decimal value ) Dotted decimal notation Consists of 2 parts the network and the node
Network ndash identifier of particular network on the internet
Host ndash identifier of a particular device which can be a server or a
A frame is an information unit whose source and destination are datalink layer entities A
frame is composed of the datalink layer header (and possibly a trailer) and upper-layer
data The header and the trailer contain control information intended for the data-link
layer entity in the destination system
A packet is an information unit whose source and destination are network-layer entities
A packet is composed of the network-layer header (and possibly a trailer0 and upper-layer data The header and the trailer contain control information intended for the
network-layer entity in the destination system The data from upper-layer entities is
encapsulated in the network-layer header and trailer
The term datagram usually refers to an information unit whose source and destination
are network-layer entities that use connectionless network services
The term segment usually refers to an information unit whose source and destination aretransport layer entities
A message is an information unit whose source and destination entities exist above the
network layer (often the application layer)
A cell is an information unit of a fixed size whose source and destination are datalink
layer entities Cells are used in switched environments such as ATM and SMDS A cell
is composed of the header and payload The header contains control informationintended for the destination datalink layer entity and is typically 5 bytes long The
payload contains upper-layer data that is encapsulated in the cell header and typically 48 bytes long
Data unit is a generic term that refers to a variety of information units Some commondata units are service data units (SDU) protocol data units (PDU) and bridge protocol
data units (BPDU) SDUs are information units from upper-layer protocols that define a
service request to a lower-layer protocol PDU is OSI terminology for a packet BPDUS
are used by the spanning-tree algorithm as hello messages
Three Basic elements in Layer Services
1 Service User is the OSI layer that requests services from an adjacent OSI layer
2 Service Provider is the OSI layer that provides services to service users
3 Service Access Point is a conceptual location at which one OSI layer can request the
Peer-to-peer ndash all nodes has equal authority in the networkClient-server ndash a certain node called server has full control over the network and
nodes in the network
LAN Components
1 Server
Is a computer in a network that shared by multiple users
2 Network Interface Card
A printed circuit board that plugs into a network server or client computer It
enables the computer to be physically connected to the network cable which provides the
physical layer connection among the computers in the network It performs electronicfunctions of the access method or datalink protocol
3 HubA device that acts as central connection of certain LAN topology It is capable of
regeneration and switching of signals from one node to another Also known as
concentrator multiple access unit transceiver or repeater
4 Cable
The transmission link in a network These are unshielded twisted pairs (UTP)
shielded twisted pair (STP) coaxial cable and fiber optics cable
5 Connector
The terminating end of the cable to be plug-in or connected to the device
6 Network Operating System (NOS)
The control program that resides in a server or workstation within a LAN Ithandles requests for data transfer from all the users of the networks It interact with the
application programs and the computerrsquos operating system
7 Client
It is the requesting computer from the supplying computers or server
8 Other Peripheral Devices
These are the devices attached to the network such as printers scanners and the
LAN Access Methodrarr it is unnecessary to have a MAC in pt-to-pt full duplex because there are
only two devices on the circuit and full duplex permits either device to
transmit at any time
rarr if it is point-to-point half duplex it needs MAC and also in multipoint full
duplex configurations since several devices share the same channelrarr to ensure that no two devices attempt to transmit data at the same time
1 Controlled Access
a X-on X-off
rarrthe oldest media access control protocols dating back to the days of theteletype
b Polling
rarr the process of sending signal to a terminal to transmit or asking it to receive
rarr it uses ldquoroll call pollingrdquo with scheme or sequence
Node 3its your time to transmitNode 1 its your turn to sendNode 4 you can transmit after node 1
c Token Passing
rarrA channel accessing arrangement that is best suited for ring topology witheither a baseband or broadband network It uses a token and the token circulate in
the network
Token is an electrical signal that circulate around the ring network from onestation to another If the station has the token it can send a message
2 Contention
rarr opposite of controlled access
rarr devices wait until the circuit is free and transmit whenever it has data to send
a Carrier Sense Multiple Access with Collision Detection (CSMACD)
rarrA channel accessing method a node monitors the line to determine if the line is
busy If the station has a message to transmit but the line is busy it waits for an
idle condition before it transmits its message
Collision is the situation when two nodes transmit simultaneously using one link
Backoff Time is the ceasing time before the station attempts to transmit again
Is the process where computers on a token-ring network detect a problem and
attempt to fix it
FDDI (Fiber Distributed Data Interface)
Uses fiber-optic cable and token-passing to create a very fast reliable networkoperating at speeds of 100 Mbps
It includes up to 500 nodes over a distance of 100 km It uses ring topology with two counter-rotating rings It is implement as true physical ring topology A break in a FDDI network results in packets being sent back on the second ring
1 End system (ES) is a network device that does not perform routing or other traffic
forwarding functions Typical ESs include such devices as terminals PCs and printers
2 Intermediate System (IS) is a network device that performs routing or other traffic-forwarding functions it includes devices such as routers switches and bridges
Intradomain IS communicates within a single autonomous system Interdomain IS communicates within and between autonomous systems
3 Area is a logical group of network segments and their attached devices Areas aresubdivisions of autonomous systems
4 Autonomous System (AS) is a collection of networks under a common administrationthat share a common routing strategy Autonomous system are subdivided into areas and
It involves three phases connection establishment- a single path between the
source and the destination systems is determined data transfer ndash transmitted sequentially
over the path that has been established and connection termination ndash termination of paththat has been establish
Connectionless
Offers two important advantages over connection-oriented service dynamic path
selection ndash enables traffic to be routed around network failures because paths are selectedon a packet-to-packet basis dynamic bandwidth allocation ndash used more efficiently
because network resources are not allocated a bandwidth that they will not use
Virtual Circuits
Switched Virtual CircuitA virtual circuit that is dynamically established on demand and terminated when
transmission is completed It has three phases circuit establishment data transfer and
circuit termination
Permanent Virtual Circuit
A permanently established virtual circuit consists of one mode the data transfer
Internetworking Devices
Hubs
bull A hub is a central network device that connects network devices in a startopology
bull Advanced hubs provide very high speed connectivity for FDDI Fast Ethernet
frame relay and ATM networks
bull It is also referred to as a concentrator (or switch) which is a device that can
have multiple inputs and outputs all active at a one time
bull Services offered by hubs
bull Provide a central unit from which to connect multiple nodes into one network
bull Permit large numbers of computers to be connected on single or multipleLANs
bull Reduce network congestion through centralizing network design
bull Provide multiprotocol services such as Ethernet-to-FDDI connectivity
bull Consolidate the network backbone
bull Enable high-speed communications
bull Provide connections for several different media types
bull Multiplexers are network devices that can receive multiple inputs and transmit
them to a shared network medium
bull A multiplexer is a switch that divides a communication medium into multiple
channels so several nodes can communicate at the same time
bull A signal that is multiplexed must be demultiplexed at the other endbull Multiplexers simply are switches used in old and new technology such as the
following
Telephone switching
Switching telecommunications lines to create multiple channels on a
single line Serial communications to enable more than one terminal to
communicate over a single line Fast Ethernet X25 ISDN frame relay ATM and other networking
technologies to create multiple communication channels over a single
communications cable
bull Work at the OSI physical level switching from channel to channel using one
of three physical methods
bull Time division multiplexing (TDM)
bull Frequency division multiplexing (FDM)
bull Wavelength division multiplexing (WDM)
Bridges
A bridge is a network device that connects different LAN segments using the same accessmethod
Bridges are used to
bull To extend a LAN when the maximum connections limit has been reached
bull To extend a LAN beyond the length limit
bull To segment LANs to reduce data traffic bottlenecks
bull To prevent unauthorized access to LAN (for security)
Standby indicator Pin 36 provides the confirmation signal from the DCE in response to
select standby (pin 32)
Send common Pin 37 provides a common signal return line for unbalanced circuits from
the DTE to the DCE
Electrical Specifications
bull EIA 449 uses two other standards to define its electrical specifications
RS-423 (for unbalanced circuits) and RS-422 (for balanced circuits)
RS-423 Unbalanced Mode
bull An unbalanced circuit specification meaning that it defines only one linefor propagating a signal All signals in this standard use a common return
(or ground) to complete the circuit
RS-422 Balanced Mode
bull A balanced circuit specification meaning that it defines two lines for the propagation of each signal Signals again use a common return (or ground)
for the return of the signal In balanced mode EIA-449 utilizes both pinsin each Category I but does not use the Category II pins The ratio of data
rate to distance is much higher that that of the unbalanced standard or of
EIA-232 10 Mbps for transmission of 40 feet bull In balanced mode two lines carry the same transmission it do not carry
identical signals The signal on one line is the complement of the signal
on the other When plotted the complement looks like a mirror image ofthe original signal Instead of listening to either actual signal the receiver
detects the differences between the two This mechanism makes a balanced circuit less susceptible to noise than an unbalanced circuit and
improves performance
EIA-530
bull A version of EIA-449 that uses DB-25 pins
bull The pin functions of EIA-530 are essentially the same of EIA-449
Category I plus three pins from Category II (the loopback circuits) Other pins in EIA-232 are omitted in EIA-530 such as ring indicator signal
quality detector and data signal rate selector
X21
bull Is an interface standard designed by ITU-T to address many problems
existing in the EIA interfaces and at the same time paves the way for alldigital communications
bull A large proportion of the circuits in the EIA interfaces are used forcontrol since these are necessary to implement control functions as
separate signals With a separate line control information is represented
only by positive and negative voltages But if control signals are encoded
using a meaningful control characters from a system such as ASCII it can be transmitted over data lines
bull X21 eliminates most of the control circuits of the EIA standards and
instead directs its traffic over the data circuits To make this consolidationof functionality possible both the DTE and the DCE must have added
circuit logic that enables them to transform the control codes into bit
streams that can be sent over the data line Both also need additional logicto discriminate between control information and data upon receipt
bull Design of X21 allows not only to use fewer pins but also to be used in
digital telecommunications where control information is sent from deviceto device over a network rather than just between a DTE and a DCE
bull X21 is useful both as an interface to connect digital computers to analogdevices such as modems and as a connector between digital computers and
digital interfaces such as ISDN and X25
Byte Timing
bull Another advantage offered by X21 is that of timing lines to control bytesynchronization in addition to the bit synchronization provided by the EIA
standards By adding a byte timing pulse improves the overall
synchronization of transmissions
Control and indication
bull Pins 3 and 5 of the DB-15 connector are used for the initial handshake or
agreement to begin transmitting Pin 3 is the equivalent of request to send
Pin 5 is the equivalent of clear to send
MODEMbull Modem stands for modulatordemodulator
bull A modulator converts a digital to an analog signalbull A demodulator converts an analog signal to a digital signal
bull The series of 1s and 0s are transformed through the mechanism of ASK
FSK PSK and QAM
Transmission Rate
Bandwidth
bull Every line has upper limit and a lower limit on the frequencies of the
signals it carry this limited range is called the bandwidth
It handles connection establishment and termination data transfer
and packet creation protocols Two types of PLP packets information and control
Up to 4096 channels may be multiplexed at the PLP level Specifies protocols to handle resizing of messages
FRAME RELAY LAYERSbull A technology that operates only at the physical and datalink layers No protocol is
specified for the physical layer the choice is up to the user
bull Eliminates the extensive error checking necessary in X25 protocol
bull It uses simplified version of HDLC protocol in the datalink layerbull It uses routing and switching functions of the datalink layers Frames not packets
are switched
bull It uses PVCs (permanent virtual circuits) Identified through a DLCI (dalta linkconnection identifier)
bull A switch in frame relay performs error checking and routing Error correction is
left to the other protocols at the higher layers
bull Flow control is handled through setting the BECN (backwards explicit congestionnotification) and FECN (forward explicit congestion notification) in the address
field of the frame
bull
ASYNCHRONOUS TRANSFER MODE (ATM)
bull Is the cell relay protocol designed by the ATM forum and adopted by theITU-T
bull In ATM some software functions have moved to hardware this can
increase the data rate
Terms
Cell is the data packet is called a and is composed of 53 bytes (5 bytes of header and 48 bytes of payload) Because each cell is the same size and all are relatively small delay
and other problems associated with multiplexing different sized packets are avoided
A cell network is based on permanent virtual circuit (PVC) routing
bull Virtual Path Identifier (VPI) specifies the path a cell should take
1 Virtual path (VP) switching ndash channels within each VP remain with the VP
2 Virtual path and channel (VPC) switching ndash a channel from one VP may pass into
another VP
IXSDHSONET
Synchronous Optical Network (SONET)
Developed by ANSI
Synchronous Digital Hierarchy (SDH)
Developed by ITU-T
SONETSDH
The two are nearly identical ANSI and ITU-T defined standards that arefundamentally similar and ultimately compatible
Is a synchronous network a single clock is used to handle the timing of
transmissions and equipment across the entire network
SONET
It defines the hierarchy of signals called synchronous transport signals (STS)
Optical carrier (OC) levels are the implementation of STS
SONETSDH Rates
STS OC Rate (Mbps) STM
STS-1 OC-1 5184
STS-3 OC-3 15552 STM-1
STS-9 OC-9 46656 STM-3
STS-12 OC-12 62208 STM-4
STS-18 OC-18 93312 STM-6
STS-24 OC-24 124416 STM-8
STS-36 OC-36 186623 STM-12
STS-48 OC-48 248832 STM-16
STS-96 OC-96 497664 STM-32
STS-192 OC-192 995328 STM-64
STM-synchronous transport module
SONET Four Layers
1 Photonic layer is the lowest and performs physical layer activities
A frame at the photonic layer for STS-1 consists of 6480 bits (8000 framessec)
2-4 Section Line and Path layers correspond to the OSI modelrsquos datalink layer Eachof these layers is responsible for signal transfer across a specific portion of the
1 STS multiplexer combines several optical signals to make an STS signal2 Regenerator removes noise from optical signal
3 Adddrop multiplexer adds STS signals from different paths and removes STS signal
from a path
XTCPIP
Transmission Control ProtocolInternetworking Protocol (TCPIP)
Is a set of rules and procedures that governs the exchange of messages in an
internetwork Originally developed as a protocol for networks that wanted to be connected to
ARPANET a US Department of Defense project now known as Internet
Is a five-layer protocol suite whose bottom four layers match the OSI model fairly
closely The highest level the application layer corresponds to OSIrsquos top threelayers
Internet Protocol (IP) Is defined at the network layer
Unreliable and connectionless Is basically the set of rules for one network communicating with any other To be part of internet organization needs an internet network number unique
number to be included in any packet sent out of the network onto the internet
IP packet is known as datagram consists of a variable header and a variable data
field
IP Address
Uniquely defines the connection of a host to its network The host with more than
one IP address is multi-homed host
IP Addressing
32 bit binary number usually represented as 4 decimal values Equivalent to 4 octets ( 8 bits each decimal value ) Dotted decimal notation Consists of 2 parts the network and the node
Network ndash identifier of particular network on the internet
Host ndash identifier of a particular device which can be a server or a
A frame is an information unit whose source and destination are datalink layer entities A
frame is composed of the datalink layer header (and possibly a trailer) and upper-layer
data The header and the trailer contain control information intended for the data-link
layer entity in the destination system
A packet is an information unit whose source and destination are network-layer entities
A packet is composed of the network-layer header (and possibly a trailer0 and upper-layer data The header and the trailer contain control information intended for the
network-layer entity in the destination system The data from upper-layer entities is
encapsulated in the network-layer header and trailer
The term datagram usually refers to an information unit whose source and destination
are network-layer entities that use connectionless network services
The term segment usually refers to an information unit whose source and destination aretransport layer entities
A message is an information unit whose source and destination entities exist above the
network layer (often the application layer)
A cell is an information unit of a fixed size whose source and destination are datalink
layer entities Cells are used in switched environments such as ATM and SMDS A cell
is composed of the header and payload The header contains control informationintended for the destination datalink layer entity and is typically 5 bytes long The
payload contains upper-layer data that is encapsulated in the cell header and typically 48 bytes long
Data unit is a generic term that refers to a variety of information units Some commondata units are service data units (SDU) protocol data units (PDU) and bridge protocol
data units (BPDU) SDUs are information units from upper-layer protocols that define a
service request to a lower-layer protocol PDU is OSI terminology for a packet BPDUS
are used by the spanning-tree algorithm as hello messages
Three Basic elements in Layer Services
1 Service User is the OSI layer that requests services from an adjacent OSI layer
2 Service Provider is the OSI layer that provides services to service users
3 Service Access Point is a conceptual location at which one OSI layer can request the
Peer-to-peer ndash all nodes has equal authority in the networkClient-server ndash a certain node called server has full control over the network and
nodes in the network
LAN Components
1 Server
Is a computer in a network that shared by multiple users
2 Network Interface Card
A printed circuit board that plugs into a network server or client computer It
enables the computer to be physically connected to the network cable which provides the
physical layer connection among the computers in the network It performs electronicfunctions of the access method or datalink protocol
3 HubA device that acts as central connection of certain LAN topology It is capable of
regeneration and switching of signals from one node to another Also known as
concentrator multiple access unit transceiver or repeater
4 Cable
The transmission link in a network These are unshielded twisted pairs (UTP)
shielded twisted pair (STP) coaxial cable and fiber optics cable
5 Connector
The terminating end of the cable to be plug-in or connected to the device
6 Network Operating System (NOS)
The control program that resides in a server or workstation within a LAN Ithandles requests for data transfer from all the users of the networks It interact with the
application programs and the computerrsquos operating system
7 Client
It is the requesting computer from the supplying computers or server
8 Other Peripheral Devices
These are the devices attached to the network such as printers scanners and the
LAN Access Methodrarr it is unnecessary to have a MAC in pt-to-pt full duplex because there are
only two devices on the circuit and full duplex permits either device to
transmit at any time
rarr if it is point-to-point half duplex it needs MAC and also in multipoint full
duplex configurations since several devices share the same channelrarr to ensure that no two devices attempt to transmit data at the same time
1 Controlled Access
a X-on X-off
rarrthe oldest media access control protocols dating back to the days of theteletype
b Polling
rarr the process of sending signal to a terminal to transmit or asking it to receive
rarr it uses ldquoroll call pollingrdquo with scheme or sequence
Node 3its your time to transmitNode 1 its your turn to sendNode 4 you can transmit after node 1
c Token Passing
rarrA channel accessing arrangement that is best suited for ring topology witheither a baseband or broadband network It uses a token and the token circulate in
the network
Token is an electrical signal that circulate around the ring network from onestation to another If the station has the token it can send a message
2 Contention
rarr opposite of controlled access
rarr devices wait until the circuit is free and transmit whenever it has data to send
a Carrier Sense Multiple Access with Collision Detection (CSMACD)
rarrA channel accessing method a node monitors the line to determine if the line is
busy If the station has a message to transmit but the line is busy it waits for an
idle condition before it transmits its message
Collision is the situation when two nodes transmit simultaneously using one link
Backoff Time is the ceasing time before the station attempts to transmit again
Is the process where computers on a token-ring network detect a problem and
attempt to fix it
FDDI (Fiber Distributed Data Interface)
Uses fiber-optic cable and token-passing to create a very fast reliable networkoperating at speeds of 100 Mbps
It includes up to 500 nodes over a distance of 100 km It uses ring topology with two counter-rotating rings It is implement as true physical ring topology A break in a FDDI network results in packets being sent back on the second ring
1 End system (ES) is a network device that does not perform routing or other traffic
forwarding functions Typical ESs include such devices as terminals PCs and printers
2 Intermediate System (IS) is a network device that performs routing or other traffic-forwarding functions it includes devices such as routers switches and bridges
Intradomain IS communicates within a single autonomous system Interdomain IS communicates within and between autonomous systems
3 Area is a logical group of network segments and their attached devices Areas aresubdivisions of autonomous systems
4 Autonomous System (AS) is a collection of networks under a common administrationthat share a common routing strategy Autonomous system are subdivided into areas and
It involves three phases connection establishment- a single path between the
source and the destination systems is determined data transfer ndash transmitted sequentially
over the path that has been established and connection termination ndash termination of paththat has been establish
Connectionless
Offers two important advantages over connection-oriented service dynamic path
selection ndash enables traffic to be routed around network failures because paths are selectedon a packet-to-packet basis dynamic bandwidth allocation ndash used more efficiently
because network resources are not allocated a bandwidth that they will not use
Virtual Circuits
Switched Virtual CircuitA virtual circuit that is dynamically established on demand and terminated when
transmission is completed It has three phases circuit establishment data transfer and
circuit termination
Permanent Virtual Circuit
A permanently established virtual circuit consists of one mode the data transfer
Internetworking Devices
Hubs
bull A hub is a central network device that connects network devices in a startopology
bull Advanced hubs provide very high speed connectivity for FDDI Fast Ethernet
frame relay and ATM networks
bull It is also referred to as a concentrator (or switch) which is a device that can
have multiple inputs and outputs all active at a one time
bull Services offered by hubs
bull Provide a central unit from which to connect multiple nodes into one network
bull Permit large numbers of computers to be connected on single or multipleLANs
bull Reduce network congestion through centralizing network design
bull Provide multiprotocol services such as Ethernet-to-FDDI connectivity
bull Consolidate the network backbone
bull Enable high-speed communications
bull Provide connections for several different media types
bull Multiplexers are network devices that can receive multiple inputs and transmit
them to a shared network medium
bull A multiplexer is a switch that divides a communication medium into multiple
channels so several nodes can communicate at the same time
bull A signal that is multiplexed must be demultiplexed at the other endbull Multiplexers simply are switches used in old and new technology such as the
following
Telephone switching
Switching telecommunications lines to create multiple channels on a
single line Serial communications to enable more than one terminal to
communicate over a single line Fast Ethernet X25 ISDN frame relay ATM and other networking
technologies to create multiple communication channels over a single
communications cable
bull Work at the OSI physical level switching from channel to channel using one
of three physical methods
bull Time division multiplexing (TDM)
bull Frequency division multiplexing (FDM)
bull Wavelength division multiplexing (WDM)
Bridges
A bridge is a network device that connects different LAN segments using the same accessmethod
Bridges are used to
bull To extend a LAN when the maximum connections limit has been reached
bull To extend a LAN beyond the length limit
bull To segment LANs to reduce data traffic bottlenecks
bull To prevent unauthorized access to LAN (for security)
Standby indicator Pin 36 provides the confirmation signal from the DCE in response to
select standby (pin 32)
Send common Pin 37 provides a common signal return line for unbalanced circuits from
the DTE to the DCE
Electrical Specifications
bull EIA 449 uses two other standards to define its electrical specifications
RS-423 (for unbalanced circuits) and RS-422 (for balanced circuits)
RS-423 Unbalanced Mode
bull An unbalanced circuit specification meaning that it defines only one linefor propagating a signal All signals in this standard use a common return
(or ground) to complete the circuit
RS-422 Balanced Mode
bull A balanced circuit specification meaning that it defines two lines for the propagation of each signal Signals again use a common return (or ground)
for the return of the signal In balanced mode EIA-449 utilizes both pinsin each Category I but does not use the Category II pins The ratio of data
rate to distance is much higher that that of the unbalanced standard or of
EIA-232 10 Mbps for transmission of 40 feet bull In balanced mode two lines carry the same transmission it do not carry
identical signals The signal on one line is the complement of the signal
on the other When plotted the complement looks like a mirror image ofthe original signal Instead of listening to either actual signal the receiver
detects the differences between the two This mechanism makes a balanced circuit less susceptible to noise than an unbalanced circuit and
improves performance
EIA-530
bull A version of EIA-449 that uses DB-25 pins
bull The pin functions of EIA-530 are essentially the same of EIA-449
Category I plus three pins from Category II (the loopback circuits) Other pins in EIA-232 are omitted in EIA-530 such as ring indicator signal
quality detector and data signal rate selector
X21
bull Is an interface standard designed by ITU-T to address many problems
existing in the EIA interfaces and at the same time paves the way for alldigital communications
bull A large proportion of the circuits in the EIA interfaces are used forcontrol since these are necessary to implement control functions as
separate signals With a separate line control information is represented
only by positive and negative voltages But if control signals are encoded
using a meaningful control characters from a system such as ASCII it can be transmitted over data lines
bull X21 eliminates most of the control circuits of the EIA standards and
instead directs its traffic over the data circuits To make this consolidationof functionality possible both the DTE and the DCE must have added
circuit logic that enables them to transform the control codes into bit
streams that can be sent over the data line Both also need additional logicto discriminate between control information and data upon receipt
bull Design of X21 allows not only to use fewer pins but also to be used in
digital telecommunications where control information is sent from deviceto device over a network rather than just between a DTE and a DCE
bull X21 is useful both as an interface to connect digital computers to analogdevices such as modems and as a connector between digital computers and
digital interfaces such as ISDN and X25
Byte Timing
bull Another advantage offered by X21 is that of timing lines to control bytesynchronization in addition to the bit synchronization provided by the EIA
standards By adding a byte timing pulse improves the overall
synchronization of transmissions
Control and indication
bull Pins 3 and 5 of the DB-15 connector are used for the initial handshake or
agreement to begin transmitting Pin 3 is the equivalent of request to send
Pin 5 is the equivalent of clear to send
MODEMbull Modem stands for modulatordemodulator
bull A modulator converts a digital to an analog signalbull A demodulator converts an analog signal to a digital signal
bull The series of 1s and 0s are transformed through the mechanism of ASK
FSK PSK and QAM
Transmission Rate
Bandwidth
bull Every line has upper limit and a lower limit on the frequencies of the
signals it carry this limited range is called the bandwidth
It handles connection establishment and termination data transfer
and packet creation protocols Two types of PLP packets information and control
Up to 4096 channels may be multiplexed at the PLP level Specifies protocols to handle resizing of messages
FRAME RELAY LAYERSbull A technology that operates only at the physical and datalink layers No protocol is
specified for the physical layer the choice is up to the user
bull Eliminates the extensive error checking necessary in X25 protocol
bull It uses simplified version of HDLC protocol in the datalink layerbull It uses routing and switching functions of the datalink layers Frames not packets
are switched
bull It uses PVCs (permanent virtual circuits) Identified through a DLCI (dalta linkconnection identifier)
bull A switch in frame relay performs error checking and routing Error correction is
left to the other protocols at the higher layers
bull Flow control is handled through setting the BECN (backwards explicit congestionnotification) and FECN (forward explicit congestion notification) in the address
field of the frame
bull
ASYNCHRONOUS TRANSFER MODE (ATM)
bull Is the cell relay protocol designed by the ATM forum and adopted by theITU-T
bull In ATM some software functions have moved to hardware this can
increase the data rate
Terms
Cell is the data packet is called a and is composed of 53 bytes (5 bytes of header and 48 bytes of payload) Because each cell is the same size and all are relatively small delay
and other problems associated with multiplexing different sized packets are avoided
A cell network is based on permanent virtual circuit (PVC) routing
bull Virtual Path Identifier (VPI) specifies the path a cell should take
1 Virtual path (VP) switching ndash channels within each VP remain with the VP
2 Virtual path and channel (VPC) switching ndash a channel from one VP may pass into
another VP
IXSDHSONET
Synchronous Optical Network (SONET)
Developed by ANSI
Synchronous Digital Hierarchy (SDH)
Developed by ITU-T
SONETSDH
The two are nearly identical ANSI and ITU-T defined standards that arefundamentally similar and ultimately compatible
Is a synchronous network a single clock is used to handle the timing of
transmissions and equipment across the entire network
SONET
It defines the hierarchy of signals called synchronous transport signals (STS)
Optical carrier (OC) levels are the implementation of STS
SONETSDH Rates
STS OC Rate (Mbps) STM
STS-1 OC-1 5184
STS-3 OC-3 15552 STM-1
STS-9 OC-9 46656 STM-3
STS-12 OC-12 62208 STM-4
STS-18 OC-18 93312 STM-6
STS-24 OC-24 124416 STM-8
STS-36 OC-36 186623 STM-12
STS-48 OC-48 248832 STM-16
STS-96 OC-96 497664 STM-32
STS-192 OC-192 995328 STM-64
STM-synchronous transport module
SONET Four Layers
1 Photonic layer is the lowest and performs physical layer activities
A frame at the photonic layer for STS-1 consists of 6480 bits (8000 framessec)
2-4 Section Line and Path layers correspond to the OSI modelrsquos datalink layer Eachof these layers is responsible for signal transfer across a specific portion of the
1 STS multiplexer combines several optical signals to make an STS signal2 Regenerator removes noise from optical signal
3 Adddrop multiplexer adds STS signals from different paths and removes STS signal
from a path
XTCPIP
Transmission Control ProtocolInternetworking Protocol (TCPIP)
Is a set of rules and procedures that governs the exchange of messages in an
internetwork Originally developed as a protocol for networks that wanted to be connected to
ARPANET a US Department of Defense project now known as Internet
Is a five-layer protocol suite whose bottom four layers match the OSI model fairly
closely The highest level the application layer corresponds to OSIrsquos top threelayers
Internet Protocol (IP) Is defined at the network layer
Unreliable and connectionless Is basically the set of rules for one network communicating with any other To be part of internet organization needs an internet network number unique
number to be included in any packet sent out of the network onto the internet
IP packet is known as datagram consists of a variable header and a variable data
field
IP Address
Uniquely defines the connection of a host to its network The host with more than
one IP address is multi-homed host
IP Addressing
32 bit binary number usually represented as 4 decimal values Equivalent to 4 octets ( 8 bits each decimal value ) Dotted decimal notation Consists of 2 parts the network and the node
Network ndash identifier of particular network on the internet
Host ndash identifier of a particular device which can be a server or a
A frame is an information unit whose source and destination are datalink layer entities A
frame is composed of the datalink layer header (and possibly a trailer) and upper-layer
data The header and the trailer contain control information intended for the data-link
layer entity in the destination system
A packet is an information unit whose source and destination are network-layer entities
A packet is composed of the network-layer header (and possibly a trailer0 and upper-layer data The header and the trailer contain control information intended for the
network-layer entity in the destination system The data from upper-layer entities is
encapsulated in the network-layer header and trailer
The term datagram usually refers to an information unit whose source and destination
are network-layer entities that use connectionless network services
The term segment usually refers to an information unit whose source and destination aretransport layer entities
A message is an information unit whose source and destination entities exist above the
network layer (often the application layer)
A cell is an information unit of a fixed size whose source and destination are datalink
layer entities Cells are used in switched environments such as ATM and SMDS A cell
is composed of the header and payload The header contains control informationintended for the destination datalink layer entity and is typically 5 bytes long The
payload contains upper-layer data that is encapsulated in the cell header and typically 48 bytes long
Data unit is a generic term that refers to a variety of information units Some commondata units are service data units (SDU) protocol data units (PDU) and bridge protocol
data units (BPDU) SDUs are information units from upper-layer protocols that define a
service request to a lower-layer protocol PDU is OSI terminology for a packet BPDUS
are used by the spanning-tree algorithm as hello messages
Three Basic elements in Layer Services
1 Service User is the OSI layer that requests services from an adjacent OSI layer
2 Service Provider is the OSI layer that provides services to service users
3 Service Access Point is a conceptual location at which one OSI layer can request the
Peer-to-peer ndash all nodes has equal authority in the networkClient-server ndash a certain node called server has full control over the network and
nodes in the network
LAN Components
1 Server
Is a computer in a network that shared by multiple users
2 Network Interface Card
A printed circuit board that plugs into a network server or client computer It
enables the computer to be physically connected to the network cable which provides the
physical layer connection among the computers in the network It performs electronicfunctions of the access method or datalink protocol
3 HubA device that acts as central connection of certain LAN topology It is capable of
regeneration and switching of signals from one node to another Also known as
concentrator multiple access unit transceiver or repeater
4 Cable
The transmission link in a network These are unshielded twisted pairs (UTP)
shielded twisted pair (STP) coaxial cable and fiber optics cable
5 Connector
The terminating end of the cable to be plug-in or connected to the device
6 Network Operating System (NOS)
The control program that resides in a server or workstation within a LAN Ithandles requests for data transfer from all the users of the networks It interact with the
application programs and the computerrsquos operating system
7 Client
It is the requesting computer from the supplying computers or server
8 Other Peripheral Devices
These are the devices attached to the network such as printers scanners and the
LAN Access Methodrarr it is unnecessary to have a MAC in pt-to-pt full duplex because there are
only two devices on the circuit and full duplex permits either device to
transmit at any time
rarr if it is point-to-point half duplex it needs MAC and also in multipoint full
duplex configurations since several devices share the same channelrarr to ensure that no two devices attempt to transmit data at the same time
1 Controlled Access
a X-on X-off
rarrthe oldest media access control protocols dating back to the days of theteletype
b Polling
rarr the process of sending signal to a terminal to transmit or asking it to receive
rarr it uses ldquoroll call pollingrdquo with scheme or sequence
Node 3its your time to transmitNode 1 its your turn to sendNode 4 you can transmit after node 1
c Token Passing
rarrA channel accessing arrangement that is best suited for ring topology witheither a baseband or broadband network It uses a token and the token circulate in
the network
Token is an electrical signal that circulate around the ring network from onestation to another If the station has the token it can send a message
2 Contention
rarr opposite of controlled access
rarr devices wait until the circuit is free and transmit whenever it has data to send
a Carrier Sense Multiple Access with Collision Detection (CSMACD)
rarrA channel accessing method a node monitors the line to determine if the line is
busy If the station has a message to transmit but the line is busy it waits for an
idle condition before it transmits its message
Collision is the situation when two nodes transmit simultaneously using one link
Backoff Time is the ceasing time before the station attempts to transmit again
Is the process where computers on a token-ring network detect a problem and
attempt to fix it
FDDI (Fiber Distributed Data Interface)
Uses fiber-optic cable and token-passing to create a very fast reliable networkoperating at speeds of 100 Mbps
It includes up to 500 nodes over a distance of 100 km It uses ring topology with two counter-rotating rings It is implement as true physical ring topology A break in a FDDI network results in packets being sent back on the second ring
1 End system (ES) is a network device that does not perform routing or other traffic
forwarding functions Typical ESs include such devices as terminals PCs and printers
2 Intermediate System (IS) is a network device that performs routing or other traffic-forwarding functions it includes devices such as routers switches and bridges
Intradomain IS communicates within a single autonomous system Interdomain IS communicates within and between autonomous systems
3 Area is a logical group of network segments and their attached devices Areas aresubdivisions of autonomous systems
4 Autonomous System (AS) is a collection of networks under a common administrationthat share a common routing strategy Autonomous system are subdivided into areas and
It involves three phases connection establishment- a single path between the
source and the destination systems is determined data transfer ndash transmitted sequentially
over the path that has been established and connection termination ndash termination of paththat has been establish
Connectionless
Offers two important advantages over connection-oriented service dynamic path
selection ndash enables traffic to be routed around network failures because paths are selectedon a packet-to-packet basis dynamic bandwidth allocation ndash used more efficiently
because network resources are not allocated a bandwidth that they will not use
Virtual Circuits
Switched Virtual CircuitA virtual circuit that is dynamically established on demand and terminated when
transmission is completed It has three phases circuit establishment data transfer and
circuit termination
Permanent Virtual Circuit
A permanently established virtual circuit consists of one mode the data transfer
Internetworking Devices
Hubs
bull A hub is a central network device that connects network devices in a startopology
bull Advanced hubs provide very high speed connectivity for FDDI Fast Ethernet
frame relay and ATM networks
bull It is also referred to as a concentrator (or switch) which is a device that can
have multiple inputs and outputs all active at a one time
bull Services offered by hubs
bull Provide a central unit from which to connect multiple nodes into one network
bull Permit large numbers of computers to be connected on single or multipleLANs
bull Reduce network congestion through centralizing network design
bull Provide multiprotocol services such as Ethernet-to-FDDI connectivity
bull Consolidate the network backbone
bull Enable high-speed communications
bull Provide connections for several different media types
bull Multiplexers are network devices that can receive multiple inputs and transmit
them to a shared network medium
bull A multiplexer is a switch that divides a communication medium into multiple
channels so several nodes can communicate at the same time
bull A signal that is multiplexed must be demultiplexed at the other endbull Multiplexers simply are switches used in old and new technology such as the
following
Telephone switching
Switching telecommunications lines to create multiple channels on a
single line Serial communications to enable more than one terminal to
communicate over a single line Fast Ethernet X25 ISDN frame relay ATM and other networking
technologies to create multiple communication channels over a single
communications cable
bull Work at the OSI physical level switching from channel to channel using one
of three physical methods
bull Time division multiplexing (TDM)
bull Frequency division multiplexing (FDM)
bull Wavelength division multiplexing (WDM)
Bridges
A bridge is a network device that connects different LAN segments using the same accessmethod
Bridges are used to
bull To extend a LAN when the maximum connections limit has been reached
bull To extend a LAN beyond the length limit
bull To segment LANs to reduce data traffic bottlenecks
bull To prevent unauthorized access to LAN (for security)
Standby indicator Pin 36 provides the confirmation signal from the DCE in response to
select standby (pin 32)
Send common Pin 37 provides a common signal return line for unbalanced circuits from
the DTE to the DCE
Electrical Specifications
bull EIA 449 uses two other standards to define its electrical specifications
RS-423 (for unbalanced circuits) and RS-422 (for balanced circuits)
RS-423 Unbalanced Mode
bull An unbalanced circuit specification meaning that it defines only one linefor propagating a signal All signals in this standard use a common return
(or ground) to complete the circuit
RS-422 Balanced Mode
bull A balanced circuit specification meaning that it defines two lines for the propagation of each signal Signals again use a common return (or ground)
for the return of the signal In balanced mode EIA-449 utilizes both pinsin each Category I but does not use the Category II pins The ratio of data
rate to distance is much higher that that of the unbalanced standard or of
EIA-232 10 Mbps for transmission of 40 feet bull In balanced mode two lines carry the same transmission it do not carry
identical signals The signal on one line is the complement of the signal
on the other When plotted the complement looks like a mirror image ofthe original signal Instead of listening to either actual signal the receiver
detects the differences between the two This mechanism makes a balanced circuit less susceptible to noise than an unbalanced circuit and
improves performance
EIA-530
bull A version of EIA-449 that uses DB-25 pins
bull The pin functions of EIA-530 are essentially the same of EIA-449
Category I plus three pins from Category II (the loopback circuits) Other pins in EIA-232 are omitted in EIA-530 such as ring indicator signal
quality detector and data signal rate selector
X21
bull Is an interface standard designed by ITU-T to address many problems
existing in the EIA interfaces and at the same time paves the way for alldigital communications
bull A large proportion of the circuits in the EIA interfaces are used forcontrol since these are necessary to implement control functions as
separate signals With a separate line control information is represented
only by positive and negative voltages But if control signals are encoded
using a meaningful control characters from a system such as ASCII it can be transmitted over data lines
bull X21 eliminates most of the control circuits of the EIA standards and
instead directs its traffic over the data circuits To make this consolidationof functionality possible both the DTE and the DCE must have added
circuit logic that enables them to transform the control codes into bit
streams that can be sent over the data line Both also need additional logicto discriminate between control information and data upon receipt
bull Design of X21 allows not only to use fewer pins but also to be used in
digital telecommunications where control information is sent from deviceto device over a network rather than just between a DTE and a DCE
bull X21 is useful both as an interface to connect digital computers to analogdevices such as modems and as a connector between digital computers and
digital interfaces such as ISDN and X25
Byte Timing
bull Another advantage offered by X21 is that of timing lines to control bytesynchronization in addition to the bit synchronization provided by the EIA
standards By adding a byte timing pulse improves the overall
synchronization of transmissions
Control and indication
bull Pins 3 and 5 of the DB-15 connector are used for the initial handshake or
agreement to begin transmitting Pin 3 is the equivalent of request to send
Pin 5 is the equivalent of clear to send
MODEMbull Modem stands for modulatordemodulator
bull A modulator converts a digital to an analog signalbull A demodulator converts an analog signal to a digital signal
bull The series of 1s and 0s are transformed through the mechanism of ASK
FSK PSK and QAM
Transmission Rate
Bandwidth
bull Every line has upper limit and a lower limit on the frequencies of the
signals it carry this limited range is called the bandwidth
It handles connection establishment and termination data transfer
and packet creation protocols Two types of PLP packets information and control
Up to 4096 channels may be multiplexed at the PLP level Specifies protocols to handle resizing of messages
FRAME RELAY LAYERSbull A technology that operates only at the physical and datalink layers No protocol is
specified for the physical layer the choice is up to the user
bull Eliminates the extensive error checking necessary in X25 protocol
bull It uses simplified version of HDLC protocol in the datalink layerbull It uses routing and switching functions of the datalink layers Frames not packets
are switched
bull It uses PVCs (permanent virtual circuits) Identified through a DLCI (dalta linkconnection identifier)
bull A switch in frame relay performs error checking and routing Error correction is
left to the other protocols at the higher layers
bull Flow control is handled through setting the BECN (backwards explicit congestionnotification) and FECN (forward explicit congestion notification) in the address
field of the frame
bull
ASYNCHRONOUS TRANSFER MODE (ATM)
bull Is the cell relay protocol designed by the ATM forum and adopted by theITU-T
bull In ATM some software functions have moved to hardware this can
increase the data rate
Terms
Cell is the data packet is called a and is composed of 53 bytes (5 bytes of header and 48 bytes of payload) Because each cell is the same size and all are relatively small delay
and other problems associated with multiplexing different sized packets are avoided
A cell network is based on permanent virtual circuit (PVC) routing
bull Virtual Path Identifier (VPI) specifies the path a cell should take
1 Virtual path (VP) switching ndash channels within each VP remain with the VP
2 Virtual path and channel (VPC) switching ndash a channel from one VP may pass into
another VP
IXSDHSONET
Synchronous Optical Network (SONET)
Developed by ANSI
Synchronous Digital Hierarchy (SDH)
Developed by ITU-T
SONETSDH
The two are nearly identical ANSI and ITU-T defined standards that arefundamentally similar and ultimately compatible
Is a synchronous network a single clock is used to handle the timing of
transmissions and equipment across the entire network
SONET
It defines the hierarchy of signals called synchronous transport signals (STS)
Optical carrier (OC) levels are the implementation of STS
SONETSDH Rates
STS OC Rate (Mbps) STM
STS-1 OC-1 5184
STS-3 OC-3 15552 STM-1
STS-9 OC-9 46656 STM-3
STS-12 OC-12 62208 STM-4
STS-18 OC-18 93312 STM-6
STS-24 OC-24 124416 STM-8
STS-36 OC-36 186623 STM-12
STS-48 OC-48 248832 STM-16
STS-96 OC-96 497664 STM-32
STS-192 OC-192 995328 STM-64
STM-synchronous transport module
SONET Four Layers
1 Photonic layer is the lowest and performs physical layer activities
A frame at the photonic layer for STS-1 consists of 6480 bits (8000 framessec)
2-4 Section Line and Path layers correspond to the OSI modelrsquos datalink layer Eachof these layers is responsible for signal transfer across a specific portion of the
1 STS multiplexer combines several optical signals to make an STS signal2 Regenerator removes noise from optical signal
3 Adddrop multiplexer adds STS signals from different paths and removes STS signal
from a path
XTCPIP
Transmission Control ProtocolInternetworking Protocol (TCPIP)
Is a set of rules and procedures that governs the exchange of messages in an
internetwork Originally developed as a protocol for networks that wanted to be connected to
ARPANET a US Department of Defense project now known as Internet
Is a five-layer protocol suite whose bottom four layers match the OSI model fairly
closely The highest level the application layer corresponds to OSIrsquos top threelayers
Internet Protocol (IP) Is defined at the network layer
Unreliable and connectionless Is basically the set of rules for one network communicating with any other To be part of internet organization needs an internet network number unique
number to be included in any packet sent out of the network onto the internet
IP packet is known as datagram consists of a variable header and a variable data
field
IP Address
Uniquely defines the connection of a host to its network The host with more than
one IP address is multi-homed host
IP Addressing
32 bit binary number usually represented as 4 decimal values Equivalent to 4 octets ( 8 bits each decimal value ) Dotted decimal notation Consists of 2 parts the network and the node
Network ndash identifier of particular network on the internet
Host ndash identifier of a particular device which can be a server or a
A frame is an information unit whose source and destination are datalink layer entities A
frame is composed of the datalink layer header (and possibly a trailer) and upper-layer
data The header and the trailer contain control information intended for the data-link
layer entity in the destination system
A packet is an information unit whose source and destination are network-layer entities
A packet is composed of the network-layer header (and possibly a trailer0 and upper-layer data The header and the trailer contain control information intended for the
network-layer entity in the destination system The data from upper-layer entities is
encapsulated in the network-layer header and trailer
The term datagram usually refers to an information unit whose source and destination
are network-layer entities that use connectionless network services
The term segment usually refers to an information unit whose source and destination aretransport layer entities
A message is an information unit whose source and destination entities exist above the
network layer (often the application layer)
A cell is an information unit of a fixed size whose source and destination are datalink
layer entities Cells are used in switched environments such as ATM and SMDS A cell
is composed of the header and payload The header contains control informationintended for the destination datalink layer entity and is typically 5 bytes long The
payload contains upper-layer data that is encapsulated in the cell header and typically 48 bytes long
Data unit is a generic term that refers to a variety of information units Some commondata units are service data units (SDU) protocol data units (PDU) and bridge protocol
data units (BPDU) SDUs are information units from upper-layer protocols that define a
service request to a lower-layer protocol PDU is OSI terminology for a packet BPDUS
are used by the spanning-tree algorithm as hello messages
Three Basic elements in Layer Services
1 Service User is the OSI layer that requests services from an adjacent OSI layer
2 Service Provider is the OSI layer that provides services to service users
3 Service Access Point is a conceptual location at which one OSI layer can request the
Peer-to-peer ndash all nodes has equal authority in the networkClient-server ndash a certain node called server has full control over the network and
nodes in the network
LAN Components
1 Server
Is a computer in a network that shared by multiple users
2 Network Interface Card
A printed circuit board that plugs into a network server or client computer It
enables the computer to be physically connected to the network cable which provides the
physical layer connection among the computers in the network It performs electronicfunctions of the access method or datalink protocol
3 HubA device that acts as central connection of certain LAN topology It is capable of
regeneration and switching of signals from one node to another Also known as
concentrator multiple access unit transceiver or repeater
4 Cable
The transmission link in a network These are unshielded twisted pairs (UTP)
shielded twisted pair (STP) coaxial cable and fiber optics cable
5 Connector
The terminating end of the cable to be plug-in or connected to the device
6 Network Operating System (NOS)
The control program that resides in a server or workstation within a LAN Ithandles requests for data transfer from all the users of the networks It interact with the
application programs and the computerrsquos operating system
7 Client
It is the requesting computer from the supplying computers or server
8 Other Peripheral Devices
These are the devices attached to the network such as printers scanners and the
LAN Access Methodrarr it is unnecessary to have a MAC in pt-to-pt full duplex because there are
only two devices on the circuit and full duplex permits either device to
transmit at any time
rarr if it is point-to-point half duplex it needs MAC and also in multipoint full
duplex configurations since several devices share the same channelrarr to ensure that no two devices attempt to transmit data at the same time
1 Controlled Access
a X-on X-off
rarrthe oldest media access control protocols dating back to the days of theteletype
b Polling
rarr the process of sending signal to a terminal to transmit or asking it to receive
rarr it uses ldquoroll call pollingrdquo with scheme or sequence
Node 3its your time to transmitNode 1 its your turn to sendNode 4 you can transmit after node 1
c Token Passing
rarrA channel accessing arrangement that is best suited for ring topology witheither a baseband or broadband network It uses a token and the token circulate in
the network
Token is an electrical signal that circulate around the ring network from onestation to another If the station has the token it can send a message
2 Contention
rarr opposite of controlled access
rarr devices wait until the circuit is free and transmit whenever it has data to send
a Carrier Sense Multiple Access with Collision Detection (CSMACD)
rarrA channel accessing method a node monitors the line to determine if the line is
busy If the station has a message to transmit but the line is busy it waits for an
idle condition before it transmits its message
Collision is the situation when two nodes transmit simultaneously using one link
Backoff Time is the ceasing time before the station attempts to transmit again
Is the process where computers on a token-ring network detect a problem and
attempt to fix it
FDDI (Fiber Distributed Data Interface)
Uses fiber-optic cable and token-passing to create a very fast reliable networkoperating at speeds of 100 Mbps
It includes up to 500 nodes over a distance of 100 km It uses ring topology with two counter-rotating rings It is implement as true physical ring topology A break in a FDDI network results in packets being sent back on the second ring
1 End system (ES) is a network device that does not perform routing or other traffic
forwarding functions Typical ESs include such devices as terminals PCs and printers
2 Intermediate System (IS) is a network device that performs routing or other traffic-forwarding functions it includes devices such as routers switches and bridges
Intradomain IS communicates within a single autonomous system Interdomain IS communicates within and between autonomous systems
3 Area is a logical group of network segments and their attached devices Areas aresubdivisions of autonomous systems
4 Autonomous System (AS) is a collection of networks under a common administrationthat share a common routing strategy Autonomous system are subdivided into areas and
It involves three phases connection establishment- a single path between the
source and the destination systems is determined data transfer ndash transmitted sequentially
over the path that has been established and connection termination ndash termination of paththat has been establish
Connectionless
Offers two important advantages over connection-oriented service dynamic path
selection ndash enables traffic to be routed around network failures because paths are selectedon a packet-to-packet basis dynamic bandwidth allocation ndash used more efficiently
because network resources are not allocated a bandwidth that they will not use
Virtual Circuits
Switched Virtual CircuitA virtual circuit that is dynamically established on demand and terminated when
transmission is completed It has three phases circuit establishment data transfer and
circuit termination
Permanent Virtual Circuit
A permanently established virtual circuit consists of one mode the data transfer
Internetworking Devices
Hubs
bull A hub is a central network device that connects network devices in a startopology
bull Advanced hubs provide very high speed connectivity for FDDI Fast Ethernet
frame relay and ATM networks
bull It is also referred to as a concentrator (or switch) which is a device that can
have multiple inputs and outputs all active at a one time
bull Services offered by hubs
bull Provide a central unit from which to connect multiple nodes into one network
bull Permit large numbers of computers to be connected on single or multipleLANs
bull Reduce network congestion through centralizing network design
bull Provide multiprotocol services such as Ethernet-to-FDDI connectivity
bull Consolidate the network backbone
bull Enable high-speed communications
bull Provide connections for several different media types
bull Multiplexers are network devices that can receive multiple inputs and transmit
them to a shared network medium
bull A multiplexer is a switch that divides a communication medium into multiple
channels so several nodes can communicate at the same time
bull A signal that is multiplexed must be demultiplexed at the other endbull Multiplexers simply are switches used in old and new technology such as the
following
Telephone switching
Switching telecommunications lines to create multiple channels on a
single line Serial communications to enable more than one terminal to
communicate over a single line Fast Ethernet X25 ISDN frame relay ATM and other networking
technologies to create multiple communication channels over a single
communications cable
bull Work at the OSI physical level switching from channel to channel using one
of three physical methods
bull Time division multiplexing (TDM)
bull Frequency division multiplexing (FDM)
bull Wavelength division multiplexing (WDM)
Bridges
A bridge is a network device that connects different LAN segments using the same accessmethod
Bridges are used to
bull To extend a LAN when the maximum connections limit has been reached
bull To extend a LAN beyond the length limit
bull To segment LANs to reduce data traffic bottlenecks
bull To prevent unauthorized access to LAN (for security)
Standby indicator Pin 36 provides the confirmation signal from the DCE in response to
select standby (pin 32)
Send common Pin 37 provides a common signal return line for unbalanced circuits from
the DTE to the DCE
Electrical Specifications
bull EIA 449 uses two other standards to define its electrical specifications
RS-423 (for unbalanced circuits) and RS-422 (for balanced circuits)
RS-423 Unbalanced Mode
bull An unbalanced circuit specification meaning that it defines only one linefor propagating a signal All signals in this standard use a common return
(or ground) to complete the circuit
RS-422 Balanced Mode
bull A balanced circuit specification meaning that it defines two lines for the propagation of each signal Signals again use a common return (or ground)
for the return of the signal In balanced mode EIA-449 utilizes both pinsin each Category I but does not use the Category II pins The ratio of data
rate to distance is much higher that that of the unbalanced standard or of
EIA-232 10 Mbps for transmission of 40 feet bull In balanced mode two lines carry the same transmission it do not carry
identical signals The signal on one line is the complement of the signal
on the other When plotted the complement looks like a mirror image ofthe original signal Instead of listening to either actual signal the receiver
detects the differences between the two This mechanism makes a balanced circuit less susceptible to noise than an unbalanced circuit and
improves performance
EIA-530
bull A version of EIA-449 that uses DB-25 pins
bull The pin functions of EIA-530 are essentially the same of EIA-449
Category I plus three pins from Category II (the loopback circuits) Other pins in EIA-232 are omitted in EIA-530 such as ring indicator signal
quality detector and data signal rate selector
X21
bull Is an interface standard designed by ITU-T to address many problems
existing in the EIA interfaces and at the same time paves the way for alldigital communications
bull A large proportion of the circuits in the EIA interfaces are used forcontrol since these are necessary to implement control functions as
separate signals With a separate line control information is represented
only by positive and negative voltages But if control signals are encoded
using a meaningful control characters from a system such as ASCII it can be transmitted over data lines
bull X21 eliminates most of the control circuits of the EIA standards and
instead directs its traffic over the data circuits To make this consolidationof functionality possible both the DTE and the DCE must have added
circuit logic that enables them to transform the control codes into bit
streams that can be sent over the data line Both also need additional logicto discriminate between control information and data upon receipt
bull Design of X21 allows not only to use fewer pins but also to be used in
digital telecommunications where control information is sent from deviceto device over a network rather than just between a DTE and a DCE
bull X21 is useful both as an interface to connect digital computers to analogdevices such as modems and as a connector between digital computers and
digital interfaces such as ISDN and X25
Byte Timing
bull Another advantage offered by X21 is that of timing lines to control bytesynchronization in addition to the bit synchronization provided by the EIA
standards By adding a byte timing pulse improves the overall
synchronization of transmissions
Control and indication
bull Pins 3 and 5 of the DB-15 connector are used for the initial handshake or
agreement to begin transmitting Pin 3 is the equivalent of request to send
Pin 5 is the equivalent of clear to send
MODEMbull Modem stands for modulatordemodulator
bull A modulator converts a digital to an analog signalbull A demodulator converts an analog signal to a digital signal
bull The series of 1s and 0s are transformed through the mechanism of ASK
FSK PSK and QAM
Transmission Rate
Bandwidth
bull Every line has upper limit and a lower limit on the frequencies of the
signals it carry this limited range is called the bandwidth
It handles connection establishment and termination data transfer
and packet creation protocols Two types of PLP packets information and control
Up to 4096 channels may be multiplexed at the PLP level Specifies protocols to handle resizing of messages
FRAME RELAY LAYERSbull A technology that operates only at the physical and datalink layers No protocol is
specified for the physical layer the choice is up to the user
bull Eliminates the extensive error checking necessary in X25 protocol
bull It uses simplified version of HDLC protocol in the datalink layerbull It uses routing and switching functions of the datalink layers Frames not packets
are switched
bull It uses PVCs (permanent virtual circuits) Identified through a DLCI (dalta linkconnection identifier)
bull A switch in frame relay performs error checking and routing Error correction is
left to the other protocols at the higher layers
bull Flow control is handled through setting the BECN (backwards explicit congestionnotification) and FECN (forward explicit congestion notification) in the address
field of the frame
bull
ASYNCHRONOUS TRANSFER MODE (ATM)
bull Is the cell relay protocol designed by the ATM forum and adopted by theITU-T
bull In ATM some software functions have moved to hardware this can
increase the data rate
Terms
Cell is the data packet is called a and is composed of 53 bytes (5 bytes of header and 48 bytes of payload) Because each cell is the same size and all are relatively small delay
and other problems associated with multiplexing different sized packets are avoided
A cell network is based on permanent virtual circuit (PVC) routing
bull Virtual Path Identifier (VPI) specifies the path a cell should take
1 Virtual path (VP) switching ndash channels within each VP remain with the VP
2 Virtual path and channel (VPC) switching ndash a channel from one VP may pass into
another VP
IXSDHSONET
Synchronous Optical Network (SONET)
Developed by ANSI
Synchronous Digital Hierarchy (SDH)
Developed by ITU-T
SONETSDH
The two are nearly identical ANSI and ITU-T defined standards that arefundamentally similar and ultimately compatible
Is a synchronous network a single clock is used to handle the timing of
transmissions and equipment across the entire network
SONET
It defines the hierarchy of signals called synchronous transport signals (STS)
Optical carrier (OC) levels are the implementation of STS
SONETSDH Rates
STS OC Rate (Mbps) STM
STS-1 OC-1 5184
STS-3 OC-3 15552 STM-1
STS-9 OC-9 46656 STM-3
STS-12 OC-12 62208 STM-4
STS-18 OC-18 93312 STM-6
STS-24 OC-24 124416 STM-8
STS-36 OC-36 186623 STM-12
STS-48 OC-48 248832 STM-16
STS-96 OC-96 497664 STM-32
STS-192 OC-192 995328 STM-64
STM-synchronous transport module
SONET Four Layers
1 Photonic layer is the lowest and performs physical layer activities
A frame at the photonic layer for STS-1 consists of 6480 bits (8000 framessec)
2-4 Section Line and Path layers correspond to the OSI modelrsquos datalink layer Eachof these layers is responsible for signal transfer across a specific portion of the
1 STS multiplexer combines several optical signals to make an STS signal2 Regenerator removes noise from optical signal
3 Adddrop multiplexer adds STS signals from different paths and removes STS signal
from a path
XTCPIP
Transmission Control ProtocolInternetworking Protocol (TCPIP)
Is a set of rules and procedures that governs the exchange of messages in an
internetwork Originally developed as a protocol for networks that wanted to be connected to
ARPANET a US Department of Defense project now known as Internet
Is a five-layer protocol suite whose bottom four layers match the OSI model fairly
closely The highest level the application layer corresponds to OSIrsquos top threelayers
Internet Protocol (IP) Is defined at the network layer
Unreliable and connectionless Is basically the set of rules for one network communicating with any other To be part of internet organization needs an internet network number unique
number to be included in any packet sent out of the network onto the internet
IP packet is known as datagram consists of a variable header and a variable data
field
IP Address
Uniquely defines the connection of a host to its network The host with more than
one IP address is multi-homed host
IP Addressing
32 bit binary number usually represented as 4 decimal values Equivalent to 4 octets ( 8 bits each decimal value ) Dotted decimal notation Consists of 2 parts the network and the node
Network ndash identifier of particular network on the internet
Host ndash identifier of a particular device which can be a server or a
A frame is an information unit whose source and destination are datalink layer entities A
frame is composed of the datalink layer header (and possibly a trailer) and upper-layer
data The header and the trailer contain control information intended for the data-link
layer entity in the destination system
A packet is an information unit whose source and destination are network-layer entities
A packet is composed of the network-layer header (and possibly a trailer0 and upper-layer data The header and the trailer contain control information intended for the
network-layer entity in the destination system The data from upper-layer entities is
encapsulated in the network-layer header and trailer
The term datagram usually refers to an information unit whose source and destination
are network-layer entities that use connectionless network services
The term segment usually refers to an information unit whose source and destination aretransport layer entities
A message is an information unit whose source and destination entities exist above the
network layer (often the application layer)
A cell is an information unit of a fixed size whose source and destination are datalink
layer entities Cells are used in switched environments such as ATM and SMDS A cell
is composed of the header and payload The header contains control informationintended for the destination datalink layer entity and is typically 5 bytes long The
payload contains upper-layer data that is encapsulated in the cell header and typically 48 bytes long
Data unit is a generic term that refers to a variety of information units Some commondata units are service data units (SDU) protocol data units (PDU) and bridge protocol
data units (BPDU) SDUs are information units from upper-layer protocols that define a
service request to a lower-layer protocol PDU is OSI terminology for a packet BPDUS
are used by the spanning-tree algorithm as hello messages
Three Basic elements in Layer Services
1 Service User is the OSI layer that requests services from an adjacent OSI layer
2 Service Provider is the OSI layer that provides services to service users
3 Service Access Point is a conceptual location at which one OSI layer can request the
Peer-to-peer ndash all nodes has equal authority in the networkClient-server ndash a certain node called server has full control over the network and
nodes in the network
LAN Components
1 Server
Is a computer in a network that shared by multiple users
2 Network Interface Card
A printed circuit board that plugs into a network server or client computer It
enables the computer to be physically connected to the network cable which provides the
physical layer connection among the computers in the network It performs electronicfunctions of the access method or datalink protocol
3 HubA device that acts as central connection of certain LAN topology It is capable of
regeneration and switching of signals from one node to another Also known as
concentrator multiple access unit transceiver or repeater
4 Cable
The transmission link in a network These are unshielded twisted pairs (UTP)
shielded twisted pair (STP) coaxial cable and fiber optics cable
5 Connector
The terminating end of the cable to be plug-in or connected to the device
6 Network Operating System (NOS)
The control program that resides in a server or workstation within a LAN Ithandles requests for data transfer from all the users of the networks It interact with the
application programs and the computerrsquos operating system
7 Client
It is the requesting computer from the supplying computers or server
8 Other Peripheral Devices
These are the devices attached to the network such as printers scanners and the
LAN Access Methodrarr it is unnecessary to have a MAC in pt-to-pt full duplex because there are
only two devices on the circuit and full duplex permits either device to
transmit at any time
rarr if it is point-to-point half duplex it needs MAC and also in multipoint full
duplex configurations since several devices share the same channelrarr to ensure that no two devices attempt to transmit data at the same time
1 Controlled Access
a X-on X-off
rarrthe oldest media access control protocols dating back to the days of theteletype
b Polling
rarr the process of sending signal to a terminal to transmit or asking it to receive
rarr it uses ldquoroll call pollingrdquo with scheme or sequence
Node 3its your time to transmitNode 1 its your turn to sendNode 4 you can transmit after node 1
c Token Passing
rarrA channel accessing arrangement that is best suited for ring topology witheither a baseband or broadband network It uses a token and the token circulate in
the network
Token is an electrical signal that circulate around the ring network from onestation to another If the station has the token it can send a message
2 Contention
rarr opposite of controlled access
rarr devices wait until the circuit is free and transmit whenever it has data to send
a Carrier Sense Multiple Access with Collision Detection (CSMACD)
rarrA channel accessing method a node monitors the line to determine if the line is
busy If the station has a message to transmit but the line is busy it waits for an
idle condition before it transmits its message
Collision is the situation when two nodes transmit simultaneously using one link
Backoff Time is the ceasing time before the station attempts to transmit again
Is the process where computers on a token-ring network detect a problem and
attempt to fix it
FDDI (Fiber Distributed Data Interface)
Uses fiber-optic cable and token-passing to create a very fast reliable networkoperating at speeds of 100 Mbps
It includes up to 500 nodes over a distance of 100 km It uses ring topology with two counter-rotating rings It is implement as true physical ring topology A break in a FDDI network results in packets being sent back on the second ring
1 End system (ES) is a network device that does not perform routing or other traffic
forwarding functions Typical ESs include such devices as terminals PCs and printers
2 Intermediate System (IS) is a network device that performs routing or other traffic-forwarding functions it includes devices such as routers switches and bridges
Intradomain IS communicates within a single autonomous system Interdomain IS communicates within and between autonomous systems
3 Area is a logical group of network segments and their attached devices Areas aresubdivisions of autonomous systems
4 Autonomous System (AS) is a collection of networks under a common administrationthat share a common routing strategy Autonomous system are subdivided into areas and
It involves three phases connection establishment- a single path between the
source and the destination systems is determined data transfer ndash transmitted sequentially
over the path that has been established and connection termination ndash termination of paththat has been establish
Connectionless
Offers two important advantages over connection-oriented service dynamic path
selection ndash enables traffic to be routed around network failures because paths are selectedon a packet-to-packet basis dynamic bandwidth allocation ndash used more efficiently
because network resources are not allocated a bandwidth that they will not use
Virtual Circuits
Switched Virtual CircuitA virtual circuit that is dynamically established on demand and terminated when
transmission is completed It has three phases circuit establishment data transfer and
circuit termination
Permanent Virtual Circuit
A permanently established virtual circuit consists of one mode the data transfer
Internetworking Devices
Hubs
bull A hub is a central network device that connects network devices in a startopology
bull Advanced hubs provide very high speed connectivity for FDDI Fast Ethernet
frame relay and ATM networks
bull It is also referred to as a concentrator (or switch) which is a device that can
have multiple inputs and outputs all active at a one time
bull Services offered by hubs
bull Provide a central unit from which to connect multiple nodes into one network
bull Permit large numbers of computers to be connected on single or multipleLANs
bull Reduce network congestion through centralizing network design
bull Provide multiprotocol services such as Ethernet-to-FDDI connectivity
bull Consolidate the network backbone
bull Enable high-speed communications
bull Provide connections for several different media types
bull Multiplexers are network devices that can receive multiple inputs and transmit
them to a shared network medium
bull A multiplexer is a switch that divides a communication medium into multiple
channels so several nodes can communicate at the same time
bull A signal that is multiplexed must be demultiplexed at the other endbull Multiplexers simply are switches used in old and new technology such as the
following
Telephone switching
Switching telecommunications lines to create multiple channels on a
single line Serial communications to enable more than one terminal to
communicate over a single line Fast Ethernet X25 ISDN frame relay ATM and other networking
technologies to create multiple communication channels over a single
communications cable
bull Work at the OSI physical level switching from channel to channel using one
of three physical methods
bull Time division multiplexing (TDM)
bull Frequency division multiplexing (FDM)
bull Wavelength division multiplexing (WDM)
Bridges
A bridge is a network device that connects different LAN segments using the same accessmethod
Bridges are used to
bull To extend a LAN when the maximum connections limit has been reached
bull To extend a LAN beyond the length limit
bull To segment LANs to reduce data traffic bottlenecks
bull To prevent unauthorized access to LAN (for security)
Standby indicator Pin 36 provides the confirmation signal from the DCE in response to
select standby (pin 32)
Send common Pin 37 provides a common signal return line for unbalanced circuits from
the DTE to the DCE
Electrical Specifications
bull EIA 449 uses two other standards to define its electrical specifications
RS-423 (for unbalanced circuits) and RS-422 (for balanced circuits)
RS-423 Unbalanced Mode
bull An unbalanced circuit specification meaning that it defines only one linefor propagating a signal All signals in this standard use a common return
(or ground) to complete the circuit
RS-422 Balanced Mode
bull A balanced circuit specification meaning that it defines two lines for the propagation of each signal Signals again use a common return (or ground)
for the return of the signal In balanced mode EIA-449 utilizes both pinsin each Category I but does not use the Category II pins The ratio of data
rate to distance is much higher that that of the unbalanced standard or of
EIA-232 10 Mbps for transmission of 40 feet bull In balanced mode two lines carry the same transmission it do not carry
identical signals The signal on one line is the complement of the signal
on the other When plotted the complement looks like a mirror image ofthe original signal Instead of listening to either actual signal the receiver
detects the differences between the two This mechanism makes a balanced circuit less susceptible to noise than an unbalanced circuit and
improves performance
EIA-530
bull A version of EIA-449 that uses DB-25 pins
bull The pin functions of EIA-530 are essentially the same of EIA-449
Category I plus three pins from Category II (the loopback circuits) Other pins in EIA-232 are omitted in EIA-530 such as ring indicator signal
quality detector and data signal rate selector
X21
bull Is an interface standard designed by ITU-T to address many problems
existing in the EIA interfaces and at the same time paves the way for alldigital communications
bull A large proportion of the circuits in the EIA interfaces are used forcontrol since these are necessary to implement control functions as
separate signals With a separate line control information is represented
only by positive and negative voltages But if control signals are encoded
using a meaningful control characters from a system such as ASCII it can be transmitted over data lines
bull X21 eliminates most of the control circuits of the EIA standards and
instead directs its traffic over the data circuits To make this consolidationof functionality possible both the DTE and the DCE must have added
circuit logic that enables them to transform the control codes into bit
streams that can be sent over the data line Both also need additional logicto discriminate between control information and data upon receipt
bull Design of X21 allows not only to use fewer pins but also to be used in
digital telecommunications where control information is sent from deviceto device over a network rather than just between a DTE and a DCE
bull X21 is useful both as an interface to connect digital computers to analogdevices such as modems and as a connector between digital computers and
digital interfaces such as ISDN and X25
Byte Timing
bull Another advantage offered by X21 is that of timing lines to control bytesynchronization in addition to the bit synchronization provided by the EIA
standards By adding a byte timing pulse improves the overall
synchronization of transmissions
Control and indication
bull Pins 3 and 5 of the DB-15 connector are used for the initial handshake or
agreement to begin transmitting Pin 3 is the equivalent of request to send
Pin 5 is the equivalent of clear to send
MODEMbull Modem stands for modulatordemodulator
bull A modulator converts a digital to an analog signalbull A demodulator converts an analog signal to a digital signal
bull The series of 1s and 0s are transformed through the mechanism of ASK
FSK PSK and QAM
Transmission Rate
Bandwidth
bull Every line has upper limit and a lower limit on the frequencies of the
signals it carry this limited range is called the bandwidth
It handles connection establishment and termination data transfer
and packet creation protocols Two types of PLP packets information and control
Up to 4096 channels may be multiplexed at the PLP level Specifies protocols to handle resizing of messages
FRAME RELAY LAYERSbull A technology that operates only at the physical and datalink layers No protocol is
specified for the physical layer the choice is up to the user
bull Eliminates the extensive error checking necessary in X25 protocol
bull It uses simplified version of HDLC protocol in the datalink layerbull It uses routing and switching functions of the datalink layers Frames not packets
are switched
bull It uses PVCs (permanent virtual circuits) Identified through a DLCI (dalta linkconnection identifier)
bull A switch in frame relay performs error checking and routing Error correction is
left to the other protocols at the higher layers
bull Flow control is handled through setting the BECN (backwards explicit congestionnotification) and FECN (forward explicit congestion notification) in the address
field of the frame
bull
ASYNCHRONOUS TRANSFER MODE (ATM)
bull Is the cell relay protocol designed by the ATM forum and adopted by theITU-T
bull In ATM some software functions have moved to hardware this can
increase the data rate
Terms
Cell is the data packet is called a and is composed of 53 bytes (5 bytes of header and 48 bytes of payload) Because each cell is the same size and all are relatively small delay
and other problems associated with multiplexing different sized packets are avoided
A cell network is based on permanent virtual circuit (PVC) routing
bull Virtual Path Identifier (VPI) specifies the path a cell should take
1 Virtual path (VP) switching ndash channels within each VP remain with the VP
2 Virtual path and channel (VPC) switching ndash a channel from one VP may pass into
another VP
IXSDHSONET
Synchronous Optical Network (SONET)
Developed by ANSI
Synchronous Digital Hierarchy (SDH)
Developed by ITU-T
SONETSDH
The two are nearly identical ANSI and ITU-T defined standards that arefundamentally similar and ultimately compatible
Is a synchronous network a single clock is used to handle the timing of
transmissions and equipment across the entire network
SONET
It defines the hierarchy of signals called synchronous transport signals (STS)
Optical carrier (OC) levels are the implementation of STS
SONETSDH Rates
STS OC Rate (Mbps) STM
STS-1 OC-1 5184
STS-3 OC-3 15552 STM-1
STS-9 OC-9 46656 STM-3
STS-12 OC-12 62208 STM-4
STS-18 OC-18 93312 STM-6
STS-24 OC-24 124416 STM-8
STS-36 OC-36 186623 STM-12
STS-48 OC-48 248832 STM-16
STS-96 OC-96 497664 STM-32
STS-192 OC-192 995328 STM-64
STM-synchronous transport module
SONET Four Layers
1 Photonic layer is the lowest and performs physical layer activities
A frame at the photonic layer for STS-1 consists of 6480 bits (8000 framessec)
2-4 Section Line and Path layers correspond to the OSI modelrsquos datalink layer Eachof these layers is responsible for signal transfer across a specific portion of the
1 STS multiplexer combines several optical signals to make an STS signal2 Regenerator removes noise from optical signal
3 Adddrop multiplexer adds STS signals from different paths and removes STS signal
from a path
XTCPIP
Transmission Control ProtocolInternetworking Protocol (TCPIP)
Is a set of rules and procedures that governs the exchange of messages in an
internetwork Originally developed as a protocol for networks that wanted to be connected to
ARPANET a US Department of Defense project now known as Internet
Is a five-layer protocol suite whose bottom four layers match the OSI model fairly
closely The highest level the application layer corresponds to OSIrsquos top threelayers
Internet Protocol (IP) Is defined at the network layer
Unreliable and connectionless Is basically the set of rules for one network communicating with any other To be part of internet organization needs an internet network number unique
number to be included in any packet sent out of the network onto the internet
IP packet is known as datagram consists of a variable header and a variable data
field
IP Address
Uniquely defines the connection of a host to its network The host with more than
one IP address is multi-homed host
IP Addressing
32 bit binary number usually represented as 4 decimal values Equivalent to 4 octets ( 8 bits each decimal value ) Dotted decimal notation Consists of 2 parts the network and the node
Network ndash identifier of particular network on the internet
Host ndash identifier of a particular device which can be a server or a
A frame is an information unit whose source and destination are datalink layer entities A
frame is composed of the datalink layer header (and possibly a trailer) and upper-layer
data The header and the trailer contain control information intended for the data-link
layer entity in the destination system
A packet is an information unit whose source and destination are network-layer entities
A packet is composed of the network-layer header (and possibly a trailer0 and upper-layer data The header and the trailer contain control information intended for the
network-layer entity in the destination system The data from upper-layer entities is
encapsulated in the network-layer header and trailer
The term datagram usually refers to an information unit whose source and destination
are network-layer entities that use connectionless network services
The term segment usually refers to an information unit whose source and destination aretransport layer entities
A message is an information unit whose source and destination entities exist above the
network layer (often the application layer)
A cell is an information unit of a fixed size whose source and destination are datalink
layer entities Cells are used in switched environments such as ATM and SMDS A cell
is composed of the header and payload The header contains control informationintended for the destination datalink layer entity and is typically 5 bytes long The
payload contains upper-layer data that is encapsulated in the cell header and typically 48 bytes long
Data unit is a generic term that refers to a variety of information units Some commondata units are service data units (SDU) protocol data units (PDU) and bridge protocol
data units (BPDU) SDUs are information units from upper-layer protocols that define a
service request to a lower-layer protocol PDU is OSI terminology for a packet BPDUS
are used by the spanning-tree algorithm as hello messages
Three Basic elements in Layer Services
1 Service User is the OSI layer that requests services from an adjacent OSI layer
2 Service Provider is the OSI layer that provides services to service users
3 Service Access Point is a conceptual location at which one OSI layer can request the
Peer-to-peer ndash all nodes has equal authority in the networkClient-server ndash a certain node called server has full control over the network and
nodes in the network
LAN Components
1 Server
Is a computer in a network that shared by multiple users
2 Network Interface Card
A printed circuit board that plugs into a network server or client computer It
enables the computer to be physically connected to the network cable which provides the
physical layer connection among the computers in the network It performs electronicfunctions of the access method or datalink protocol
3 HubA device that acts as central connection of certain LAN topology It is capable of
regeneration and switching of signals from one node to another Also known as
concentrator multiple access unit transceiver or repeater
4 Cable
The transmission link in a network These are unshielded twisted pairs (UTP)
shielded twisted pair (STP) coaxial cable and fiber optics cable
5 Connector
The terminating end of the cable to be plug-in or connected to the device
6 Network Operating System (NOS)
The control program that resides in a server or workstation within a LAN Ithandles requests for data transfer from all the users of the networks It interact with the
application programs and the computerrsquos operating system
7 Client
It is the requesting computer from the supplying computers or server
8 Other Peripheral Devices
These are the devices attached to the network such as printers scanners and the
LAN Access Methodrarr it is unnecessary to have a MAC in pt-to-pt full duplex because there are
only two devices on the circuit and full duplex permits either device to
transmit at any time
rarr if it is point-to-point half duplex it needs MAC and also in multipoint full
duplex configurations since several devices share the same channelrarr to ensure that no two devices attempt to transmit data at the same time
1 Controlled Access
a X-on X-off
rarrthe oldest media access control protocols dating back to the days of theteletype
b Polling
rarr the process of sending signal to a terminal to transmit or asking it to receive
rarr it uses ldquoroll call pollingrdquo with scheme or sequence
Node 3its your time to transmitNode 1 its your turn to sendNode 4 you can transmit after node 1
c Token Passing
rarrA channel accessing arrangement that is best suited for ring topology witheither a baseband or broadband network It uses a token and the token circulate in
the network
Token is an electrical signal that circulate around the ring network from onestation to another If the station has the token it can send a message
2 Contention
rarr opposite of controlled access
rarr devices wait until the circuit is free and transmit whenever it has data to send
a Carrier Sense Multiple Access with Collision Detection (CSMACD)
rarrA channel accessing method a node monitors the line to determine if the line is
busy If the station has a message to transmit but the line is busy it waits for an
idle condition before it transmits its message
Collision is the situation when two nodes transmit simultaneously using one link
Backoff Time is the ceasing time before the station attempts to transmit again
Is the process where computers on a token-ring network detect a problem and
attempt to fix it
FDDI (Fiber Distributed Data Interface)
Uses fiber-optic cable and token-passing to create a very fast reliable networkoperating at speeds of 100 Mbps
It includes up to 500 nodes over a distance of 100 km It uses ring topology with two counter-rotating rings It is implement as true physical ring topology A break in a FDDI network results in packets being sent back on the second ring
1 End system (ES) is a network device that does not perform routing or other traffic
forwarding functions Typical ESs include such devices as terminals PCs and printers
2 Intermediate System (IS) is a network device that performs routing or other traffic-forwarding functions it includes devices such as routers switches and bridges
Intradomain IS communicates within a single autonomous system Interdomain IS communicates within and between autonomous systems
3 Area is a logical group of network segments and their attached devices Areas aresubdivisions of autonomous systems
4 Autonomous System (AS) is a collection of networks under a common administrationthat share a common routing strategy Autonomous system are subdivided into areas and
It involves three phases connection establishment- a single path between the
source and the destination systems is determined data transfer ndash transmitted sequentially
over the path that has been established and connection termination ndash termination of paththat has been establish
Connectionless
Offers two important advantages over connection-oriented service dynamic path
selection ndash enables traffic to be routed around network failures because paths are selectedon a packet-to-packet basis dynamic bandwidth allocation ndash used more efficiently
because network resources are not allocated a bandwidth that they will not use
Virtual Circuits
Switched Virtual CircuitA virtual circuit that is dynamically established on demand and terminated when
transmission is completed It has three phases circuit establishment data transfer and
circuit termination
Permanent Virtual Circuit
A permanently established virtual circuit consists of one mode the data transfer
Internetworking Devices
Hubs
bull A hub is a central network device that connects network devices in a startopology
bull Advanced hubs provide very high speed connectivity for FDDI Fast Ethernet
frame relay and ATM networks
bull It is also referred to as a concentrator (or switch) which is a device that can
have multiple inputs and outputs all active at a one time
bull Services offered by hubs
bull Provide a central unit from which to connect multiple nodes into one network
bull Permit large numbers of computers to be connected on single or multipleLANs
bull Reduce network congestion through centralizing network design
bull Provide multiprotocol services such as Ethernet-to-FDDI connectivity
bull Consolidate the network backbone
bull Enable high-speed communications
bull Provide connections for several different media types
bull Multiplexers are network devices that can receive multiple inputs and transmit
them to a shared network medium
bull A multiplexer is a switch that divides a communication medium into multiple
channels so several nodes can communicate at the same time
bull A signal that is multiplexed must be demultiplexed at the other endbull Multiplexers simply are switches used in old and new technology such as the
following
Telephone switching
Switching telecommunications lines to create multiple channels on a
single line Serial communications to enable more than one terminal to
communicate over a single line Fast Ethernet X25 ISDN frame relay ATM and other networking
technologies to create multiple communication channels over a single
communications cable
bull Work at the OSI physical level switching from channel to channel using one
of three physical methods
bull Time division multiplexing (TDM)
bull Frequency division multiplexing (FDM)
bull Wavelength division multiplexing (WDM)
Bridges
A bridge is a network device that connects different LAN segments using the same accessmethod
Bridges are used to
bull To extend a LAN when the maximum connections limit has been reached
bull To extend a LAN beyond the length limit
bull To segment LANs to reduce data traffic bottlenecks
bull To prevent unauthorized access to LAN (for security)
Standby indicator Pin 36 provides the confirmation signal from the DCE in response to
select standby (pin 32)
Send common Pin 37 provides a common signal return line for unbalanced circuits from
the DTE to the DCE
Electrical Specifications
bull EIA 449 uses two other standards to define its electrical specifications
RS-423 (for unbalanced circuits) and RS-422 (for balanced circuits)
RS-423 Unbalanced Mode
bull An unbalanced circuit specification meaning that it defines only one linefor propagating a signal All signals in this standard use a common return
(or ground) to complete the circuit
RS-422 Balanced Mode
bull A balanced circuit specification meaning that it defines two lines for the propagation of each signal Signals again use a common return (or ground)
for the return of the signal In balanced mode EIA-449 utilizes both pinsin each Category I but does not use the Category II pins The ratio of data
rate to distance is much higher that that of the unbalanced standard or of
EIA-232 10 Mbps for transmission of 40 feet bull In balanced mode two lines carry the same transmission it do not carry
identical signals The signal on one line is the complement of the signal
on the other When plotted the complement looks like a mirror image ofthe original signal Instead of listening to either actual signal the receiver
detects the differences between the two This mechanism makes a balanced circuit less susceptible to noise than an unbalanced circuit and
improves performance
EIA-530
bull A version of EIA-449 that uses DB-25 pins
bull The pin functions of EIA-530 are essentially the same of EIA-449
Category I plus three pins from Category II (the loopback circuits) Other pins in EIA-232 are omitted in EIA-530 such as ring indicator signal
quality detector and data signal rate selector
X21
bull Is an interface standard designed by ITU-T to address many problems
existing in the EIA interfaces and at the same time paves the way for alldigital communications
bull A large proportion of the circuits in the EIA interfaces are used forcontrol since these are necessary to implement control functions as
separate signals With a separate line control information is represented
only by positive and negative voltages But if control signals are encoded
using a meaningful control characters from a system such as ASCII it can be transmitted over data lines
bull X21 eliminates most of the control circuits of the EIA standards and
instead directs its traffic over the data circuits To make this consolidationof functionality possible both the DTE and the DCE must have added
circuit logic that enables them to transform the control codes into bit
streams that can be sent over the data line Both also need additional logicto discriminate between control information and data upon receipt
bull Design of X21 allows not only to use fewer pins but also to be used in
digital telecommunications where control information is sent from deviceto device over a network rather than just between a DTE and a DCE
bull X21 is useful both as an interface to connect digital computers to analogdevices such as modems and as a connector between digital computers and
digital interfaces such as ISDN and X25
Byte Timing
bull Another advantage offered by X21 is that of timing lines to control bytesynchronization in addition to the bit synchronization provided by the EIA
standards By adding a byte timing pulse improves the overall
synchronization of transmissions
Control and indication
bull Pins 3 and 5 of the DB-15 connector are used for the initial handshake or
agreement to begin transmitting Pin 3 is the equivalent of request to send
Pin 5 is the equivalent of clear to send
MODEMbull Modem stands for modulatordemodulator
bull A modulator converts a digital to an analog signalbull A demodulator converts an analog signal to a digital signal
bull The series of 1s and 0s are transformed through the mechanism of ASK
FSK PSK and QAM
Transmission Rate
Bandwidth
bull Every line has upper limit and a lower limit on the frequencies of the
signals it carry this limited range is called the bandwidth
It handles connection establishment and termination data transfer
and packet creation protocols Two types of PLP packets information and control
Up to 4096 channels may be multiplexed at the PLP level Specifies protocols to handle resizing of messages
FRAME RELAY LAYERSbull A technology that operates only at the physical and datalink layers No protocol is
specified for the physical layer the choice is up to the user
bull Eliminates the extensive error checking necessary in X25 protocol
bull It uses simplified version of HDLC protocol in the datalink layerbull It uses routing and switching functions of the datalink layers Frames not packets
are switched
bull It uses PVCs (permanent virtual circuits) Identified through a DLCI (dalta linkconnection identifier)
bull A switch in frame relay performs error checking and routing Error correction is
left to the other protocols at the higher layers
bull Flow control is handled through setting the BECN (backwards explicit congestionnotification) and FECN (forward explicit congestion notification) in the address
field of the frame
bull
ASYNCHRONOUS TRANSFER MODE (ATM)
bull Is the cell relay protocol designed by the ATM forum and adopted by theITU-T
bull In ATM some software functions have moved to hardware this can
increase the data rate
Terms
Cell is the data packet is called a and is composed of 53 bytes (5 bytes of header and 48 bytes of payload) Because each cell is the same size and all are relatively small delay
and other problems associated with multiplexing different sized packets are avoided
A cell network is based on permanent virtual circuit (PVC) routing
bull Virtual Path Identifier (VPI) specifies the path a cell should take
1 Virtual path (VP) switching ndash channels within each VP remain with the VP
2 Virtual path and channel (VPC) switching ndash a channel from one VP may pass into
another VP
IXSDHSONET
Synchronous Optical Network (SONET)
Developed by ANSI
Synchronous Digital Hierarchy (SDH)
Developed by ITU-T
SONETSDH
The two are nearly identical ANSI and ITU-T defined standards that arefundamentally similar and ultimately compatible
Is a synchronous network a single clock is used to handle the timing of
transmissions and equipment across the entire network
SONET
It defines the hierarchy of signals called synchronous transport signals (STS)
Optical carrier (OC) levels are the implementation of STS
SONETSDH Rates
STS OC Rate (Mbps) STM
STS-1 OC-1 5184
STS-3 OC-3 15552 STM-1
STS-9 OC-9 46656 STM-3
STS-12 OC-12 62208 STM-4
STS-18 OC-18 93312 STM-6
STS-24 OC-24 124416 STM-8
STS-36 OC-36 186623 STM-12
STS-48 OC-48 248832 STM-16
STS-96 OC-96 497664 STM-32
STS-192 OC-192 995328 STM-64
STM-synchronous transport module
SONET Four Layers
1 Photonic layer is the lowest and performs physical layer activities
A frame at the photonic layer for STS-1 consists of 6480 bits (8000 framessec)
2-4 Section Line and Path layers correspond to the OSI modelrsquos datalink layer Eachof these layers is responsible for signal transfer across a specific portion of the
1 STS multiplexer combines several optical signals to make an STS signal2 Regenerator removes noise from optical signal
3 Adddrop multiplexer adds STS signals from different paths and removes STS signal
from a path
XTCPIP
Transmission Control ProtocolInternetworking Protocol (TCPIP)
Is a set of rules and procedures that governs the exchange of messages in an
internetwork Originally developed as a protocol for networks that wanted to be connected to
ARPANET a US Department of Defense project now known as Internet
Is a five-layer protocol suite whose bottom four layers match the OSI model fairly
closely The highest level the application layer corresponds to OSIrsquos top threelayers
Internet Protocol (IP) Is defined at the network layer
Unreliable and connectionless Is basically the set of rules for one network communicating with any other To be part of internet organization needs an internet network number unique
number to be included in any packet sent out of the network onto the internet
IP packet is known as datagram consists of a variable header and a variable data
field
IP Address
Uniquely defines the connection of a host to its network The host with more than
one IP address is multi-homed host
IP Addressing
32 bit binary number usually represented as 4 decimal values Equivalent to 4 octets ( 8 bits each decimal value ) Dotted decimal notation Consists of 2 parts the network and the node
Network ndash identifier of particular network on the internet
Host ndash identifier of a particular device which can be a server or a
A frame is an information unit whose source and destination are datalink layer entities A
frame is composed of the datalink layer header (and possibly a trailer) and upper-layer
data The header and the trailer contain control information intended for the data-link
layer entity in the destination system
A packet is an information unit whose source and destination are network-layer entities
A packet is composed of the network-layer header (and possibly a trailer0 and upper-layer data The header and the trailer contain control information intended for the
network-layer entity in the destination system The data from upper-layer entities is
encapsulated in the network-layer header and trailer
The term datagram usually refers to an information unit whose source and destination
are network-layer entities that use connectionless network services
The term segment usually refers to an information unit whose source and destination aretransport layer entities
A message is an information unit whose source and destination entities exist above the
network layer (often the application layer)
A cell is an information unit of a fixed size whose source and destination are datalink
layer entities Cells are used in switched environments such as ATM and SMDS A cell
is composed of the header and payload The header contains control informationintended for the destination datalink layer entity and is typically 5 bytes long The
payload contains upper-layer data that is encapsulated in the cell header and typically 48 bytes long
Data unit is a generic term that refers to a variety of information units Some commondata units are service data units (SDU) protocol data units (PDU) and bridge protocol
data units (BPDU) SDUs are information units from upper-layer protocols that define a
service request to a lower-layer protocol PDU is OSI terminology for a packet BPDUS
are used by the spanning-tree algorithm as hello messages
Three Basic elements in Layer Services
1 Service User is the OSI layer that requests services from an adjacent OSI layer
2 Service Provider is the OSI layer that provides services to service users
3 Service Access Point is a conceptual location at which one OSI layer can request the
Peer-to-peer ndash all nodes has equal authority in the networkClient-server ndash a certain node called server has full control over the network and
nodes in the network
LAN Components
1 Server
Is a computer in a network that shared by multiple users
2 Network Interface Card
A printed circuit board that plugs into a network server or client computer It
enables the computer to be physically connected to the network cable which provides the
physical layer connection among the computers in the network It performs electronicfunctions of the access method or datalink protocol
3 HubA device that acts as central connection of certain LAN topology It is capable of
regeneration and switching of signals from one node to another Also known as
concentrator multiple access unit transceiver or repeater
4 Cable
The transmission link in a network These are unshielded twisted pairs (UTP)
shielded twisted pair (STP) coaxial cable and fiber optics cable
5 Connector
The terminating end of the cable to be plug-in or connected to the device
6 Network Operating System (NOS)
The control program that resides in a server or workstation within a LAN Ithandles requests for data transfer from all the users of the networks It interact with the
application programs and the computerrsquos operating system
7 Client
It is the requesting computer from the supplying computers or server
8 Other Peripheral Devices
These are the devices attached to the network such as printers scanners and the
LAN Access Methodrarr it is unnecessary to have a MAC in pt-to-pt full duplex because there are
only two devices on the circuit and full duplex permits either device to
transmit at any time
rarr if it is point-to-point half duplex it needs MAC and also in multipoint full
duplex configurations since several devices share the same channelrarr to ensure that no two devices attempt to transmit data at the same time
1 Controlled Access
a X-on X-off
rarrthe oldest media access control protocols dating back to the days of theteletype
b Polling
rarr the process of sending signal to a terminal to transmit or asking it to receive
rarr it uses ldquoroll call pollingrdquo with scheme or sequence
Node 3its your time to transmitNode 1 its your turn to sendNode 4 you can transmit after node 1
c Token Passing
rarrA channel accessing arrangement that is best suited for ring topology witheither a baseband or broadband network It uses a token and the token circulate in
the network
Token is an electrical signal that circulate around the ring network from onestation to another If the station has the token it can send a message
2 Contention
rarr opposite of controlled access
rarr devices wait until the circuit is free and transmit whenever it has data to send
a Carrier Sense Multiple Access with Collision Detection (CSMACD)
rarrA channel accessing method a node monitors the line to determine if the line is
busy If the station has a message to transmit but the line is busy it waits for an
idle condition before it transmits its message
Collision is the situation when two nodes transmit simultaneously using one link
Backoff Time is the ceasing time before the station attempts to transmit again
Is the process where computers on a token-ring network detect a problem and
attempt to fix it
FDDI (Fiber Distributed Data Interface)
Uses fiber-optic cable and token-passing to create a very fast reliable networkoperating at speeds of 100 Mbps
It includes up to 500 nodes over a distance of 100 km It uses ring topology with two counter-rotating rings It is implement as true physical ring topology A break in a FDDI network results in packets being sent back on the second ring
1 End system (ES) is a network device that does not perform routing or other traffic
forwarding functions Typical ESs include such devices as terminals PCs and printers
2 Intermediate System (IS) is a network device that performs routing or other traffic-forwarding functions it includes devices such as routers switches and bridges
Intradomain IS communicates within a single autonomous system Interdomain IS communicates within and between autonomous systems
3 Area is a logical group of network segments and their attached devices Areas aresubdivisions of autonomous systems
4 Autonomous System (AS) is a collection of networks under a common administrationthat share a common routing strategy Autonomous system are subdivided into areas and
It involves three phases connection establishment- a single path between the
source and the destination systems is determined data transfer ndash transmitted sequentially
over the path that has been established and connection termination ndash termination of paththat has been establish
Connectionless
Offers two important advantages over connection-oriented service dynamic path
selection ndash enables traffic to be routed around network failures because paths are selectedon a packet-to-packet basis dynamic bandwidth allocation ndash used more efficiently
because network resources are not allocated a bandwidth that they will not use
Virtual Circuits
Switched Virtual CircuitA virtual circuit that is dynamically established on demand and terminated when
transmission is completed It has three phases circuit establishment data transfer and
circuit termination
Permanent Virtual Circuit
A permanently established virtual circuit consists of one mode the data transfer
Internetworking Devices
Hubs
bull A hub is a central network device that connects network devices in a startopology
bull Advanced hubs provide very high speed connectivity for FDDI Fast Ethernet
frame relay and ATM networks
bull It is also referred to as a concentrator (or switch) which is a device that can
have multiple inputs and outputs all active at a one time
bull Services offered by hubs
bull Provide a central unit from which to connect multiple nodes into one network
bull Permit large numbers of computers to be connected on single or multipleLANs
bull Reduce network congestion through centralizing network design
bull Provide multiprotocol services such as Ethernet-to-FDDI connectivity
bull Consolidate the network backbone
bull Enable high-speed communications
bull Provide connections for several different media types
bull Multiplexers are network devices that can receive multiple inputs and transmit
them to a shared network medium
bull A multiplexer is a switch that divides a communication medium into multiple
channels so several nodes can communicate at the same time
bull A signal that is multiplexed must be demultiplexed at the other endbull Multiplexers simply are switches used in old and new technology such as the
following
Telephone switching
Switching telecommunications lines to create multiple channels on a
single line Serial communications to enable more than one terminal to
communicate over a single line Fast Ethernet X25 ISDN frame relay ATM and other networking
technologies to create multiple communication channels over a single
communications cable
bull Work at the OSI physical level switching from channel to channel using one
of three physical methods
bull Time division multiplexing (TDM)
bull Frequency division multiplexing (FDM)
bull Wavelength division multiplexing (WDM)
Bridges
A bridge is a network device that connects different LAN segments using the same accessmethod
Bridges are used to
bull To extend a LAN when the maximum connections limit has been reached
bull To extend a LAN beyond the length limit
bull To segment LANs to reduce data traffic bottlenecks
bull To prevent unauthorized access to LAN (for security)
Standby indicator Pin 36 provides the confirmation signal from the DCE in response to
select standby (pin 32)
Send common Pin 37 provides a common signal return line for unbalanced circuits from
the DTE to the DCE
Electrical Specifications
bull EIA 449 uses two other standards to define its electrical specifications
RS-423 (for unbalanced circuits) and RS-422 (for balanced circuits)
RS-423 Unbalanced Mode
bull An unbalanced circuit specification meaning that it defines only one linefor propagating a signal All signals in this standard use a common return
(or ground) to complete the circuit
RS-422 Balanced Mode
bull A balanced circuit specification meaning that it defines two lines for the propagation of each signal Signals again use a common return (or ground)
for the return of the signal In balanced mode EIA-449 utilizes both pinsin each Category I but does not use the Category II pins The ratio of data
rate to distance is much higher that that of the unbalanced standard or of
EIA-232 10 Mbps for transmission of 40 feet bull In balanced mode two lines carry the same transmission it do not carry
identical signals The signal on one line is the complement of the signal
on the other When plotted the complement looks like a mirror image ofthe original signal Instead of listening to either actual signal the receiver
detects the differences between the two This mechanism makes a balanced circuit less susceptible to noise than an unbalanced circuit and
improves performance
EIA-530
bull A version of EIA-449 that uses DB-25 pins
bull The pin functions of EIA-530 are essentially the same of EIA-449
Category I plus three pins from Category II (the loopback circuits) Other pins in EIA-232 are omitted in EIA-530 such as ring indicator signal
quality detector and data signal rate selector
X21
bull Is an interface standard designed by ITU-T to address many problems
existing in the EIA interfaces and at the same time paves the way for alldigital communications
bull A large proportion of the circuits in the EIA interfaces are used forcontrol since these are necessary to implement control functions as
separate signals With a separate line control information is represented
only by positive and negative voltages But if control signals are encoded
using a meaningful control characters from a system such as ASCII it can be transmitted over data lines
bull X21 eliminates most of the control circuits of the EIA standards and
instead directs its traffic over the data circuits To make this consolidationof functionality possible both the DTE and the DCE must have added
circuit logic that enables them to transform the control codes into bit
streams that can be sent over the data line Both also need additional logicto discriminate between control information and data upon receipt
bull Design of X21 allows not only to use fewer pins but also to be used in
digital telecommunications where control information is sent from deviceto device over a network rather than just between a DTE and a DCE
bull X21 is useful both as an interface to connect digital computers to analogdevices such as modems and as a connector between digital computers and
digital interfaces such as ISDN and X25
Byte Timing
bull Another advantage offered by X21 is that of timing lines to control bytesynchronization in addition to the bit synchronization provided by the EIA
standards By adding a byte timing pulse improves the overall
synchronization of transmissions
Control and indication
bull Pins 3 and 5 of the DB-15 connector are used for the initial handshake or
agreement to begin transmitting Pin 3 is the equivalent of request to send
Pin 5 is the equivalent of clear to send
MODEMbull Modem stands for modulatordemodulator
bull A modulator converts a digital to an analog signalbull A demodulator converts an analog signal to a digital signal
bull The series of 1s and 0s are transformed through the mechanism of ASK
FSK PSK and QAM
Transmission Rate
Bandwidth
bull Every line has upper limit and a lower limit on the frequencies of the
signals it carry this limited range is called the bandwidth
It handles connection establishment and termination data transfer
and packet creation protocols Two types of PLP packets information and control
Up to 4096 channels may be multiplexed at the PLP level Specifies protocols to handle resizing of messages
FRAME RELAY LAYERSbull A technology that operates only at the physical and datalink layers No protocol is
specified for the physical layer the choice is up to the user
bull Eliminates the extensive error checking necessary in X25 protocol
bull It uses simplified version of HDLC protocol in the datalink layerbull It uses routing and switching functions of the datalink layers Frames not packets
are switched
bull It uses PVCs (permanent virtual circuits) Identified through a DLCI (dalta linkconnection identifier)
bull A switch in frame relay performs error checking and routing Error correction is
left to the other protocols at the higher layers
bull Flow control is handled through setting the BECN (backwards explicit congestionnotification) and FECN (forward explicit congestion notification) in the address
field of the frame
bull
ASYNCHRONOUS TRANSFER MODE (ATM)
bull Is the cell relay protocol designed by the ATM forum and adopted by theITU-T
bull In ATM some software functions have moved to hardware this can
increase the data rate
Terms
Cell is the data packet is called a and is composed of 53 bytes (5 bytes of header and 48 bytes of payload) Because each cell is the same size and all are relatively small delay
and other problems associated with multiplexing different sized packets are avoided
A cell network is based on permanent virtual circuit (PVC) routing
bull Virtual Path Identifier (VPI) specifies the path a cell should take
1 Virtual path (VP) switching ndash channels within each VP remain with the VP
2 Virtual path and channel (VPC) switching ndash a channel from one VP may pass into
another VP
IXSDHSONET
Synchronous Optical Network (SONET)
Developed by ANSI
Synchronous Digital Hierarchy (SDH)
Developed by ITU-T
SONETSDH
The two are nearly identical ANSI and ITU-T defined standards that arefundamentally similar and ultimately compatible
Is a synchronous network a single clock is used to handle the timing of
transmissions and equipment across the entire network
SONET
It defines the hierarchy of signals called synchronous transport signals (STS)
Optical carrier (OC) levels are the implementation of STS
SONETSDH Rates
STS OC Rate (Mbps) STM
STS-1 OC-1 5184
STS-3 OC-3 15552 STM-1
STS-9 OC-9 46656 STM-3
STS-12 OC-12 62208 STM-4
STS-18 OC-18 93312 STM-6
STS-24 OC-24 124416 STM-8
STS-36 OC-36 186623 STM-12
STS-48 OC-48 248832 STM-16
STS-96 OC-96 497664 STM-32
STS-192 OC-192 995328 STM-64
STM-synchronous transport module
SONET Four Layers
1 Photonic layer is the lowest and performs physical layer activities
A frame at the photonic layer for STS-1 consists of 6480 bits (8000 framessec)
2-4 Section Line and Path layers correspond to the OSI modelrsquos datalink layer Eachof these layers is responsible for signal transfer across a specific portion of the
1 STS multiplexer combines several optical signals to make an STS signal2 Regenerator removes noise from optical signal
3 Adddrop multiplexer adds STS signals from different paths and removes STS signal
from a path
XTCPIP
Transmission Control ProtocolInternetworking Protocol (TCPIP)
Is a set of rules and procedures that governs the exchange of messages in an
internetwork Originally developed as a protocol for networks that wanted to be connected to
ARPANET a US Department of Defense project now known as Internet
Is a five-layer protocol suite whose bottom four layers match the OSI model fairly
closely The highest level the application layer corresponds to OSIrsquos top threelayers
Internet Protocol (IP) Is defined at the network layer
Unreliable and connectionless Is basically the set of rules for one network communicating with any other To be part of internet organization needs an internet network number unique
number to be included in any packet sent out of the network onto the internet
IP packet is known as datagram consists of a variable header and a variable data
field
IP Address
Uniquely defines the connection of a host to its network The host with more than
one IP address is multi-homed host
IP Addressing
32 bit binary number usually represented as 4 decimal values Equivalent to 4 octets ( 8 bits each decimal value ) Dotted decimal notation Consists of 2 parts the network and the node
Network ndash identifier of particular network on the internet
Host ndash identifier of a particular device which can be a server or a
A frame is an information unit whose source and destination are datalink layer entities A
frame is composed of the datalink layer header (and possibly a trailer) and upper-layer
data The header and the trailer contain control information intended for the data-link
layer entity in the destination system
A packet is an information unit whose source and destination are network-layer entities
A packet is composed of the network-layer header (and possibly a trailer0 and upper-layer data The header and the trailer contain control information intended for the
network-layer entity in the destination system The data from upper-layer entities is
encapsulated in the network-layer header and trailer
The term datagram usually refers to an information unit whose source and destination
are network-layer entities that use connectionless network services
The term segment usually refers to an information unit whose source and destination aretransport layer entities
A message is an information unit whose source and destination entities exist above the
network layer (often the application layer)
A cell is an information unit of a fixed size whose source and destination are datalink
layer entities Cells are used in switched environments such as ATM and SMDS A cell
is composed of the header and payload The header contains control informationintended for the destination datalink layer entity and is typically 5 bytes long The
payload contains upper-layer data that is encapsulated in the cell header and typically 48 bytes long
Data unit is a generic term that refers to a variety of information units Some commondata units are service data units (SDU) protocol data units (PDU) and bridge protocol
data units (BPDU) SDUs are information units from upper-layer protocols that define a
service request to a lower-layer protocol PDU is OSI terminology for a packet BPDUS
are used by the spanning-tree algorithm as hello messages
Three Basic elements in Layer Services
1 Service User is the OSI layer that requests services from an adjacent OSI layer
2 Service Provider is the OSI layer that provides services to service users
3 Service Access Point is a conceptual location at which one OSI layer can request the
Peer-to-peer ndash all nodes has equal authority in the networkClient-server ndash a certain node called server has full control over the network and
nodes in the network
LAN Components
1 Server
Is a computer in a network that shared by multiple users
2 Network Interface Card
A printed circuit board that plugs into a network server or client computer It
enables the computer to be physically connected to the network cable which provides the
physical layer connection among the computers in the network It performs electronicfunctions of the access method or datalink protocol
3 HubA device that acts as central connection of certain LAN topology It is capable of
regeneration and switching of signals from one node to another Also known as
concentrator multiple access unit transceiver or repeater
4 Cable
The transmission link in a network These are unshielded twisted pairs (UTP)
shielded twisted pair (STP) coaxial cable and fiber optics cable
5 Connector
The terminating end of the cable to be plug-in or connected to the device
6 Network Operating System (NOS)
The control program that resides in a server or workstation within a LAN Ithandles requests for data transfer from all the users of the networks It interact with the
application programs and the computerrsquos operating system
7 Client
It is the requesting computer from the supplying computers or server
8 Other Peripheral Devices
These are the devices attached to the network such as printers scanners and the
LAN Access Methodrarr it is unnecessary to have a MAC in pt-to-pt full duplex because there are
only two devices on the circuit and full duplex permits either device to
transmit at any time
rarr if it is point-to-point half duplex it needs MAC and also in multipoint full
duplex configurations since several devices share the same channelrarr to ensure that no two devices attempt to transmit data at the same time
1 Controlled Access
a X-on X-off
rarrthe oldest media access control protocols dating back to the days of theteletype
b Polling
rarr the process of sending signal to a terminal to transmit or asking it to receive
rarr it uses ldquoroll call pollingrdquo with scheme or sequence
Node 3its your time to transmitNode 1 its your turn to sendNode 4 you can transmit after node 1
c Token Passing
rarrA channel accessing arrangement that is best suited for ring topology witheither a baseband or broadband network It uses a token and the token circulate in
the network
Token is an electrical signal that circulate around the ring network from onestation to another If the station has the token it can send a message
2 Contention
rarr opposite of controlled access
rarr devices wait until the circuit is free and transmit whenever it has data to send
a Carrier Sense Multiple Access with Collision Detection (CSMACD)
rarrA channel accessing method a node monitors the line to determine if the line is
busy If the station has a message to transmit but the line is busy it waits for an
idle condition before it transmits its message
Collision is the situation when two nodes transmit simultaneously using one link
Backoff Time is the ceasing time before the station attempts to transmit again
Is the process where computers on a token-ring network detect a problem and
attempt to fix it
FDDI (Fiber Distributed Data Interface)
Uses fiber-optic cable and token-passing to create a very fast reliable networkoperating at speeds of 100 Mbps
It includes up to 500 nodes over a distance of 100 km It uses ring topology with two counter-rotating rings It is implement as true physical ring topology A break in a FDDI network results in packets being sent back on the second ring
1 End system (ES) is a network device that does not perform routing or other traffic
forwarding functions Typical ESs include such devices as terminals PCs and printers
2 Intermediate System (IS) is a network device that performs routing or other traffic-forwarding functions it includes devices such as routers switches and bridges
Intradomain IS communicates within a single autonomous system Interdomain IS communicates within and between autonomous systems
3 Area is a logical group of network segments and their attached devices Areas aresubdivisions of autonomous systems
4 Autonomous System (AS) is a collection of networks under a common administrationthat share a common routing strategy Autonomous system are subdivided into areas and
It involves three phases connection establishment- a single path between the
source and the destination systems is determined data transfer ndash transmitted sequentially
over the path that has been established and connection termination ndash termination of paththat has been establish
Connectionless
Offers two important advantages over connection-oriented service dynamic path
selection ndash enables traffic to be routed around network failures because paths are selectedon a packet-to-packet basis dynamic bandwidth allocation ndash used more efficiently
because network resources are not allocated a bandwidth that they will not use
Virtual Circuits
Switched Virtual CircuitA virtual circuit that is dynamically established on demand and terminated when
transmission is completed It has three phases circuit establishment data transfer and
circuit termination
Permanent Virtual Circuit
A permanently established virtual circuit consists of one mode the data transfer
Internetworking Devices
Hubs
bull A hub is a central network device that connects network devices in a startopology
bull Advanced hubs provide very high speed connectivity for FDDI Fast Ethernet
frame relay and ATM networks
bull It is also referred to as a concentrator (or switch) which is a device that can
have multiple inputs and outputs all active at a one time
bull Services offered by hubs
bull Provide a central unit from which to connect multiple nodes into one network
bull Permit large numbers of computers to be connected on single or multipleLANs
bull Reduce network congestion through centralizing network design
bull Provide multiprotocol services such as Ethernet-to-FDDI connectivity
bull Consolidate the network backbone
bull Enable high-speed communications
bull Provide connections for several different media types
bull Multiplexers are network devices that can receive multiple inputs and transmit
them to a shared network medium
bull A multiplexer is a switch that divides a communication medium into multiple
channels so several nodes can communicate at the same time
bull A signal that is multiplexed must be demultiplexed at the other endbull Multiplexers simply are switches used in old and new technology such as the
following
Telephone switching
Switching telecommunications lines to create multiple channels on a
single line Serial communications to enable more than one terminal to
communicate over a single line Fast Ethernet X25 ISDN frame relay ATM and other networking
technologies to create multiple communication channels over a single
communications cable
bull Work at the OSI physical level switching from channel to channel using one
of three physical methods
bull Time division multiplexing (TDM)
bull Frequency division multiplexing (FDM)
bull Wavelength division multiplexing (WDM)
Bridges
A bridge is a network device that connects different LAN segments using the same accessmethod
Bridges are used to
bull To extend a LAN when the maximum connections limit has been reached
bull To extend a LAN beyond the length limit
bull To segment LANs to reduce data traffic bottlenecks
bull To prevent unauthorized access to LAN (for security)
Standby indicator Pin 36 provides the confirmation signal from the DCE in response to
select standby (pin 32)
Send common Pin 37 provides a common signal return line for unbalanced circuits from
the DTE to the DCE
Electrical Specifications
bull EIA 449 uses two other standards to define its electrical specifications
RS-423 (for unbalanced circuits) and RS-422 (for balanced circuits)
RS-423 Unbalanced Mode
bull An unbalanced circuit specification meaning that it defines only one linefor propagating a signal All signals in this standard use a common return
(or ground) to complete the circuit
RS-422 Balanced Mode
bull A balanced circuit specification meaning that it defines two lines for the propagation of each signal Signals again use a common return (or ground)
for the return of the signal In balanced mode EIA-449 utilizes both pinsin each Category I but does not use the Category II pins The ratio of data
rate to distance is much higher that that of the unbalanced standard or of
EIA-232 10 Mbps for transmission of 40 feet bull In balanced mode two lines carry the same transmission it do not carry
identical signals The signal on one line is the complement of the signal
on the other When plotted the complement looks like a mirror image ofthe original signal Instead of listening to either actual signal the receiver
detects the differences between the two This mechanism makes a balanced circuit less susceptible to noise than an unbalanced circuit and
improves performance
EIA-530
bull A version of EIA-449 that uses DB-25 pins
bull The pin functions of EIA-530 are essentially the same of EIA-449
Category I plus three pins from Category II (the loopback circuits) Other pins in EIA-232 are omitted in EIA-530 such as ring indicator signal
quality detector and data signal rate selector
X21
bull Is an interface standard designed by ITU-T to address many problems
existing in the EIA interfaces and at the same time paves the way for alldigital communications
bull A large proportion of the circuits in the EIA interfaces are used forcontrol since these are necessary to implement control functions as
separate signals With a separate line control information is represented
only by positive and negative voltages But if control signals are encoded
using a meaningful control characters from a system such as ASCII it can be transmitted over data lines
bull X21 eliminates most of the control circuits of the EIA standards and
instead directs its traffic over the data circuits To make this consolidationof functionality possible both the DTE and the DCE must have added
circuit logic that enables them to transform the control codes into bit
streams that can be sent over the data line Both also need additional logicto discriminate between control information and data upon receipt
bull Design of X21 allows not only to use fewer pins but also to be used in
digital telecommunications where control information is sent from deviceto device over a network rather than just between a DTE and a DCE
bull X21 is useful both as an interface to connect digital computers to analogdevices such as modems and as a connector between digital computers and
digital interfaces such as ISDN and X25
Byte Timing
bull Another advantage offered by X21 is that of timing lines to control bytesynchronization in addition to the bit synchronization provided by the EIA
standards By adding a byte timing pulse improves the overall
synchronization of transmissions
Control and indication
bull Pins 3 and 5 of the DB-15 connector are used for the initial handshake or
agreement to begin transmitting Pin 3 is the equivalent of request to send
Pin 5 is the equivalent of clear to send
MODEMbull Modem stands for modulatordemodulator
bull A modulator converts a digital to an analog signalbull A demodulator converts an analog signal to a digital signal
bull The series of 1s and 0s are transformed through the mechanism of ASK
FSK PSK and QAM
Transmission Rate
Bandwidth
bull Every line has upper limit and a lower limit on the frequencies of the
signals it carry this limited range is called the bandwidth
It handles connection establishment and termination data transfer
and packet creation protocols Two types of PLP packets information and control
Up to 4096 channels may be multiplexed at the PLP level Specifies protocols to handle resizing of messages
FRAME RELAY LAYERSbull A technology that operates only at the physical and datalink layers No protocol is
specified for the physical layer the choice is up to the user
bull Eliminates the extensive error checking necessary in X25 protocol
bull It uses simplified version of HDLC protocol in the datalink layerbull It uses routing and switching functions of the datalink layers Frames not packets
are switched
bull It uses PVCs (permanent virtual circuits) Identified through a DLCI (dalta linkconnection identifier)
bull A switch in frame relay performs error checking and routing Error correction is
left to the other protocols at the higher layers
bull Flow control is handled through setting the BECN (backwards explicit congestionnotification) and FECN (forward explicit congestion notification) in the address
field of the frame
bull
ASYNCHRONOUS TRANSFER MODE (ATM)
bull Is the cell relay protocol designed by the ATM forum and adopted by theITU-T
bull In ATM some software functions have moved to hardware this can
increase the data rate
Terms
Cell is the data packet is called a and is composed of 53 bytes (5 bytes of header and 48 bytes of payload) Because each cell is the same size and all are relatively small delay
and other problems associated with multiplexing different sized packets are avoided
A cell network is based on permanent virtual circuit (PVC) routing
bull Virtual Path Identifier (VPI) specifies the path a cell should take
1 Virtual path (VP) switching ndash channels within each VP remain with the VP
2 Virtual path and channel (VPC) switching ndash a channel from one VP may pass into
another VP
IXSDHSONET
Synchronous Optical Network (SONET)
Developed by ANSI
Synchronous Digital Hierarchy (SDH)
Developed by ITU-T
SONETSDH
The two are nearly identical ANSI and ITU-T defined standards that arefundamentally similar and ultimately compatible
Is a synchronous network a single clock is used to handle the timing of
transmissions and equipment across the entire network
SONET
It defines the hierarchy of signals called synchronous transport signals (STS)
Optical carrier (OC) levels are the implementation of STS
SONETSDH Rates
STS OC Rate (Mbps) STM
STS-1 OC-1 5184
STS-3 OC-3 15552 STM-1
STS-9 OC-9 46656 STM-3
STS-12 OC-12 62208 STM-4
STS-18 OC-18 93312 STM-6
STS-24 OC-24 124416 STM-8
STS-36 OC-36 186623 STM-12
STS-48 OC-48 248832 STM-16
STS-96 OC-96 497664 STM-32
STS-192 OC-192 995328 STM-64
STM-synchronous transport module
SONET Four Layers
1 Photonic layer is the lowest and performs physical layer activities
A frame at the photonic layer for STS-1 consists of 6480 bits (8000 framessec)
2-4 Section Line and Path layers correspond to the OSI modelrsquos datalink layer Eachof these layers is responsible for signal transfer across a specific portion of the
1 STS multiplexer combines several optical signals to make an STS signal2 Regenerator removes noise from optical signal
3 Adddrop multiplexer adds STS signals from different paths and removes STS signal
from a path
XTCPIP
Transmission Control ProtocolInternetworking Protocol (TCPIP)
Is a set of rules and procedures that governs the exchange of messages in an
internetwork Originally developed as a protocol for networks that wanted to be connected to
ARPANET a US Department of Defense project now known as Internet
Is a five-layer protocol suite whose bottom four layers match the OSI model fairly
closely The highest level the application layer corresponds to OSIrsquos top threelayers
Internet Protocol (IP) Is defined at the network layer
Unreliable and connectionless Is basically the set of rules for one network communicating with any other To be part of internet organization needs an internet network number unique
number to be included in any packet sent out of the network onto the internet
IP packet is known as datagram consists of a variable header and a variable data
field
IP Address
Uniquely defines the connection of a host to its network The host with more than
one IP address is multi-homed host
IP Addressing
32 bit binary number usually represented as 4 decimal values Equivalent to 4 octets ( 8 bits each decimal value ) Dotted decimal notation Consists of 2 parts the network and the node
Network ndash identifier of particular network on the internet
Host ndash identifier of a particular device which can be a server or a
Peer-to-peer ndash all nodes has equal authority in the networkClient-server ndash a certain node called server has full control over the network and
nodes in the network
LAN Components
1 Server
Is a computer in a network that shared by multiple users
2 Network Interface Card
A printed circuit board that plugs into a network server or client computer It
enables the computer to be physically connected to the network cable which provides the
physical layer connection among the computers in the network It performs electronicfunctions of the access method or datalink protocol
3 HubA device that acts as central connection of certain LAN topology It is capable of
regeneration and switching of signals from one node to another Also known as
concentrator multiple access unit transceiver or repeater
4 Cable
The transmission link in a network These are unshielded twisted pairs (UTP)
shielded twisted pair (STP) coaxial cable and fiber optics cable
5 Connector
The terminating end of the cable to be plug-in or connected to the device
6 Network Operating System (NOS)
The control program that resides in a server or workstation within a LAN Ithandles requests for data transfer from all the users of the networks It interact with the
application programs and the computerrsquos operating system
7 Client
It is the requesting computer from the supplying computers or server
8 Other Peripheral Devices
These are the devices attached to the network such as printers scanners and the
LAN Access Methodrarr it is unnecessary to have a MAC in pt-to-pt full duplex because there are
only two devices on the circuit and full duplex permits either device to
transmit at any time
rarr if it is point-to-point half duplex it needs MAC and also in multipoint full
duplex configurations since several devices share the same channelrarr to ensure that no two devices attempt to transmit data at the same time
1 Controlled Access
a X-on X-off
rarrthe oldest media access control protocols dating back to the days of theteletype
b Polling
rarr the process of sending signal to a terminal to transmit or asking it to receive
rarr it uses ldquoroll call pollingrdquo with scheme or sequence
Node 3its your time to transmitNode 1 its your turn to sendNode 4 you can transmit after node 1
c Token Passing
rarrA channel accessing arrangement that is best suited for ring topology witheither a baseband or broadband network It uses a token and the token circulate in
the network
Token is an electrical signal that circulate around the ring network from onestation to another If the station has the token it can send a message
2 Contention
rarr opposite of controlled access
rarr devices wait until the circuit is free and transmit whenever it has data to send
a Carrier Sense Multiple Access with Collision Detection (CSMACD)
rarrA channel accessing method a node monitors the line to determine if the line is
busy If the station has a message to transmit but the line is busy it waits for an
idle condition before it transmits its message
Collision is the situation when two nodes transmit simultaneously using one link
Backoff Time is the ceasing time before the station attempts to transmit again
Is the process where computers on a token-ring network detect a problem and
attempt to fix it
FDDI (Fiber Distributed Data Interface)
Uses fiber-optic cable and token-passing to create a very fast reliable networkoperating at speeds of 100 Mbps
It includes up to 500 nodes over a distance of 100 km It uses ring topology with two counter-rotating rings It is implement as true physical ring topology A break in a FDDI network results in packets being sent back on the second ring
1 End system (ES) is a network device that does not perform routing or other traffic
forwarding functions Typical ESs include such devices as terminals PCs and printers
2 Intermediate System (IS) is a network device that performs routing or other traffic-forwarding functions it includes devices such as routers switches and bridges
Intradomain IS communicates within a single autonomous system Interdomain IS communicates within and between autonomous systems
3 Area is a logical group of network segments and their attached devices Areas aresubdivisions of autonomous systems
4 Autonomous System (AS) is a collection of networks under a common administrationthat share a common routing strategy Autonomous system are subdivided into areas and
It involves three phases connection establishment- a single path between the
source and the destination systems is determined data transfer ndash transmitted sequentially
over the path that has been established and connection termination ndash termination of paththat has been establish
Connectionless
Offers two important advantages over connection-oriented service dynamic path
selection ndash enables traffic to be routed around network failures because paths are selectedon a packet-to-packet basis dynamic bandwidth allocation ndash used more efficiently
because network resources are not allocated a bandwidth that they will not use
Virtual Circuits
Switched Virtual CircuitA virtual circuit that is dynamically established on demand and terminated when
transmission is completed It has three phases circuit establishment data transfer and
circuit termination
Permanent Virtual Circuit
A permanently established virtual circuit consists of one mode the data transfer
Internetworking Devices
Hubs
bull A hub is a central network device that connects network devices in a startopology
bull Advanced hubs provide very high speed connectivity for FDDI Fast Ethernet
frame relay and ATM networks
bull It is also referred to as a concentrator (or switch) which is a device that can
have multiple inputs and outputs all active at a one time
bull Services offered by hubs
bull Provide a central unit from which to connect multiple nodes into one network
bull Permit large numbers of computers to be connected on single or multipleLANs
bull Reduce network congestion through centralizing network design
bull Provide multiprotocol services such as Ethernet-to-FDDI connectivity
bull Consolidate the network backbone
bull Enable high-speed communications
bull Provide connections for several different media types
bull Multiplexers are network devices that can receive multiple inputs and transmit
them to a shared network medium
bull A multiplexer is a switch that divides a communication medium into multiple
channels so several nodes can communicate at the same time
bull A signal that is multiplexed must be demultiplexed at the other endbull Multiplexers simply are switches used in old and new technology such as the
following
Telephone switching
Switching telecommunications lines to create multiple channels on a
single line Serial communications to enable more than one terminal to
communicate over a single line Fast Ethernet X25 ISDN frame relay ATM and other networking
technologies to create multiple communication channels over a single
communications cable
bull Work at the OSI physical level switching from channel to channel using one
of three physical methods
bull Time division multiplexing (TDM)
bull Frequency division multiplexing (FDM)
bull Wavelength division multiplexing (WDM)
Bridges
A bridge is a network device that connects different LAN segments using the same accessmethod
Bridges are used to
bull To extend a LAN when the maximum connections limit has been reached
bull To extend a LAN beyond the length limit
bull To segment LANs to reduce data traffic bottlenecks
bull To prevent unauthorized access to LAN (for security)
Standby indicator Pin 36 provides the confirmation signal from the DCE in response to
select standby (pin 32)
Send common Pin 37 provides a common signal return line for unbalanced circuits from
the DTE to the DCE
Electrical Specifications
bull EIA 449 uses two other standards to define its electrical specifications
RS-423 (for unbalanced circuits) and RS-422 (for balanced circuits)
RS-423 Unbalanced Mode
bull An unbalanced circuit specification meaning that it defines only one linefor propagating a signal All signals in this standard use a common return
(or ground) to complete the circuit
RS-422 Balanced Mode
bull A balanced circuit specification meaning that it defines two lines for the propagation of each signal Signals again use a common return (or ground)
for the return of the signal In balanced mode EIA-449 utilizes both pinsin each Category I but does not use the Category II pins The ratio of data
rate to distance is much higher that that of the unbalanced standard or of
EIA-232 10 Mbps for transmission of 40 feet bull In balanced mode two lines carry the same transmission it do not carry
identical signals The signal on one line is the complement of the signal
on the other When plotted the complement looks like a mirror image ofthe original signal Instead of listening to either actual signal the receiver
detects the differences between the two This mechanism makes a balanced circuit less susceptible to noise than an unbalanced circuit and
improves performance
EIA-530
bull A version of EIA-449 that uses DB-25 pins
bull The pin functions of EIA-530 are essentially the same of EIA-449
Category I plus three pins from Category II (the loopback circuits) Other pins in EIA-232 are omitted in EIA-530 such as ring indicator signal
quality detector and data signal rate selector
X21
bull Is an interface standard designed by ITU-T to address many problems
existing in the EIA interfaces and at the same time paves the way for alldigital communications
bull A large proportion of the circuits in the EIA interfaces are used forcontrol since these are necessary to implement control functions as
separate signals With a separate line control information is represented
only by positive and negative voltages But if control signals are encoded
using a meaningful control characters from a system such as ASCII it can be transmitted over data lines
bull X21 eliminates most of the control circuits of the EIA standards and
instead directs its traffic over the data circuits To make this consolidationof functionality possible both the DTE and the DCE must have added
circuit logic that enables them to transform the control codes into bit
streams that can be sent over the data line Both also need additional logicto discriminate between control information and data upon receipt
bull Design of X21 allows not only to use fewer pins but also to be used in
digital telecommunications where control information is sent from deviceto device over a network rather than just between a DTE and a DCE
bull X21 is useful both as an interface to connect digital computers to analogdevices such as modems and as a connector between digital computers and
digital interfaces such as ISDN and X25
Byte Timing
bull Another advantage offered by X21 is that of timing lines to control bytesynchronization in addition to the bit synchronization provided by the EIA
standards By adding a byte timing pulse improves the overall
synchronization of transmissions
Control and indication
bull Pins 3 and 5 of the DB-15 connector are used for the initial handshake or
agreement to begin transmitting Pin 3 is the equivalent of request to send
Pin 5 is the equivalent of clear to send
MODEMbull Modem stands for modulatordemodulator
bull A modulator converts a digital to an analog signalbull A demodulator converts an analog signal to a digital signal
bull The series of 1s and 0s are transformed through the mechanism of ASK
FSK PSK and QAM
Transmission Rate
Bandwidth
bull Every line has upper limit and a lower limit on the frequencies of the
signals it carry this limited range is called the bandwidth
It handles connection establishment and termination data transfer
and packet creation protocols Two types of PLP packets information and control
Up to 4096 channels may be multiplexed at the PLP level Specifies protocols to handle resizing of messages
FRAME RELAY LAYERSbull A technology that operates only at the physical and datalink layers No protocol is
specified for the physical layer the choice is up to the user
bull Eliminates the extensive error checking necessary in X25 protocol
bull It uses simplified version of HDLC protocol in the datalink layerbull It uses routing and switching functions of the datalink layers Frames not packets
are switched
bull It uses PVCs (permanent virtual circuits) Identified through a DLCI (dalta linkconnection identifier)
bull A switch in frame relay performs error checking and routing Error correction is
left to the other protocols at the higher layers
bull Flow control is handled through setting the BECN (backwards explicit congestionnotification) and FECN (forward explicit congestion notification) in the address
field of the frame
bull
ASYNCHRONOUS TRANSFER MODE (ATM)
bull Is the cell relay protocol designed by the ATM forum and adopted by theITU-T
bull In ATM some software functions have moved to hardware this can
increase the data rate
Terms
Cell is the data packet is called a and is composed of 53 bytes (5 bytes of header and 48 bytes of payload) Because each cell is the same size and all are relatively small delay
and other problems associated with multiplexing different sized packets are avoided
A cell network is based on permanent virtual circuit (PVC) routing
bull Virtual Path Identifier (VPI) specifies the path a cell should take
1 Virtual path (VP) switching ndash channels within each VP remain with the VP
2 Virtual path and channel (VPC) switching ndash a channel from one VP may pass into
another VP
IXSDHSONET
Synchronous Optical Network (SONET)
Developed by ANSI
Synchronous Digital Hierarchy (SDH)
Developed by ITU-T
SONETSDH
The two are nearly identical ANSI and ITU-T defined standards that arefundamentally similar and ultimately compatible
Is a synchronous network a single clock is used to handle the timing of
transmissions and equipment across the entire network
SONET
It defines the hierarchy of signals called synchronous transport signals (STS)
Optical carrier (OC) levels are the implementation of STS
SONETSDH Rates
STS OC Rate (Mbps) STM
STS-1 OC-1 5184
STS-3 OC-3 15552 STM-1
STS-9 OC-9 46656 STM-3
STS-12 OC-12 62208 STM-4
STS-18 OC-18 93312 STM-6
STS-24 OC-24 124416 STM-8
STS-36 OC-36 186623 STM-12
STS-48 OC-48 248832 STM-16
STS-96 OC-96 497664 STM-32
STS-192 OC-192 995328 STM-64
STM-synchronous transport module
SONET Four Layers
1 Photonic layer is the lowest and performs physical layer activities
A frame at the photonic layer for STS-1 consists of 6480 bits (8000 framessec)
2-4 Section Line and Path layers correspond to the OSI modelrsquos datalink layer Eachof these layers is responsible for signal transfer across a specific portion of the
1 STS multiplexer combines several optical signals to make an STS signal2 Regenerator removes noise from optical signal
3 Adddrop multiplexer adds STS signals from different paths and removes STS signal
from a path
XTCPIP
Transmission Control ProtocolInternetworking Protocol (TCPIP)
Is a set of rules and procedures that governs the exchange of messages in an
internetwork Originally developed as a protocol for networks that wanted to be connected to
ARPANET a US Department of Defense project now known as Internet
Is a five-layer protocol suite whose bottom four layers match the OSI model fairly
closely The highest level the application layer corresponds to OSIrsquos top threelayers
Internet Protocol (IP) Is defined at the network layer
Unreliable and connectionless Is basically the set of rules for one network communicating with any other To be part of internet organization needs an internet network number unique
number to be included in any packet sent out of the network onto the internet
IP packet is known as datagram consists of a variable header and a variable data
field
IP Address
Uniquely defines the connection of a host to its network The host with more than
one IP address is multi-homed host
IP Addressing
32 bit binary number usually represented as 4 decimal values Equivalent to 4 octets ( 8 bits each decimal value ) Dotted decimal notation Consists of 2 parts the network and the node
Network ndash identifier of particular network on the internet
Host ndash identifier of a particular device which can be a server or a
Peer-to-peer ndash all nodes has equal authority in the networkClient-server ndash a certain node called server has full control over the network and
nodes in the network
LAN Components
1 Server
Is a computer in a network that shared by multiple users
2 Network Interface Card
A printed circuit board that plugs into a network server or client computer It
enables the computer to be physically connected to the network cable which provides the
physical layer connection among the computers in the network It performs electronicfunctions of the access method or datalink protocol
3 HubA device that acts as central connection of certain LAN topology It is capable of
regeneration and switching of signals from one node to another Also known as
concentrator multiple access unit transceiver or repeater
4 Cable
The transmission link in a network These are unshielded twisted pairs (UTP)
shielded twisted pair (STP) coaxial cable and fiber optics cable
5 Connector
The terminating end of the cable to be plug-in or connected to the device
6 Network Operating System (NOS)
The control program that resides in a server or workstation within a LAN Ithandles requests for data transfer from all the users of the networks It interact with the
application programs and the computerrsquos operating system
7 Client
It is the requesting computer from the supplying computers or server
8 Other Peripheral Devices
These are the devices attached to the network such as printers scanners and the
LAN Access Methodrarr it is unnecessary to have a MAC in pt-to-pt full duplex because there are
only two devices on the circuit and full duplex permits either device to
transmit at any time
rarr if it is point-to-point half duplex it needs MAC and also in multipoint full
duplex configurations since several devices share the same channelrarr to ensure that no two devices attempt to transmit data at the same time
1 Controlled Access
a X-on X-off
rarrthe oldest media access control protocols dating back to the days of theteletype
b Polling
rarr the process of sending signal to a terminal to transmit or asking it to receive
rarr it uses ldquoroll call pollingrdquo with scheme or sequence
Node 3its your time to transmitNode 1 its your turn to sendNode 4 you can transmit after node 1
c Token Passing
rarrA channel accessing arrangement that is best suited for ring topology witheither a baseband or broadband network It uses a token and the token circulate in
the network
Token is an electrical signal that circulate around the ring network from onestation to another If the station has the token it can send a message
2 Contention
rarr opposite of controlled access
rarr devices wait until the circuit is free and transmit whenever it has data to send
a Carrier Sense Multiple Access with Collision Detection (CSMACD)
rarrA channel accessing method a node monitors the line to determine if the line is
busy If the station has a message to transmit but the line is busy it waits for an
idle condition before it transmits its message
Collision is the situation when two nodes transmit simultaneously using one link
Backoff Time is the ceasing time before the station attempts to transmit again
Is the process where computers on a token-ring network detect a problem and
attempt to fix it
FDDI (Fiber Distributed Data Interface)
Uses fiber-optic cable and token-passing to create a very fast reliable networkoperating at speeds of 100 Mbps
It includes up to 500 nodes over a distance of 100 km It uses ring topology with two counter-rotating rings It is implement as true physical ring topology A break in a FDDI network results in packets being sent back on the second ring
1 End system (ES) is a network device that does not perform routing or other traffic
forwarding functions Typical ESs include such devices as terminals PCs and printers
2 Intermediate System (IS) is a network device that performs routing or other traffic-forwarding functions it includes devices such as routers switches and bridges
Intradomain IS communicates within a single autonomous system Interdomain IS communicates within and between autonomous systems
3 Area is a logical group of network segments and their attached devices Areas aresubdivisions of autonomous systems
4 Autonomous System (AS) is a collection of networks under a common administrationthat share a common routing strategy Autonomous system are subdivided into areas and
It involves three phases connection establishment- a single path between the
source and the destination systems is determined data transfer ndash transmitted sequentially
over the path that has been established and connection termination ndash termination of paththat has been establish
Connectionless
Offers two important advantages over connection-oriented service dynamic path
selection ndash enables traffic to be routed around network failures because paths are selectedon a packet-to-packet basis dynamic bandwidth allocation ndash used more efficiently
because network resources are not allocated a bandwidth that they will not use
Virtual Circuits
Switched Virtual CircuitA virtual circuit that is dynamically established on demand and terminated when
transmission is completed It has three phases circuit establishment data transfer and
circuit termination
Permanent Virtual Circuit
A permanently established virtual circuit consists of one mode the data transfer
Internetworking Devices
Hubs
bull A hub is a central network device that connects network devices in a startopology
bull Advanced hubs provide very high speed connectivity for FDDI Fast Ethernet
frame relay and ATM networks
bull It is also referred to as a concentrator (or switch) which is a device that can
have multiple inputs and outputs all active at a one time
bull Services offered by hubs
bull Provide a central unit from which to connect multiple nodes into one network
bull Permit large numbers of computers to be connected on single or multipleLANs
bull Reduce network congestion through centralizing network design
bull Provide multiprotocol services such as Ethernet-to-FDDI connectivity
bull Consolidate the network backbone
bull Enable high-speed communications
bull Provide connections for several different media types
bull Multiplexers are network devices that can receive multiple inputs and transmit
them to a shared network medium
bull A multiplexer is a switch that divides a communication medium into multiple
channels so several nodes can communicate at the same time
bull A signal that is multiplexed must be demultiplexed at the other endbull Multiplexers simply are switches used in old and new technology such as the
following
Telephone switching
Switching telecommunications lines to create multiple channels on a
single line Serial communications to enable more than one terminal to
communicate over a single line Fast Ethernet X25 ISDN frame relay ATM and other networking
technologies to create multiple communication channels over a single
communications cable
bull Work at the OSI physical level switching from channel to channel using one
of three physical methods
bull Time division multiplexing (TDM)
bull Frequency division multiplexing (FDM)
bull Wavelength division multiplexing (WDM)
Bridges
A bridge is a network device that connects different LAN segments using the same accessmethod
Bridges are used to
bull To extend a LAN when the maximum connections limit has been reached
bull To extend a LAN beyond the length limit
bull To segment LANs to reduce data traffic bottlenecks
bull To prevent unauthorized access to LAN (for security)
Standby indicator Pin 36 provides the confirmation signal from the DCE in response to
select standby (pin 32)
Send common Pin 37 provides a common signal return line for unbalanced circuits from
the DTE to the DCE
Electrical Specifications
bull EIA 449 uses two other standards to define its electrical specifications
RS-423 (for unbalanced circuits) and RS-422 (for balanced circuits)
RS-423 Unbalanced Mode
bull An unbalanced circuit specification meaning that it defines only one linefor propagating a signal All signals in this standard use a common return
(or ground) to complete the circuit
RS-422 Balanced Mode
bull A balanced circuit specification meaning that it defines two lines for the propagation of each signal Signals again use a common return (or ground)
for the return of the signal In balanced mode EIA-449 utilizes both pinsin each Category I but does not use the Category II pins The ratio of data
rate to distance is much higher that that of the unbalanced standard or of
EIA-232 10 Mbps for transmission of 40 feet bull In balanced mode two lines carry the same transmission it do not carry
identical signals The signal on one line is the complement of the signal
on the other When plotted the complement looks like a mirror image ofthe original signal Instead of listening to either actual signal the receiver
detects the differences between the two This mechanism makes a balanced circuit less susceptible to noise than an unbalanced circuit and
improves performance
EIA-530
bull A version of EIA-449 that uses DB-25 pins
bull The pin functions of EIA-530 are essentially the same of EIA-449
Category I plus three pins from Category II (the loopback circuits) Other pins in EIA-232 are omitted in EIA-530 such as ring indicator signal
quality detector and data signal rate selector
X21
bull Is an interface standard designed by ITU-T to address many problems
existing in the EIA interfaces and at the same time paves the way for alldigital communications
bull A large proportion of the circuits in the EIA interfaces are used forcontrol since these are necessary to implement control functions as
separate signals With a separate line control information is represented
only by positive and negative voltages But if control signals are encoded
using a meaningful control characters from a system such as ASCII it can be transmitted over data lines
bull X21 eliminates most of the control circuits of the EIA standards and
instead directs its traffic over the data circuits To make this consolidationof functionality possible both the DTE and the DCE must have added
circuit logic that enables them to transform the control codes into bit
streams that can be sent over the data line Both also need additional logicto discriminate between control information and data upon receipt
bull Design of X21 allows not only to use fewer pins but also to be used in
digital telecommunications where control information is sent from deviceto device over a network rather than just between a DTE and a DCE
bull X21 is useful both as an interface to connect digital computers to analogdevices such as modems and as a connector between digital computers and
digital interfaces such as ISDN and X25
Byte Timing
bull Another advantage offered by X21 is that of timing lines to control bytesynchronization in addition to the bit synchronization provided by the EIA
standards By adding a byte timing pulse improves the overall
synchronization of transmissions
Control and indication
bull Pins 3 and 5 of the DB-15 connector are used for the initial handshake or
agreement to begin transmitting Pin 3 is the equivalent of request to send
Pin 5 is the equivalent of clear to send
MODEMbull Modem stands for modulatordemodulator
bull A modulator converts a digital to an analog signalbull A demodulator converts an analog signal to a digital signal
bull The series of 1s and 0s are transformed through the mechanism of ASK
FSK PSK and QAM
Transmission Rate
Bandwidth
bull Every line has upper limit and a lower limit on the frequencies of the
signals it carry this limited range is called the bandwidth
It handles connection establishment and termination data transfer
and packet creation protocols Two types of PLP packets information and control
Up to 4096 channels may be multiplexed at the PLP level Specifies protocols to handle resizing of messages
FRAME RELAY LAYERSbull A technology that operates only at the physical and datalink layers No protocol is
specified for the physical layer the choice is up to the user
bull Eliminates the extensive error checking necessary in X25 protocol
bull It uses simplified version of HDLC protocol in the datalink layerbull It uses routing and switching functions of the datalink layers Frames not packets
are switched
bull It uses PVCs (permanent virtual circuits) Identified through a DLCI (dalta linkconnection identifier)
bull A switch in frame relay performs error checking and routing Error correction is
left to the other protocols at the higher layers
bull Flow control is handled through setting the BECN (backwards explicit congestionnotification) and FECN (forward explicit congestion notification) in the address
field of the frame
bull
ASYNCHRONOUS TRANSFER MODE (ATM)
bull Is the cell relay protocol designed by the ATM forum and adopted by theITU-T
bull In ATM some software functions have moved to hardware this can
increase the data rate
Terms
Cell is the data packet is called a and is composed of 53 bytes (5 bytes of header and 48 bytes of payload) Because each cell is the same size and all are relatively small delay
and other problems associated with multiplexing different sized packets are avoided
A cell network is based on permanent virtual circuit (PVC) routing
bull Virtual Path Identifier (VPI) specifies the path a cell should take
1 Virtual path (VP) switching ndash channels within each VP remain with the VP
2 Virtual path and channel (VPC) switching ndash a channel from one VP may pass into
another VP
IXSDHSONET
Synchronous Optical Network (SONET)
Developed by ANSI
Synchronous Digital Hierarchy (SDH)
Developed by ITU-T
SONETSDH
The two are nearly identical ANSI and ITU-T defined standards that arefundamentally similar and ultimately compatible
Is a synchronous network a single clock is used to handle the timing of
transmissions and equipment across the entire network
SONET
It defines the hierarchy of signals called synchronous transport signals (STS)
Optical carrier (OC) levels are the implementation of STS
SONETSDH Rates
STS OC Rate (Mbps) STM
STS-1 OC-1 5184
STS-3 OC-3 15552 STM-1
STS-9 OC-9 46656 STM-3
STS-12 OC-12 62208 STM-4
STS-18 OC-18 93312 STM-6
STS-24 OC-24 124416 STM-8
STS-36 OC-36 186623 STM-12
STS-48 OC-48 248832 STM-16
STS-96 OC-96 497664 STM-32
STS-192 OC-192 995328 STM-64
STM-synchronous transport module
SONET Four Layers
1 Photonic layer is the lowest and performs physical layer activities
A frame at the photonic layer for STS-1 consists of 6480 bits (8000 framessec)
2-4 Section Line and Path layers correspond to the OSI modelrsquos datalink layer Eachof these layers is responsible for signal transfer across a specific portion of the
1 STS multiplexer combines several optical signals to make an STS signal2 Regenerator removes noise from optical signal
3 Adddrop multiplexer adds STS signals from different paths and removes STS signal
from a path
XTCPIP
Transmission Control ProtocolInternetworking Protocol (TCPIP)
Is a set of rules and procedures that governs the exchange of messages in an
internetwork Originally developed as a protocol for networks that wanted to be connected to
ARPANET a US Department of Defense project now known as Internet
Is a five-layer protocol suite whose bottom four layers match the OSI model fairly
closely The highest level the application layer corresponds to OSIrsquos top threelayers
Internet Protocol (IP) Is defined at the network layer
Unreliable and connectionless Is basically the set of rules for one network communicating with any other To be part of internet organization needs an internet network number unique
number to be included in any packet sent out of the network onto the internet
IP packet is known as datagram consists of a variable header and a variable data
field
IP Address
Uniquely defines the connection of a host to its network The host with more than
one IP address is multi-homed host
IP Addressing
32 bit binary number usually represented as 4 decimal values Equivalent to 4 octets ( 8 bits each decimal value ) Dotted decimal notation Consists of 2 parts the network and the node
Network ndash identifier of particular network on the internet
Host ndash identifier of a particular device which can be a server or a
Peer-to-peer ndash all nodes has equal authority in the networkClient-server ndash a certain node called server has full control over the network and
nodes in the network
LAN Components
1 Server
Is a computer in a network that shared by multiple users
2 Network Interface Card
A printed circuit board that plugs into a network server or client computer It
enables the computer to be physically connected to the network cable which provides the
physical layer connection among the computers in the network It performs electronicfunctions of the access method or datalink protocol
3 HubA device that acts as central connection of certain LAN topology It is capable of
regeneration and switching of signals from one node to another Also known as
concentrator multiple access unit transceiver or repeater
4 Cable
The transmission link in a network These are unshielded twisted pairs (UTP)
shielded twisted pair (STP) coaxial cable and fiber optics cable
5 Connector
The terminating end of the cable to be plug-in or connected to the device
6 Network Operating System (NOS)
The control program that resides in a server or workstation within a LAN Ithandles requests for data transfer from all the users of the networks It interact with the
application programs and the computerrsquos operating system
7 Client
It is the requesting computer from the supplying computers or server
8 Other Peripheral Devices
These are the devices attached to the network such as printers scanners and the
LAN Access Methodrarr it is unnecessary to have a MAC in pt-to-pt full duplex because there are
only two devices on the circuit and full duplex permits either device to
transmit at any time
rarr if it is point-to-point half duplex it needs MAC and also in multipoint full
duplex configurations since several devices share the same channelrarr to ensure that no two devices attempt to transmit data at the same time
1 Controlled Access
a X-on X-off
rarrthe oldest media access control protocols dating back to the days of theteletype
b Polling
rarr the process of sending signal to a terminal to transmit or asking it to receive
rarr it uses ldquoroll call pollingrdquo with scheme or sequence
Node 3its your time to transmitNode 1 its your turn to sendNode 4 you can transmit after node 1
c Token Passing
rarrA channel accessing arrangement that is best suited for ring topology witheither a baseband or broadband network It uses a token and the token circulate in
the network
Token is an electrical signal that circulate around the ring network from onestation to another If the station has the token it can send a message
2 Contention
rarr opposite of controlled access
rarr devices wait until the circuit is free and transmit whenever it has data to send
a Carrier Sense Multiple Access with Collision Detection (CSMACD)
rarrA channel accessing method a node monitors the line to determine if the line is
busy If the station has a message to transmit but the line is busy it waits for an
idle condition before it transmits its message
Collision is the situation when two nodes transmit simultaneously using one link
Backoff Time is the ceasing time before the station attempts to transmit again
Is the process where computers on a token-ring network detect a problem and
attempt to fix it
FDDI (Fiber Distributed Data Interface)
Uses fiber-optic cable and token-passing to create a very fast reliable networkoperating at speeds of 100 Mbps
It includes up to 500 nodes over a distance of 100 km It uses ring topology with two counter-rotating rings It is implement as true physical ring topology A break in a FDDI network results in packets being sent back on the second ring
1 End system (ES) is a network device that does not perform routing or other traffic
forwarding functions Typical ESs include such devices as terminals PCs and printers
2 Intermediate System (IS) is a network device that performs routing or other traffic-forwarding functions it includes devices such as routers switches and bridges
Intradomain IS communicates within a single autonomous system Interdomain IS communicates within and between autonomous systems
3 Area is a logical group of network segments and their attached devices Areas aresubdivisions of autonomous systems
4 Autonomous System (AS) is a collection of networks under a common administrationthat share a common routing strategy Autonomous system are subdivided into areas and
It involves three phases connection establishment- a single path between the
source and the destination systems is determined data transfer ndash transmitted sequentially
over the path that has been established and connection termination ndash termination of paththat has been establish
Connectionless
Offers two important advantages over connection-oriented service dynamic path
selection ndash enables traffic to be routed around network failures because paths are selectedon a packet-to-packet basis dynamic bandwidth allocation ndash used more efficiently
because network resources are not allocated a bandwidth that they will not use
Virtual Circuits
Switched Virtual CircuitA virtual circuit that is dynamically established on demand and terminated when
transmission is completed It has three phases circuit establishment data transfer and
circuit termination
Permanent Virtual Circuit
A permanently established virtual circuit consists of one mode the data transfer
Internetworking Devices
Hubs
bull A hub is a central network device that connects network devices in a startopology
bull Advanced hubs provide very high speed connectivity for FDDI Fast Ethernet
frame relay and ATM networks
bull It is also referred to as a concentrator (or switch) which is a device that can
have multiple inputs and outputs all active at a one time
bull Services offered by hubs
bull Provide a central unit from which to connect multiple nodes into one network
bull Permit large numbers of computers to be connected on single or multipleLANs
bull Reduce network congestion through centralizing network design
bull Provide multiprotocol services such as Ethernet-to-FDDI connectivity
bull Consolidate the network backbone
bull Enable high-speed communications
bull Provide connections for several different media types
bull Multiplexers are network devices that can receive multiple inputs and transmit
them to a shared network medium
bull A multiplexer is a switch that divides a communication medium into multiple
channels so several nodes can communicate at the same time
bull A signal that is multiplexed must be demultiplexed at the other endbull Multiplexers simply are switches used in old and new technology such as the
following
Telephone switching
Switching telecommunications lines to create multiple channels on a
single line Serial communications to enable more than one terminal to
communicate over a single line Fast Ethernet X25 ISDN frame relay ATM and other networking
technologies to create multiple communication channels over a single
communications cable
bull Work at the OSI physical level switching from channel to channel using one
of three physical methods
bull Time division multiplexing (TDM)
bull Frequency division multiplexing (FDM)
bull Wavelength division multiplexing (WDM)
Bridges
A bridge is a network device that connects different LAN segments using the same accessmethod
Bridges are used to
bull To extend a LAN when the maximum connections limit has been reached
bull To extend a LAN beyond the length limit
bull To segment LANs to reduce data traffic bottlenecks
bull To prevent unauthorized access to LAN (for security)
Standby indicator Pin 36 provides the confirmation signal from the DCE in response to
select standby (pin 32)
Send common Pin 37 provides a common signal return line for unbalanced circuits from
the DTE to the DCE
Electrical Specifications
bull EIA 449 uses two other standards to define its electrical specifications
RS-423 (for unbalanced circuits) and RS-422 (for balanced circuits)
RS-423 Unbalanced Mode
bull An unbalanced circuit specification meaning that it defines only one linefor propagating a signal All signals in this standard use a common return
(or ground) to complete the circuit
RS-422 Balanced Mode
bull A balanced circuit specification meaning that it defines two lines for the propagation of each signal Signals again use a common return (or ground)
for the return of the signal In balanced mode EIA-449 utilizes both pinsin each Category I but does not use the Category II pins The ratio of data
rate to distance is much higher that that of the unbalanced standard or of
EIA-232 10 Mbps for transmission of 40 feet bull In balanced mode two lines carry the same transmission it do not carry
identical signals The signal on one line is the complement of the signal
on the other When plotted the complement looks like a mirror image ofthe original signal Instead of listening to either actual signal the receiver
detects the differences between the two This mechanism makes a balanced circuit less susceptible to noise than an unbalanced circuit and
improves performance
EIA-530
bull A version of EIA-449 that uses DB-25 pins
bull The pin functions of EIA-530 are essentially the same of EIA-449
Category I plus three pins from Category II (the loopback circuits) Other pins in EIA-232 are omitted in EIA-530 such as ring indicator signal
quality detector and data signal rate selector
X21
bull Is an interface standard designed by ITU-T to address many problems
existing in the EIA interfaces and at the same time paves the way for alldigital communications
bull A large proportion of the circuits in the EIA interfaces are used forcontrol since these are necessary to implement control functions as
separate signals With a separate line control information is represented
only by positive and negative voltages But if control signals are encoded
using a meaningful control characters from a system such as ASCII it can be transmitted over data lines
bull X21 eliminates most of the control circuits of the EIA standards and
instead directs its traffic over the data circuits To make this consolidationof functionality possible both the DTE and the DCE must have added
circuit logic that enables them to transform the control codes into bit
streams that can be sent over the data line Both also need additional logicto discriminate between control information and data upon receipt
bull Design of X21 allows not only to use fewer pins but also to be used in
digital telecommunications where control information is sent from deviceto device over a network rather than just between a DTE and a DCE
bull X21 is useful both as an interface to connect digital computers to analogdevices such as modems and as a connector between digital computers and
digital interfaces such as ISDN and X25
Byte Timing
bull Another advantage offered by X21 is that of timing lines to control bytesynchronization in addition to the bit synchronization provided by the EIA
standards By adding a byte timing pulse improves the overall
synchronization of transmissions
Control and indication
bull Pins 3 and 5 of the DB-15 connector are used for the initial handshake or
agreement to begin transmitting Pin 3 is the equivalent of request to send
Pin 5 is the equivalent of clear to send
MODEMbull Modem stands for modulatordemodulator
bull A modulator converts a digital to an analog signalbull A demodulator converts an analog signal to a digital signal
bull The series of 1s and 0s are transformed through the mechanism of ASK
FSK PSK and QAM
Transmission Rate
Bandwidth
bull Every line has upper limit and a lower limit on the frequencies of the
signals it carry this limited range is called the bandwidth
It handles connection establishment and termination data transfer
and packet creation protocols Two types of PLP packets information and control
Up to 4096 channels may be multiplexed at the PLP level Specifies protocols to handle resizing of messages
FRAME RELAY LAYERSbull A technology that operates only at the physical and datalink layers No protocol is
specified for the physical layer the choice is up to the user
bull Eliminates the extensive error checking necessary in X25 protocol
bull It uses simplified version of HDLC protocol in the datalink layerbull It uses routing and switching functions of the datalink layers Frames not packets
are switched
bull It uses PVCs (permanent virtual circuits) Identified through a DLCI (dalta linkconnection identifier)
bull A switch in frame relay performs error checking and routing Error correction is
left to the other protocols at the higher layers
bull Flow control is handled through setting the BECN (backwards explicit congestionnotification) and FECN (forward explicit congestion notification) in the address
field of the frame
bull
ASYNCHRONOUS TRANSFER MODE (ATM)
bull Is the cell relay protocol designed by the ATM forum and adopted by theITU-T
bull In ATM some software functions have moved to hardware this can
increase the data rate
Terms
Cell is the data packet is called a and is composed of 53 bytes (5 bytes of header and 48 bytes of payload) Because each cell is the same size and all are relatively small delay
and other problems associated with multiplexing different sized packets are avoided
A cell network is based on permanent virtual circuit (PVC) routing
bull Virtual Path Identifier (VPI) specifies the path a cell should take
1 Virtual path (VP) switching ndash channels within each VP remain with the VP
2 Virtual path and channel (VPC) switching ndash a channel from one VP may pass into
another VP
IXSDHSONET
Synchronous Optical Network (SONET)
Developed by ANSI
Synchronous Digital Hierarchy (SDH)
Developed by ITU-T
SONETSDH
The two are nearly identical ANSI and ITU-T defined standards that arefundamentally similar and ultimately compatible
Is a synchronous network a single clock is used to handle the timing of
transmissions and equipment across the entire network
SONET
It defines the hierarchy of signals called synchronous transport signals (STS)
Optical carrier (OC) levels are the implementation of STS
SONETSDH Rates
STS OC Rate (Mbps) STM
STS-1 OC-1 5184
STS-3 OC-3 15552 STM-1
STS-9 OC-9 46656 STM-3
STS-12 OC-12 62208 STM-4
STS-18 OC-18 93312 STM-6
STS-24 OC-24 124416 STM-8
STS-36 OC-36 186623 STM-12
STS-48 OC-48 248832 STM-16
STS-96 OC-96 497664 STM-32
STS-192 OC-192 995328 STM-64
STM-synchronous transport module
SONET Four Layers
1 Photonic layer is the lowest and performs physical layer activities
A frame at the photonic layer for STS-1 consists of 6480 bits (8000 framessec)
2-4 Section Line and Path layers correspond to the OSI modelrsquos datalink layer Eachof these layers is responsible for signal transfer across a specific portion of the
1 STS multiplexer combines several optical signals to make an STS signal2 Regenerator removes noise from optical signal
3 Adddrop multiplexer adds STS signals from different paths and removes STS signal
from a path
XTCPIP
Transmission Control ProtocolInternetworking Protocol (TCPIP)
Is a set of rules and procedures that governs the exchange of messages in an
internetwork Originally developed as a protocol for networks that wanted to be connected to
ARPANET a US Department of Defense project now known as Internet
Is a five-layer protocol suite whose bottom four layers match the OSI model fairly
closely The highest level the application layer corresponds to OSIrsquos top threelayers
Internet Protocol (IP) Is defined at the network layer
Unreliable and connectionless Is basically the set of rules for one network communicating with any other To be part of internet organization needs an internet network number unique
number to be included in any packet sent out of the network onto the internet
IP packet is known as datagram consists of a variable header and a variable data
field
IP Address
Uniquely defines the connection of a host to its network The host with more than
one IP address is multi-homed host
IP Addressing
32 bit binary number usually represented as 4 decimal values Equivalent to 4 octets ( 8 bits each decimal value ) Dotted decimal notation Consists of 2 parts the network and the node
Network ndash identifier of particular network on the internet
Host ndash identifier of a particular device which can be a server or a
Peer-to-peer ndash all nodes has equal authority in the networkClient-server ndash a certain node called server has full control over the network and
nodes in the network
LAN Components
1 Server
Is a computer in a network that shared by multiple users
2 Network Interface Card
A printed circuit board that plugs into a network server or client computer It
enables the computer to be physically connected to the network cable which provides the
physical layer connection among the computers in the network It performs electronicfunctions of the access method or datalink protocol
3 HubA device that acts as central connection of certain LAN topology It is capable of
regeneration and switching of signals from one node to another Also known as
concentrator multiple access unit transceiver or repeater
4 Cable
The transmission link in a network These are unshielded twisted pairs (UTP)
shielded twisted pair (STP) coaxial cable and fiber optics cable
5 Connector
The terminating end of the cable to be plug-in or connected to the device
6 Network Operating System (NOS)
The control program that resides in a server or workstation within a LAN Ithandles requests for data transfer from all the users of the networks It interact with the
application programs and the computerrsquos operating system
7 Client
It is the requesting computer from the supplying computers or server
8 Other Peripheral Devices
These are the devices attached to the network such as printers scanners and the
LAN Access Methodrarr it is unnecessary to have a MAC in pt-to-pt full duplex because there are
only two devices on the circuit and full duplex permits either device to
transmit at any time
rarr if it is point-to-point half duplex it needs MAC and also in multipoint full
duplex configurations since several devices share the same channelrarr to ensure that no two devices attempt to transmit data at the same time
1 Controlled Access
a X-on X-off
rarrthe oldest media access control protocols dating back to the days of theteletype
b Polling
rarr the process of sending signal to a terminal to transmit or asking it to receive
rarr it uses ldquoroll call pollingrdquo with scheme or sequence
Node 3its your time to transmitNode 1 its your turn to sendNode 4 you can transmit after node 1
c Token Passing
rarrA channel accessing arrangement that is best suited for ring topology witheither a baseband or broadband network It uses a token and the token circulate in
the network
Token is an electrical signal that circulate around the ring network from onestation to another If the station has the token it can send a message
2 Contention
rarr opposite of controlled access
rarr devices wait until the circuit is free and transmit whenever it has data to send
a Carrier Sense Multiple Access with Collision Detection (CSMACD)
rarrA channel accessing method a node monitors the line to determine if the line is
busy If the station has a message to transmit but the line is busy it waits for an
idle condition before it transmits its message
Collision is the situation when two nodes transmit simultaneously using one link
Backoff Time is the ceasing time before the station attempts to transmit again
Is the process where computers on a token-ring network detect a problem and
attempt to fix it
FDDI (Fiber Distributed Data Interface)
Uses fiber-optic cable and token-passing to create a very fast reliable networkoperating at speeds of 100 Mbps
It includes up to 500 nodes over a distance of 100 km It uses ring topology with two counter-rotating rings It is implement as true physical ring topology A break in a FDDI network results in packets being sent back on the second ring
1 End system (ES) is a network device that does not perform routing or other traffic
forwarding functions Typical ESs include such devices as terminals PCs and printers
2 Intermediate System (IS) is a network device that performs routing or other traffic-forwarding functions it includes devices such as routers switches and bridges
Intradomain IS communicates within a single autonomous system Interdomain IS communicates within and between autonomous systems
3 Area is a logical group of network segments and their attached devices Areas aresubdivisions of autonomous systems
4 Autonomous System (AS) is a collection of networks under a common administrationthat share a common routing strategy Autonomous system are subdivided into areas and
It involves three phases connection establishment- a single path between the
source and the destination systems is determined data transfer ndash transmitted sequentially
over the path that has been established and connection termination ndash termination of paththat has been establish
Connectionless
Offers two important advantages over connection-oriented service dynamic path
selection ndash enables traffic to be routed around network failures because paths are selectedon a packet-to-packet basis dynamic bandwidth allocation ndash used more efficiently
because network resources are not allocated a bandwidth that they will not use
Virtual Circuits
Switched Virtual CircuitA virtual circuit that is dynamically established on demand and terminated when
transmission is completed It has three phases circuit establishment data transfer and
circuit termination
Permanent Virtual Circuit
A permanently established virtual circuit consists of one mode the data transfer
Internetworking Devices
Hubs
bull A hub is a central network device that connects network devices in a startopology
bull Advanced hubs provide very high speed connectivity for FDDI Fast Ethernet
frame relay and ATM networks
bull It is also referred to as a concentrator (or switch) which is a device that can
have multiple inputs and outputs all active at a one time
bull Services offered by hubs
bull Provide a central unit from which to connect multiple nodes into one network
bull Permit large numbers of computers to be connected on single or multipleLANs
bull Reduce network congestion through centralizing network design
bull Provide multiprotocol services such as Ethernet-to-FDDI connectivity
bull Consolidate the network backbone
bull Enable high-speed communications
bull Provide connections for several different media types
bull Multiplexers are network devices that can receive multiple inputs and transmit
them to a shared network medium
bull A multiplexer is a switch that divides a communication medium into multiple
channels so several nodes can communicate at the same time
bull A signal that is multiplexed must be demultiplexed at the other endbull Multiplexers simply are switches used in old and new technology such as the
following
Telephone switching
Switching telecommunications lines to create multiple channels on a
single line Serial communications to enable more than one terminal to
communicate over a single line Fast Ethernet X25 ISDN frame relay ATM and other networking
technologies to create multiple communication channels over a single
communications cable
bull Work at the OSI physical level switching from channel to channel using one
of three physical methods
bull Time division multiplexing (TDM)
bull Frequency division multiplexing (FDM)
bull Wavelength division multiplexing (WDM)
Bridges
A bridge is a network device that connects different LAN segments using the same accessmethod
Bridges are used to
bull To extend a LAN when the maximum connections limit has been reached
bull To extend a LAN beyond the length limit
bull To segment LANs to reduce data traffic bottlenecks
bull To prevent unauthorized access to LAN (for security)
Standby indicator Pin 36 provides the confirmation signal from the DCE in response to
select standby (pin 32)
Send common Pin 37 provides a common signal return line for unbalanced circuits from
the DTE to the DCE
Electrical Specifications
bull EIA 449 uses two other standards to define its electrical specifications
RS-423 (for unbalanced circuits) and RS-422 (for balanced circuits)
RS-423 Unbalanced Mode
bull An unbalanced circuit specification meaning that it defines only one linefor propagating a signal All signals in this standard use a common return
(or ground) to complete the circuit
RS-422 Balanced Mode
bull A balanced circuit specification meaning that it defines two lines for the propagation of each signal Signals again use a common return (or ground)
for the return of the signal In balanced mode EIA-449 utilizes both pinsin each Category I but does not use the Category II pins The ratio of data
rate to distance is much higher that that of the unbalanced standard or of
EIA-232 10 Mbps for transmission of 40 feet bull In balanced mode two lines carry the same transmission it do not carry
identical signals The signal on one line is the complement of the signal
on the other When plotted the complement looks like a mirror image ofthe original signal Instead of listening to either actual signal the receiver
detects the differences between the two This mechanism makes a balanced circuit less susceptible to noise than an unbalanced circuit and
improves performance
EIA-530
bull A version of EIA-449 that uses DB-25 pins
bull The pin functions of EIA-530 are essentially the same of EIA-449
Category I plus three pins from Category II (the loopback circuits) Other pins in EIA-232 are omitted in EIA-530 such as ring indicator signal
quality detector and data signal rate selector
X21
bull Is an interface standard designed by ITU-T to address many problems
existing in the EIA interfaces and at the same time paves the way for alldigital communications
bull A large proportion of the circuits in the EIA interfaces are used forcontrol since these are necessary to implement control functions as
separate signals With a separate line control information is represented
only by positive and negative voltages But if control signals are encoded
using a meaningful control characters from a system such as ASCII it can be transmitted over data lines
bull X21 eliminates most of the control circuits of the EIA standards and
instead directs its traffic over the data circuits To make this consolidationof functionality possible both the DTE and the DCE must have added
circuit logic that enables them to transform the control codes into bit
streams that can be sent over the data line Both also need additional logicto discriminate between control information and data upon receipt
bull Design of X21 allows not only to use fewer pins but also to be used in
digital telecommunications where control information is sent from deviceto device over a network rather than just between a DTE and a DCE
bull X21 is useful both as an interface to connect digital computers to analogdevices such as modems and as a connector between digital computers and
digital interfaces such as ISDN and X25
Byte Timing
bull Another advantage offered by X21 is that of timing lines to control bytesynchronization in addition to the bit synchronization provided by the EIA
standards By adding a byte timing pulse improves the overall
synchronization of transmissions
Control and indication
bull Pins 3 and 5 of the DB-15 connector are used for the initial handshake or
agreement to begin transmitting Pin 3 is the equivalent of request to send
Pin 5 is the equivalent of clear to send
MODEMbull Modem stands for modulatordemodulator
bull A modulator converts a digital to an analog signalbull A demodulator converts an analog signal to a digital signal
bull The series of 1s and 0s are transformed through the mechanism of ASK
FSK PSK and QAM
Transmission Rate
Bandwidth
bull Every line has upper limit and a lower limit on the frequencies of the
signals it carry this limited range is called the bandwidth
It handles connection establishment and termination data transfer
and packet creation protocols Two types of PLP packets information and control
Up to 4096 channels may be multiplexed at the PLP level Specifies protocols to handle resizing of messages
FRAME RELAY LAYERSbull A technology that operates only at the physical and datalink layers No protocol is
specified for the physical layer the choice is up to the user
bull Eliminates the extensive error checking necessary in X25 protocol
bull It uses simplified version of HDLC protocol in the datalink layerbull It uses routing and switching functions of the datalink layers Frames not packets
are switched
bull It uses PVCs (permanent virtual circuits) Identified through a DLCI (dalta linkconnection identifier)
bull A switch in frame relay performs error checking and routing Error correction is
left to the other protocols at the higher layers
bull Flow control is handled through setting the BECN (backwards explicit congestionnotification) and FECN (forward explicit congestion notification) in the address
field of the frame
bull
ASYNCHRONOUS TRANSFER MODE (ATM)
bull Is the cell relay protocol designed by the ATM forum and adopted by theITU-T
bull In ATM some software functions have moved to hardware this can
increase the data rate
Terms
Cell is the data packet is called a and is composed of 53 bytes (5 bytes of header and 48 bytes of payload) Because each cell is the same size and all are relatively small delay
and other problems associated with multiplexing different sized packets are avoided
A cell network is based on permanent virtual circuit (PVC) routing
bull Virtual Path Identifier (VPI) specifies the path a cell should take
1 Virtual path (VP) switching ndash channels within each VP remain with the VP
2 Virtual path and channel (VPC) switching ndash a channel from one VP may pass into
another VP
IXSDHSONET
Synchronous Optical Network (SONET)
Developed by ANSI
Synchronous Digital Hierarchy (SDH)
Developed by ITU-T
SONETSDH
The two are nearly identical ANSI and ITU-T defined standards that arefundamentally similar and ultimately compatible
Is a synchronous network a single clock is used to handle the timing of
transmissions and equipment across the entire network
SONET
It defines the hierarchy of signals called synchronous transport signals (STS)
Optical carrier (OC) levels are the implementation of STS
SONETSDH Rates
STS OC Rate (Mbps) STM
STS-1 OC-1 5184
STS-3 OC-3 15552 STM-1
STS-9 OC-9 46656 STM-3
STS-12 OC-12 62208 STM-4
STS-18 OC-18 93312 STM-6
STS-24 OC-24 124416 STM-8
STS-36 OC-36 186623 STM-12
STS-48 OC-48 248832 STM-16
STS-96 OC-96 497664 STM-32
STS-192 OC-192 995328 STM-64
STM-synchronous transport module
SONET Four Layers
1 Photonic layer is the lowest and performs physical layer activities
A frame at the photonic layer for STS-1 consists of 6480 bits (8000 framessec)
2-4 Section Line and Path layers correspond to the OSI modelrsquos datalink layer Eachof these layers is responsible for signal transfer across a specific portion of the
1 STS multiplexer combines several optical signals to make an STS signal2 Regenerator removes noise from optical signal
3 Adddrop multiplexer adds STS signals from different paths and removes STS signal
from a path
XTCPIP
Transmission Control ProtocolInternetworking Protocol (TCPIP)
Is a set of rules and procedures that governs the exchange of messages in an
internetwork Originally developed as a protocol for networks that wanted to be connected to
ARPANET a US Department of Defense project now known as Internet
Is a five-layer protocol suite whose bottom four layers match the OSI model fairly
closely The highest level the application layer corresponds to OSIrsquos top threelayers
Internet Protocol (IP) Is defined at the network layer
Unreliable and connectionless Is basically the set of rules for one network communicating with any other To be part of internet organization needs an internet network number unique
number to be included in any packet sent out of the network onto the internet
IP packet is known as datagram consists of a variable header and a variable data
field
IP Address
Uniquely defines the connection of a host to its network The host with more than
one IP address is multi-homed host
IP Addressing
32 bit binary number usually represented as 4 decimal values Equivalent to 4 octets ( 8 bits each decimal value ) Dotted decimal notation Consists of 2 parts the network and the node
Network ndash identifier of particular network on the internet
Host ndash identifier of a particular device which can be a server or a
Peer-to-peer ndash all nodes has equal authority in the networkClient-server ndash a certain node called server has full control over the network and
nodes in the network
LAN Components
1 Server
Is a computer in a network that shared by multiple users
2 Network Interface Card
A printed circuit board that plugs into a network server or client computer It
enables the computer to be physically connected to the network cable which provides the
physical layer connection among the computers in the network It performs electronicfunctions of the access method or datalink protocol
3 HubA device that acts as central connection of certain LAN topology It is capable of
regeneration and switching of signals from one node to another Also known as
concentrator multiple access unit transceiver or repeater
4 Cable
The transmission link in a network These are unshielded twisted pairs (UTP)
shielded twisted pair (STP) coaxial cable and fiber optics cable
5 Connector
The terminating end of the cable to be plug-in or connected to the device
6 Network Operating System (NOS)
The control program that resides in a server or workstation within a LAN Ithandles requests for data transfer from all the users of the networks It interact with the
application programs and the computerrsquos operating system
7 Client
It is the requesting computer from the supplying computers or server
8 Other Peripheral Devices
These are the devices attached to the network such as printers scanners and the
LAN Access Methodrarr it is unnecessary to have a MAC in pt-to-pt full duplex because there are
only two devices on the circuit and full duplex permits either device to
transmit at any time
rarr if it is point-to-point half duplex it needs MAC and also in multipoint full
duplex configurations since several devices share the same channelrarr to ensure that no two devices attempt to transmit data at the same time
1 Controlled Access
a X-on X-off
rarrthe oldest media access control protocols dating back to the days of theteletype
b Polling
rarr the process of sending signal to a terminal to transmit or asking it to receive
rarr it uses ldquoroll call pollingrdquo with scheme or sequence
Node 3its your time to transmitNode 1 its your turn to sendNode 4 you can transmit after node 1
c Token Passing
rarrA channel accessing arrangement that is best suited for ring topology witheither a baseband or broadband network It uses a token and the token circulate in
the network
Token is an electrical signal that circulate around the ring network from onestation to another If the station has the token it can send a message
2 Contention
rarr opposite of controlled access
rarr devices wait until the circuit is free and transmit whenever it has data to send
a Carrier Sense Multiple Access with Collision Detection (CSMACD)
rarrA channel accessing method a node monitors the line to determine if the line is
busy If the station has a message to transmit but the line is busy it waits for an
idle condition before it transmits its message
Collision is the situation when two nodes transmit simultaneously using one link
Backoff Time is the ceasing time before the station attempts to transmit again
Is the process where computers on a token-ring network detect a problem and
attempt to fix it
FDDI (Fiber Distributed Data Interface)
Uses fiber-optic cable and token-passing to create a very fast reliable networkoperating at speeds of 100 Mbps
It includes up to 500 nodes over a distance of 100 km It uses ring topology with two counter-rotating rings It is implement as true physical ring topology A break in a FDDI network results in packets being sent back on the second ring
1 End system (ES) is a network device that does not perform routing or other traffic
forwarding functions Typical ESs include such devices as terminals PCs and printers
2 Intermediate System (IS) is a network device that performs routing or other traffic-forwarding functions it includes devices such as routers switches and bridges
Intradomain IS communicates within a single autonomous system Interdomain IS communicates within and between autonomous systems
3 Area is a logical group of network segments and their attached devices Areas aresubdivisions of autonomous systems
4 Autonomous System (AS) is a collection of networks under a common administrationthat share a common routing strategy Autonomous system are subdivided into areas and
It involves three phases connection establishment- a single path between the
source and the destination systems is determined data transfer ndash transmitted sequentially
over the path that has been established and connection termination ndash termination of paththat has been establish
Connectionless
Offers two important advantages over connection-oriented service dynamic path
selection ndash enables traffic to be routed around network failures because paths are selectedon a packet-to-packet basis dynamic bandwidth allocation ndash used more efficiently
because network resources are not allocated a bandwidth that they will not use
Virtual Circuits
Switched Virtual CircuitA virtual circuit that is dynamically established on demand and terminated when
transmission is completed It has three phases circuit establishment data transfer and
circuit termination
Permanent Virtual Circuit
A permanently established virtual circuit consists of one mode the data transfer
Internetworking Devices
Hubs
bull A hub is a central network device that connects network devices in a startopology
bull Advanced hubs provide very high speed connectivity for FDDI Fast Ethernet
frame relay and ATM networks
bull It is also referred to as a concentrator (or switch) which is a device that can
have multiple inputs and outputs all active at a one time
bull Services offered by hubs
bull Provide a central unit from which to connect multiple nodes into one network
bull Permit large numbers of computers to be connected on single or multipleLANs
bull Reduce network congestion through centralizing network design
bull Provide multiprotocol services such as Ethernet-to-FDDI connectivity
bull Consolidate the network backbone
bull Enable high-speed communications
bull Provide connections for several different media types
bull Multiplexers are network devices that can receive multiple inputs and transmit
them to a shared network medium
bull A multiplexer is a switch that divides a communication medium into multiple
channels so several nodes can communicate at the same time
bull A signal that is multiplexed must be demultiplexed at the other endbull Multiplexers simply are switches used in old and new technology such as the
following
Telephone switching
Switching telecommunications lines to create multiple channels on a
single line Serial communications to enable more than one terminal to
communicate over a single line Fast Ethernet X25 ISDN frame relay ATM and other networking
technologies to create multiple communication channels over a single
communications cable
bull Work at the OSI physical level switching from channel to channel using one
of three physical methods
bull Time division multiplexing (TDM)
bull Frequency division multiplexing (FDM)
bull Wavelength division multiplexing (WDM)
Bridges
A bridge is a network device that connects different LAN segments using the same accessmethod
Bridges are used to
bull To extend a LAN when the maximum connections limit has been reached
bull To extend a LAN beyond the length limit
bull To segment LANs to reduce data traffic bottlenecks
bull To prevent unauthorized access to LAN (for security)
Standby indicator Pin 36 provides the confirmation signal from the DCE in response to
select standby (pin 32)
Send common Pin 37 provides a common signal return line for unbalanced circuits from
the DTE to the DCE
Electrical Specifications
bull EIA 449 uses two other standards to define its electrical specifications
RS-423 (for unbalanced circuits) and RS-422 (for balanced circuits)
RS-423 Unbalanced Mode
bull An unbalanced circuit specification meaning that it defines only one linefor propagating a signal All signals in this standard use a common return
(or ground) to complete the circuit
RS-422 Balanced Mode
bull A balanced circuit specification meaning that it defines two lines for the propagation of each signal Signals again use a common return (or ground)
for the return of the signal In balanced mode EIA-449 utilizes both pinsin each Category I but does not use the Category II pins The ratio of data
rate to distance is much higher that that of the unbalanced standard or of
EIA-232 10 Mbps for transmission of 40 feet bull In balanced mode two lines carry the same transmission it do not carry
identical signals The signal on one line is the complement of the signal
on the other When plotted the complement looks like a mirror image ofthe original signal Instead of listening to either actual signal the receiver
detects the differences between the two This mechanism makes a balanced circuit less susceptible to noise than an unbalanced circuit and
improves performance
EIA-530
bull A version of EIA-449 that uses DB-25 pins
bull The pin functions of EIA-530 are essentially the same of EIA-449
Category I plus three pins from Category II (the loopback circuits) Other pins in EIA-232 are omitted in EIA-530 such as ring indicator signal
quality detector and data signal rate selector
X21
bull Is an interface standard designed by ITU-T to address many problems
existing in the EIA interfaces and at the same time paves the way for alldigital communications
bull A large proportion of the circuits in the EIA interfaces are used forcontrol since these are necessary to implement control functions as
separate signals With a separate line control information is represented
only by positive and negative voltages But if control signals are encoded
using a meaningful control characters from a system such as ASCII it can be transmitted over data lines
bull X21 eliminates most of the control circuits of the EIA standards and
instead directs its traffic over the data circuits To make this consolidationof functionality possible both the DTE and the DCE must have added
circuit logic that enables them to transform the control codes into bit
streams that can be sent over the data line Both also need additional logicto discriminate between control information and data upon receipt
bull Design of X21 allows not only to use fewer pins but also to be used in
digital telecommunications where control information is sent from deviceto device over a network rather than just between a DTE and a DCE
bull X21 is useful both as an interface to connect digital computers to analogdevices such as modems and as a connector between digital computers and
digital interfaces such as ISDN and X25
Byte Timing
bull Another advantage offered by X21 is that of timing lines to control bytesynchronization in addition to the bit synchronization provided by the EIA
standards By adding a byte timing pulse improves the overall
synchronization of transmissions
Control and indication
bull Pins 3 and 5 of the DB-15 connector are used for the initial handshake or
agreement to begin transmitting Pin 3 is the equivalent of request to send
Pin 5 is the equivalent of clear to send
MODEMbull Modem stands for modulatordemodulator
bull A modulator converts a digital to an analog signalbull A demodulator converts an analog signal to a digital signal
bull The series of 1s and 0s are transformed through the mechanism of ASK
FSK PSK and QAM
Transmission Rate
Bandwidth
bull Every line has upper limit and a lower limit on the frequencies of the
signals it carry this limited range is called the bandwidth
It handles connection establishment and termination data transfer
and packet creation protocols Two types of PLP packets information and control
Up to 4096 channels may be multiplexed at the PLP level Specifies protocols to handle resizing of messages
FRAME RELAY LAYERSbull A technology that operates only at the physical and datalink layers No protocol is
specified for the physical layer the choice is up to the user
bull Eliminates the extensive error checking necessary in X25 protocol
bull It uses simplified version of HDLC protocol in the datalink layerbull It uses routing and switching functions of the datalink layers Frames not packets
are switched
bull It uses PVCs (permanent virtual circuits) Identified through a DLCI (dalta linkconnection identifier)
bull A switch in frame relay performs error checking and routing Error correction is
left to the other protocols at the higher layers
bull Flow control is handled through setting the BECN (backwards explicit congestionnotification) and FECN (forward explicit congestion notification) in the address
field of the frame
bull
ASYNCHRONOUS TRANSFER MODE (ATM)
bull Is the cell relay protocol designed by the ATM forum and adopted by theITU-T
bull In ATM some software functions have moved to hardware this can
increase the data rate
Terms
Cell is the data packet is called a and is composed of 53 bytes (5 bytes of header and 48 bytes of payload) Because each cell is the same size and all are relatively small delay
and other problems associated with multiplexing different sized packets are avoided
A cell network is based on permanent virtual circuit (PVC) routing
bull Virtual Path Identifier (VPI) specifies the path a cell should take
1 Virtual path (VP) switching ndash channels within each VP remain with the VP
2 Virtual path and channel (VPC) switching ndash a channel from one VP may pass into
another VP
IXSDHSONET
Synchronous Optical Network (SONET)
Developed by ANSI
Synchronous Digital Hierarchy (SDH)
Developed by ITU-T
SONETSDH
The two are nearly identical ANSI and ITU-T defined standards that arefundamentally similar and ultimately compatible
Is a synchronous network a single clock is used to handle the timing of
transmissions and equipment across the entire network
SONET
It defines the hierarchy of signals called synchronous transport signals (STS)
Optical carrier (OC) levels are the implementation of STS
SONETSDH Rates
STS OC Rate (Mbps) STM
STS-1 OC-1 5184
STS-3 OC-3 15552 STM-1
STS-9 OC-9 46656 STM-3
STS-12 OC-12 62208 STM-4
STS-18 OC-18 93312 STM-6
STS-24 OC-24 124416 STM-8
STS-36 OC-36 186623 STM-12
STS-48 OC-48 248832 STM-16
STS-96 OC-96 497664 STM-32
STS-192 OC-192 995328 STM-64
STM-synchronous transport module
SONET Four Layers
1 Photonic layer is the lowest and performs physical layer activities
A frame at the photonic layer for STS-1 consists of 6480 bits (8000 framessec)
2-4 Section Line and Path layers correspond to the OSI modelrsquos datalink layer Eachof these layers is responsible for signal transfer across a specific portion of the
1 STS multiplexer combines several optical signals to make an STS signal2 Regenerator removes noise from optical signal
3 Adddrop multiplexer adds STS signals from different paths and removes STS signal
from a path
XTCPIP
Transmission Control ProtocolInternetworking Protocol (TCPIP)
Is a set of rules and procedures that governs the exchange of messages in an
internetwork Originally developed as a protocol for networks that wanted to be connected to
ARPANET a US Department of Defense project now known as Internet
Is a five-layer protocol suite whose bottom four layers match the OSI model fairly
closely The highest level the application layer corresponds to OSIrsquos top threelayers
Internet Protocol (IP) Is defined at the network layer
Unreliable and connectionless Is basically the set of rules for one network communicating with any other To be part of internet organization needs an internet network number unique
number to be included in any packet sent out of the network onto the internet
IP packet is known as datagram consists of a variable header and a variable data
field
IP Address
Uniquely defines the connection of a host to its network The host with more than
one IP address is multi-homed host
IP Addressing
32 bit binary number usually represented as 4 decimal values Equivalent to 4 octets ( 8 bits each decimal value ) Dotted decimal notation Consists of 2 parts the network and the node
Network ndash identifier of particular network on the internet
Host ndash identifier of a particular device which can be a server or a
Peer-to-peer ndash all nodes has equal authority in the networkClient-server ndash a certain node called server has full control over the network and
nodes in the network
LAN Components
1 Server
Is a computer in a network that shared by multiple users
2 Network Interface Card
A printed circuit board that plugs into a network server or client computer It
enables the computer to be physically connected to the network cable which provides the
physical layer connection among the computers in the network It performs electronicfunctions of the access method or datalink protocol
3 HubA device that acts as central connection of certain LAN topology It is capable of
regeneration and switching of signals from one node to another Also known as
concentrator multiple access unit transceiver or repeater
4 Cable
The transmission link in a network These are unshielded twisted pairs (UTP)
shielded twisted pair (STP) coaxial cable and fiber optics cable
5 Connector
The terminating end of the cable to be plug-in or connected to the device
6 Network Operating System (NOS)
The control program that resides in a server or workstation within a LAN Ithandles requests for data transfer from all the users of the networks It interact with the
application programs and the computerrsquos operating system
7 Client
It is the requesting computer from the supplying computers or server
8 Other Peripheral Devices
These are the devices attached to the network such as printers scanners and the
LAN Access Methodrarr it is unnecessary to have a MAC in pt-to-pt full duplex because there are
only two devices on the circuit and full duplex permits either device to
transmit at any time
rarr if it is point-to-point half duplex it needs MAC and also in multipoint full
duplex configurations since several devices share the same channelrarr to ensure that no two devices attempt to transmit data at the same time
1 Controlled Access
a X-on X-off
rarrthe oldest media access control protocols dating back to the days of theteletype
b Polling
rarr the process of sending signal to a terminal to transmit or asking it to receive
rarr it uses ldquoroll call pollingrdquo with scheme or sequence
Node 3its your time to transmitNode 1 its your turn to sendNode 4 you can transmit after node 1
c Token Passing
rarrA channel accessing arrangement that is best suited for ring topology witheither a baseband or broadband network It uses a token and the token circulate in
the network
Token is an electrical signal that circulate around the ring network from onestation to another If the station has the token it can send a message
2 Contention
rarr opposite of controlled access
rarr devices wait until the circuit is free and transmit whenever it has data to send
a Carrier Sense Multiple Access with Collision Detection (CSMACD)
rarrA channel accessing method a node monitors the line to determine if the line is
busy If the station has a message to transmit but the line is busy it waits for an
idle condition before it transmits its message
Collision is the situation when two nodes transmit simultaneously using one link
Backoff Time is the ceasing time before the station attempts to transmit again
Is the process where computers on a token-ring network detect a problem and
attempt to fix it
FDDI (Fiber Distributed Data Interface)
Uses fiber-optic cable and token-passing to create a very fast reliable networkoperating at speeds of 100 Mbps
It includes up to 500 nodes over a distance of 100 km It uses ring topology with two counter-rotating rings It is implement as true physical ring topology A break in a FDDI network results in packets being sent back on the second ring
1 End system (ES) is a network device that does not perform routing or other traffic
forwarding functions Typical ESs include such devices as terminals PCs and printers
2 Intermediate System (IS) is a network device that performs routing or other traffic-forwarding functions it includes devices such as routers switches and bridges
Intradomain IS communicates within a single autonomous system Interdomain IS communicates within and between autonomous systems
3 Area is a logical group of network segments and their attached devices Areas aresubdivisions of autonomous systems
4 Autonomous System (AS) is a collection of networks under a common administrationthat share a common routing strategy Autonomous system are subdivided into areas and
It involves three phases connection establishment- a single path between the
source and the destination systems is determined data transfer ndash transmitted sequentially
over the path that has been established and connection termination ndash termination of paththat has been establish
Connectionless
Offers two important advantages over connection-oriented service dynamic path
selection ndash enables traffic to be routed around network failures because paths are selectedon a packet-to-packet basis dynamic bandwidth allocation ndash used more efficiently
because network resources are not allocated a bandwidth that they will not use
Virtual Circuits
Switched Virtual CircuitA virtual circuit that is dynamically established on demand and terminated when
transmission is completed It has three phases circuit establishment data transfer and
circuit termination
Permanent Virtual Circuit
A permanently established virtual circuit consists of one mode the data transfer
Internetworking Devices
Hubs
bull A hub is a central network device that connects network devices in a startopology
bull Advanced hubs provide very high speed connectivity for FDDI Fast Ethernet
frame relay and ATM networks
bull It is also referred to as a concentrator (or switch) which is a device that can
have multiple inputs and outputs all active at a one time
bull Services offered by hubs
bull Provide a central unit from which to connect multiple nodes into one network
bull Permit large numbers of computers to be connected on single or multipleLANs
bull Reduce network congestion through centralizing network design
bull Provide multiprotocol services such as Ethernet-to-FDDI connectivity
bull Consolidate the network backbone
bull Enable high-speed communications
bull Provide connections for several different media types
bull Multiplexers are network devices that can receive multiple inputs and transmit
them to a shared network medium
bull A multiplexer is a switch that divides a communication medium into multiple
channels so several nodes can communicate at the same time
bull A signal that is multiplexed must be demultiplexed at the other endbull Multiplexers simply are switches used in old and new technology such as the
following
Telephone switching
Switching telecommunications lines to create multiple channels on a
single line Serial communications to enable more than one terminal to
communicate over a single line Fast Ethernet X25 ISDN frame relay ATM and other networking
technologies to create multiple communication channels over a single
communications cable
bull Work at the OSI physical level switching from channel to channel using one
of three physical methods
bull Time division multiplexing (TDM)
bull Frequency division multiplexing (FDM)
bull Wavelength division multiplexing (WDM)
Bridges
A bridge is a network device that connects different LAN segments using the same accessmethod
Bridges are used to
bull To extend a LAN when the maximum connections limit has been reached
bull To extend a LAN beyond the length limit
bull To segment LANs to reduce data traffic bottlenecks
bull To prevent unauthorized access to LAN (for security)
Standby indicator Pin 36 provides the confirmation signal from the DCE in response to
select standby (pin 32)
Send common Pin 37 provides a common signal return line for unbalanced circuits from
the DTE to the DCE
Electrical Specifications
bull EIA 449 uses two other standards to define its electrical specifications
RS-423 (for unbalanced circuits) and RS-422 (for balanced circuits)
RS-423 Unbalanced Mode
bull An unbalanced circuit specification meaning that it defines only one linefor propagating a signal All signals in this standard use a common return
(or ground) to complete the circuit
RS-422 Balanced Mode
bull A balanced circuit specification meaning that it defines two lines for the propagation of each signal Signals again use a common return (or ground)
for the return of the signal In balanced mode EIA-449 utilizes both pinsin each Category I but does not use the Category II pins The ratio of data
rate to distance is much higher that that of the unbalanced standard or of
EIA-232 10 Mbps for transmission of 40 feet bull In balanced mode two lines carry the same transmission it do not carry
identical signals The signal on one line is the complement of the signal
on the other When plotted the complement looks like a mirror image ofthe original signal Instead of listening to either actual signal the receiver
detects the differences between the two This mechanism makes a balanced circuit less susceptible to noise than an unbalanced circuit and
improves performance
EIA-530
bull A version of EIA-449 that uses DB-25 pins
bull The pin functions of EIA-530 are essentially the same of EIA-449
Category I plus three pins from Category II (the loopback circuits) Other pins in EIA-232 are omitted in EIA-530 such as ring indicator signal
quality detector and data signal rate selector
X21
bull Is an interface standard designed by ITU-T to address many problems
existing in the EIA interfaces and at the same time paves the way for alldigital communications
bull A large proportion of the circuits in the EIA interfaces are used forcontrol since these are necessary to implement control functions as
separate signals With a separate line control information is represented
only by positive and negative voltages But if control signals are encoded
using a meaningful control characters from a system such as ASCII it can be transmitted over data lines
bull X21 eliminates most of the control circuits of the EIA standards and
instead directs its traffic over the data circuits To make this consolidationof functionality possible both the DTE and the DCE must have added
circuit logic that enables them to transform the control codes into bit
streams that can be sent over the data line Both also need additional logicto discriminate between control information and data upon receipt
bull Design of X21 allows not only to use fewer pins but also to be used in
digital telecommunications where control information is sent from deviceto device over a network rather than just between a DTE and a DCE
bull X21 is useful both as an interface to connect digital computers to analogdevices such as modems and as a connector between digital computers and
digital interfaces such as ISDN and X25
Byte Timing
bull Another advantage offered by X21 is that of timing lines to control bytesynchronization in addition to the bit synchronization provided by the EIA
standards By adding a byte timing pulse improves the overall
synchronization of transmissions
Control and indication
bull Pins 3 and 5 of the DB-15 connector are used for the initial handshake or
agreement to begin transmitting Pin 3 is the equivalent of request to send
Pin 5 is the equivalent of clear to send
MODEMbull Modem stands for modulatordemodulator
bull A modulator converts a digital to an analog signalbull A demodulator converts an analog signal to a digital signal
bull The series of 1s and 0s are transformed through the mechanism of ASK
FSK PSK and QAM
Transmission Rate
Bandwidth
bull Every line has upper limit and a lower limit on the frequencies of the
signals it carry this limited range is called the bandwidth
It handles connection establishment and termination data transfer
and packet creation protocols Two types of PLP packets information and control
Up to 4096 channels may be multiplexed at the PLP level Specifies protocols to handle resizing of messages
FRAME RELAY LAYERSbull A technology that operates only at the physical and datalink layers No protocol is
specified for the physical layer the choice is up to the user
bull Eliminates the extensive error checking necessary in X25 protocol
bull It uses simplified version of HDLC protocol in the datalink layerbull It uses routing and switching functions of the datalink layers Frames not packets
are switched
bull It uses PVCs (permanent virtual circuits) Identified through a DLCI (dalta linkconnection identifier)
bull A switch in frame relay performs error checking and routing Error correction is
left to the other protocols at the higher layers
bull Flow control is handled through setting the BECN (backwards explicit congestionnotification) and FECN (forward explicit congestion notification) in the address
field of the frame
bull
ASYNCHRONOUS TRANSFER MODE (ATM)
bull Is the cell relay protocol designed by the ATM forum and adopted by theITU-T
bull In ATM some software functions have moved to hardware this can
increase the data rate
Terms
Cell is the data packet is called a and is composed of 53 bytes (5 bytes of header and 48 bytes of payload) Because each cell is the same size and all are relatively small delay
and other problems associated with multiplexing different sized packets are avoided
A cell network is based on permanent virtual circuit (PVC) routing
bull Virtual Path Identifier (VPI) specifies the path a cell should take
1 Virtual path (VP) switching ndash channels within each VP remain with the VP
2 Virtual path and channel (VPC) switching ndash a channel from one VP may pass into
another VP
IXSDHSONET
Synchronous Optical Network (SONET)
Developed by ANSI
Synchronous Digital Hierarchy (SDH)
Developed by ITU-T
SONETSDH
The two are nearly identical ANSI and ITU-T defined standards that arefundamentally similar and ultimately compatible
Is a synchronous network a single clock is used to handle the timing of
transmissions and equipment across the entire network
SONET
It defines the hierarchy of signals called synchronous transport signals (STS)
Optical carrier (OC) levels are the implementation of STS
SONETSDH Rates
STS OC Rate (Mbps) STM
STS-1 OC-1 5184
STS-3 OC-3 15552 STM-1
STS-9 OC-9 46656 STM-3
STS-12 OC-12 62208 STM-4
STS-18 OC-18 93312 STM-6
STS-24 OC-24 124416 STM-8
STS-36 OC-36 186623 STM-12
STS-48 OC-48 248832 STM-16
STS-96 OC-96 497664 STM-32
STS-192 OC-192 995328 STM-64
STM-synchronous transport module
SONET Four Layers
1 Photonic layer is the lowest and performs physical layer activities
A frame at the photonic layer for STS-1 consists of 6480 bits (8000 framessec)
2-4 Section Line and Path layers correspond to the OSI modelrsquos datalink layer Eachof these layers is responsible for signal transfer across a specific portion of the
1 STS multiplexer combines several optical signals to make an STS signal2 Regenerator removes noise from optical signal
3 Adddrop multiplexer adds STS signals from different paths and removes STS signal
from a path
XTCPIP
Transmission Control ProtocolInternetworking Protocol (TCPIP)
Is a set of rules and procedures that governs the exchange of messages in an
internetwork Originally developed as a protocol for networks that wanted to be connected to
ARPANET a US Department of Defense project now known as Internet
Is a five-layer protocol suite whose bottom four layers match the OSI model fairly
closely The highest level the application layer corresponds to OSIrsquos top threelayers
Internet Protocol (IP) Is defined at the network layer
Unreliable and connectionless Is basically the set of rules for one network communicating with any other To be part of internet organization needs an internet network number unique
number to be included in any packet sent out of the network onto the internet
IP packet is known as datagram consists of a variable header and a variable data
field
IP Address
Uniquely defines the connection of a host to its network The host with more than
one IP address is multi-homed host
IP Addressing
32 bit binary number usually represented as 4 decimal values Equivalent to 4 octets ( 8 bits each decimal value ) Dotted decimal notation Consists of 2 parts the network and the node
Network ndash identifier of particular network on the internet
Host ndash identifier of a particular device which can be a server or a
LAN Access Methodrarr it is unnecessary to have a MAC in pt-to-pt full duplex because there are
only two devices on the circuit and full duplex permits either device to
transmit at any time
rarr if it is point-to-point half duplex it needs MAC and also in multipoint full
duplex configurations since several devices share the same channelrarr to ensure that no two devices attempt to transmit data at the same time
1 Controlled Access
a X-on X-off
rarrthe oldest media access control protocols dating back to the days of theteletype
b Polling
rarr the process of sending signal to a terminal to transmit or asking it to receive
rarr it uses ldquoroll call pollingrdquo with scheme or sequence
Node 3its your time to transmitNode 1 its your turn to sendNode 4 you can transmit after node 1
c Token Passing
rarrA channel accessing arrangement that is best suited for ring topology witheither a baseband or broadband network It uses a token and the token circulate in
the network
Token is an electrical signal that circulate around the ring network from onestation to another If the station has the token it can send a message
2 Contention
rarr opposite of controlled access
rarr devices wait until the circuit is free and transmit whenever it has data to send
a Carrier Sense Multiple Access with Collision Detection (CSMACD)
rarrA channel accessing method a node monitors the line to determine if the line is
busy If the station has a message to transmit but the line is busy it waits for an
idle condition before it transmits its message
Collision is the situation when two nodes transmit simultaneously using one link
Backoff Time is the ceasing time before the station attempts to transmit again
Is the process where computers on a token-ring network detect a problem and
attempt to fix it
FDDI (Fiber Distributed Data Interface)
Uses fiber-optic cable and token-passing to create a very fast reliable networkoperating at speeds of 100 Mbps
It includes up to 500 nodes over a distance of 100 km It uses ring topology with two counter-rotating rings It is implement as true physical ring topology A break in a FDDI network results in packets being sent back on the second ring
1 End system (ES) is a network device that does not perform routing or other traffic
forwarding functions Typical ESs include such devices as terminals PCs and printers
2 Intermediate System (IS) is a network device that performs routing or other traffic-forwarding functions it includes devices such as routers switches and bridges
Intradomain IS communicates within a single autonomous system Interdomain IS communicates within and between autonomous systems
3 Area is a logical group of network segments and their attached devices Areas aresubdivisions of autonomous systems
4 Autonomous System (AS) is a collection of networks under a common administrationthat share a common routing strategy Autonomous system are subdivided into areas and
It involves three phases connection establishment- a single path between the
source and the destination systems is determined data transfer ndash transmitted sequentially
over the path that has been established and connection termination ndash termination of paththat has been establish
Connectionless
Offers two important advantages over connection-oriented service dynamic path
selection ndash enables traffic to be routed around network failures because paths are selectedon a packet-to-packet basis dynamic bandwidth allocation ndash used more efficiently
because network resources are not allocated a bandwidth that they will not use
Virtual Circuits
Switched Virtual CircuitA virtual circuit that is dynamically established on demand and terminated when
transmission is completed It has three phases circuit establishment data transfer and
circuit termination
Permanent Virtual Circuit
A permanently established virtual circuit consists of one mode the data transfer
Internetworking Devices
Hubs
bull A hub is a central network device that connects network devices in a startopology
bull Advanced hubs provide very high speed connectivity for FDDI Fast Ethernet
frame relay and ATM networks
bull It is also referred to as a concentrator (or switch) which is a device that can
have multiple inputs and outputs all active at a one time
bull Services offered by hubs
bull Provide a central unit from which to connect multiple nodes into one network
bull Permit large numbers of computers to be connected on single or multipleLANs
bull Reduce network congestion through centralizing network design
bull Provide multiprotocol services such as Ethernet-to-FDDI connectivity
bull Consolidate the network backbone
bull Enable high-speed communications
bull Provide connections for several different media types
bull Multiplexers are network devices that can receive multiple inputs and transmit
them to a shared network medium
bull A multiplexer is a switch that divides a communication medium into multiple
channels so several nodes can communicate at the same time
bull A signal that is multiplexed must be demultiplexed at the other endbull Multiplexers simply are switches used in old and new technology such as the
following
Telephone switching
Switching telecommunications lines to create multiple channels on a
single line Serial communications to enable more than one terminal to
communicate over a single line Fast Ethernet X25 ISDN frame relay ATM and other networking
technologies to create multiple communication channels over a single
communications cable
bull Work at the OSI physical level switching from channel to channel using one
of three physical methods
bull Time division multiplexing (TDM)
bull Frequency division multiplexing (FDM)
bull Wavelength division multiplexing (WDM)
Bridges
A bridge is a network device that connects different LAN segments using the same accessmethod
Bridges are used to
bull To extend a LAN when the maximum connections limit has been reached
bull To extend a LAN beyond the length limit
bull To segment LANs to reduce data traffic bottlenecks
bull To prevent unauthorized access to LAN (for security)
Standby indicator Pin 36 provides the confirmation signal from the DCE in response to
select standby (pin 32)
Send common Pin 37 provides a common signal return line for unbalanced circuits from
the DTE to the DCE
Electrical Specifications
bull EIA 449 uses two other standards to define its electrical specifications
RS-423 (for unbalanced circuits) and RS-422 (for balanced circuits)
RS-423 Unbalanced Mode
bull An unbalanced circuit specification meaning that it defines only one linefor propagating a signal All signals in this standard use a common return
(or ground) to complete the circuit
RS-422 Balanced Mode
bull A balanced circuit specification meaning that it defines two lines for the propagation of each signal Signals again use a common return (or ground)
for the return of the signal In balanced mode EIA-449 utilizes both pinsin each Category I but does not use the Category II pins The ratio of data
rate to distance is much higher that that of the unbalanced standard or of
EIA-232 10 Mbps for transmission of 40 feet bull In balanced mode two lines carry the same transmission it do not carry
identical signals The signal on one line is the complement of the signal
on the other When plotted the complement looks like a mirror image ofthe original signal Instead of listening to either actual signal the receiver
detects the differences between the two This mechanism makes a balanced circuit less susceptible to noise than an unbalanced circuit and
improves performance
EIA-530
bull A version of EIA-449 that uses DB-25 pins
bull The pin functions of EIA-530 are essentially the same of EIA-449
Category I plus three pins from Category II (the loopback circuits) Other pins in EIA-232 are omitted in EIA-530 such as ring indicator signal
quality detector and data signal rate selector
X21
bull Is an interface standard designed by ITU-T to address many problems
existing in the EIA interfaces and at the same time paves the way for alldigital communications
bull A large proportion of the circuits in the EIA interfaces are used forcontrol since these are necessary to implement control functions as
separate signals With a separate line control information is represented
only by positive and negative voltages But if control signals are encoded
using a meaningful control characters from a system such as ASCII it can be transmitted over data lines
bull X21 eliminates most of the control circuits of the EIA standards and
instead directs its traffic over the data circuits To make this consolidationof functionality possible both the DTE and the DCE must have added
circuit logic that enables them to transform the control codes into bit
streams that can be sent over the data line Both also need additional logicto discriminate between control information and data upon receipt
bull Design of X21 allows not only to use fewer pins but also to be used in
digital telecommunications where control information is sent from deviceto device over a network rather than just between a DTE and a DCE
bull X21 is useful both as an interface to connect digital computers to analogdevices such as modems and as a connector between digital computers and
digital interfaces such as ISDN and X25
Byte Timing
bull Another advantage offered by X21 is that of timing lines to control bytesynchronization in addition to the bit synchronization provided by the EIA
standards By adding a byte timing pulse improves the overall
synchronization of transmissions
Control and indication
bull Pins 3 and 5 of the DB-15 connector are used for the initial handshake or
agreement to begin transmitting Pin 3 is the equivalent of request to send
Pin 5 is the equivalent of clear to send
MODEMbull Modem stands for modulatordemodulator
bull A modulator converts a digital to an analog signalbull A demodulator converts an analog signal to a digital signal
bull The series of 1s and 0s are transformed through the mechanism of ASK
FSK PSK and QAM
Transmission Rate
Bandwidth
bull Every line has upper limit and a lower limit on the frequencies of the
signals it carry this limited range is called the bandwidth
It handles connection establishment and termination data transfer
and packet creation protocols Two types of PLP packets information and control
Up to 4096 channels may be multiplexed at the PLP level Specifies protocols to handle resizing of messages
FRAME RELAY LAYERSbull A technology that operates only at the physical and datalink layers No protocol is
specified for the physical layer the choice is up to the user
bull Eliminates the extensive error checking necessary in X25 protocol
bull It uses simplified version of HDLC protocol in the datalink layerbull It uses routing and switching functions of the datalink layers Frames not packets
are switched
bull It uses PVCs (permanent virtual circuits) Identified through a DLCI (dalta linkconnection identifier)
bull A switch in frame relay performs error checking and routing Error correction is
left to the other protocols at the higher layers
bull Flow control is handled through setting the BECN (backwards explicit congestionnotification) and FECN (forward explicit congestion notification) in the address
field of the frame
bull
ASYNCHRONOUS TRANSFER MODE (ATM)
bull Is the cell relay protocol designed by the ATM forum and adopted by theITU-T
bull In ATM some software functions have moved to hardware this can
increase the data rate
Terms
Cell is the data packet is called a and is composed of 53 bytes (5 bytes of header and 48 bytes of payload) Because each cell is the same size and all are relatively small delay
and other problems associated with multiplexing different sized packets are avoided
A cell network is based on permanent virtual circuit (PVC) routing
bull Virtual Path Identifier (VPI) specifies the path a cell should take
1 Virtual path (VP) switching ndash channels within each VP remain with the VP
2 Virtual path and channel (VPC) switching ndash a channel from one VP may pass into
another VP
IXSDHSONET
Synchronous Optical Network (SONET)
Developed by ANSI
Synchronous Digital Hierarchy (SDH)
Developed by ITU-T
SONETSDH
The two are nearly identical ANSI and ITU-T defined standards that arefundamentally similar and ultimately compatible
Is a synchronous network a single clock is used to handle the timing of
transmissions and equipment across the entire network
SONET
It defines the hierarchy of signals called synchronous transport signals (STS)
Optical carrier (OC) levels are the implementation of STS
SONETSDH Rates
STS OC Rate (Mbps) STM
STS-1 OC-1 5184
STS-3 OC-3 15552 STM-1
STS-9 OC-9 46656 STM-3
STS-12 OC-12 62208 STM-4
STS-18 OC-18 93312 STM-6
STS-24 OC-24 124416 STM-8
STS-36 OC-36 186623 STM-12
STS-48 OC-48 248832 STM-16
STS-96 OC-96 497664 STM-32
STS-192 OC-192 995328 STM-64
STM-synchronous transport module
SONET Four Layers
1 Photonic layer is the lowest and performs physical layer activities
A frame at the photonic layer for STS-1 consists of 6480 bits (8000 framessec)
2-4 Section Line and Path layers correspond to the OSI modelrsquos datalink layer Eachof these layers is responsible for signal transfer across a specific portion of the
1 STS multiplexer combines several optical signals to make an STS signal2 Regenerator removes noise from optical signal
3 Adddrop multiplexer adds STS signals from different paths and removes STS signal
from a path
XTCPIP
Transmission Control ProtocolInternetworking Protocol (TCPIP)
Is a set of rules and procedures that governs the exchange of messages in an
internetwork Originally developed as a protocol for networks that wanted to be connected to
ARPANET a US Department of Defense project now known as Internet
Is a five-layer protocol suite whose bottom four layers match the OSI model fairly
closely The highest level the application layer corresponds to OSIrsquos top threelayers
Internet Protocol (IP) Is defined at the network layer
Unreliable and connectionless Is basically the set of rules for one network communicating with any other To be part of internet organization needs an internet network number unique
number to be included in any packet sent out of the network onto the internet
IP packet is known as datagram consists of a variable header and a variable data
field
IP Address
Uniquely defines the connection of a host to its network The host with more than
one IP address is multi-homed host
IP Addressing
32 bit binary number usually represented as 4 decimal values Equivalent to 4 octets ( 8 bits each decimal value ) Dotted decimal notation Consists of 2 parts the network and the node
Network ndash identifier of particular network on the internet
Host ndash identifier of a particular device which can be a server or a
LAN Access Methodrarr it is unnecessary to have a MAC in pt-to-pt full duplex because there are
only two devices on the circuit and full duplex permits either device to
transmit at any time
rarr if it is point-to-point half duplex it needs MAC and also in multipoint full
duplex configurations since several devices share the same channelrarr to ensure that no two devices attempt to transmit data at the same time
1 Controlled Access
a X-on X-off
rarrthe oldest media access control protocols dating back to the days of theteletype
b Polling
rarr the process of sending signal to a terminal to transmit or asking it to receive
rarr it uses ldquoroll call pollingrdquo with scheme or sequence
Node 3its your time to transmitNode 1 its your turn to sendNode 4 you can transmit after node 1
c Token Passing
rarrA channel accessing arrangement that is best suited for ring topology witheither a baseband or broadband network It uses a token and the token circulate in
the network
Token is an electrical signal that circulate around the ring network from onestation to another If the station has the token it can send a message
2 Contention
rarr opposite of controlled access
rarr devices wait until the circuit is free and transmit whenever it has data to send
a Carrier Sense Multiple Access with Collision Detection (CSMACD)
rarrA channel accessing method a node monitors the line to determine if the line is
busy If the station has a message to transmit but the line is busy it waits for an
idle condition before it transmits its message
Collision is the situation when two nodes transmit simultaneously using one link
Backoff Time is the ceasing time before the station attempts to transmit again
Is the process where computers on a token-ring network detect a problem and
attempt to fix it
FDDI (Fiber Distributed Data Interface)
Uses fiber-optic cable and token-passing to create a very fast reliable networkoperating at speeds of 100 Mbps
It includes up to 500 nodes over a distance of 100 km It uses ring topology with two counter-rotating rings It is implement as true physical ring topology A break in a FDDI network results in packets being sent back on the second ring
1 End system (ES) is a network device that does not perform routing or other traffic
forwarding functions Typical ESs include such devices as terminals PCs and printers
2 Intermediate System (IS) is a network device that performs routing or other traffic-forwarding functions it includes devices such as routers switches and bridges
Intradomain IS communicates within a single autonomous system Interdomain IS communicates within and between autonomous systems
3 Area is a logical group of network segments and their attached devices Areas aresubdivisions of autonomous systems
4 Autonomous System (AS) is a collection of networks under a common administrationthat share a common routing strategy Autonomous system are subdivided into areas and
It involves three phases connection establishment- a single path between the
source and the destination systems is determined data transfer ndash transmitted sequentially
over the path that has been established and connection termination ndash termination of paththat has been establish
Connectionless
Offers two important advantages over connection-oriented service dynamic path
selection ndash enables traffic to be routed around network failures because paths are selectedon a packet-to-packet basis dynamic bandwidth allocation ndash used more efficiently
because network resources are not allocated a bandwidth that they will not use
Virtual Circuits
Switched Virtual CircuitA virtual circuit that is dynamically established on demand and terminated when
transmission is completed It has three phases circuit establishment data transfer and
circuit termination
Permanent Virtual Circuit
A permanently established virtual circuit consists of one mode the data transfer
Internetworking Devices
Hubs
bull A hub is a central network device that connects network devices in a startopology
bull Advanced hubs provide very high speed connectivity for FDDI Fast Ethernet
frame relay and ATM networks
bull It is also referred to as a concentrator (or switch) which is a device that can
have multiple inputs and outputs all active at a one time
bull Services offered by hubs
bull Provide a central unit from which to connect multiple nodes into one network
bull Permit large numbers of computers to be connected on single or multipleLANs
bull Reduce network congestion through centralizing network design
bull Provide multiprotocol services such as Ethernet-to-FDDI connectivity
bull Consolidate the network backbone
bull Enable high-speed communications
bull Provide connections for several different media types
bull Multiplexers are network devices that can receive multiple inputs and transmit
them to a shared network medium
bull A multiplexer is a switch that divides a communication medium into multiple
channels so several nodes can communicate at the same time
bull A signal that is multiplexed must be demultiplexed at the other endbull Multiplexers simply are switches used in old and new technology such as the
following
Telephone switching
Switching telecommunications lines to create multiple channels on a
single line Serial communications to enable more than one terminal to
communicate over a single line Fast Ethernet X25 ISDN frame relay ATM and other networking
technologies to create multiple communication channels over a single
communications cable
bull Work at the OSI physical level switching from channel to channel using one
of three physical methods
bull Time division multiplexing (TDM)
bull Frequency division multiplexing (FDM)
bull Wavelength division multiplexing (WDM)
Bridges
A bridge is a network device that connects different LAN segments using the same accessmethod
Bridges are used to
bull To extend a LAN when the maximum connections limit has been reached
bull To extend a LAN beyond the length limit
bull To segment LANs to reduce data traffic bottlenecks
bull To prevent unauthorized access to LAN (for security)
Standby indicator Pin 36 provides the confirmation signal from the DCE in response to
select standby (pin 32)
Send common Pin 37 provides a common signal return line for unbalanced circuits from
the DTE to the DCE
Electrical Specifications
bull EIA 449 uses two other standards to define its electrical specifications
RS-423 (for unbalanced circuits) and RS-422 (for balanced circuits)
RS-423 Unbalanced Mode
bull An unbalanced circuit specification meaning that it defines only one linefor propagating a signal All signals in this standard use a common return
(or ground) to complete the circuit
RS-422 Balanced Mode
bull A balanced circuit specification meaning that it defines two lines for the propagation of each signal Signals again use a common return (or ground)
for the return of the signal In balanced mode EIA-449 utilizes both pinsin each Category I but does not use the Category II pins The ratio of data
rate to distance is much higher that that of the unbalanced standard or of
EIA-232 10 Mbps for transmission of 40 feet bull In balanced mode two lines carry the same transmission it do not carry
identical signals The signal on one line is the complement of the signal
on the other When plotted the complement looks like a mirror image ofthe original signal Instead of listening to either actual signal the receiver
detects the differences between the two This mechanism makes a balanced circuit less susceptible to noise than an unbalanced circuit and
improves performance
EIA-530
bull A version of EIA-449 that uses DB-25 pins
bull The pin functions of EIA-530 are essentially the same of EIA-449
Category I plus three pins from Category II (the loopback circuits) Other pins in EIA-232 are omitted in EIA-530 such as ring indicator signal
quality detector and data signal rate selector
X21
bull Is an interface standard designed by ITU-T to address many problems
existing in the EIA interfaces and at the same time paves the way for alldigital communications
bull A large proportion of the circuits in the EIA interfaces are used forcontrol since these are necessary to implement control functions as
separate signals With a separate line control information is represented
only by positive and negative voltages But if control signals are encoded
using a meaningful control characters from a system such as ASCII it can be transmitted over data lines
bull X21 eliminates most of the control circuits of the EIA standards and
instead directs its traffic over the data circuits To make this consolidationof functionality possible both the DTE and the DCE must have added
circuit logic that enables them to transform the control codes into bit
streams that can be sent over the data line Both also need additional logicto discriminate between control information and data upon receipt
bull Design of X21 allows not only to use fewer pins but also to be used in
digital telecommunications where control information is sent from deviceto device over a network rather than just between a DTE and a DCE
bull X21 is useful both as an interface to connect digital computers to analogdevices such as modems and as a connector between digital computers and
digital interfaces such as ISDN and X25
Byte Timing
bull Another advantage offered by X21 is that of timing lines to control bytesynchronization in addition to the bit synchronization provided by the EIA
standards By adding a byte timing pulse improves the overall
synchronization of transmissions
Control and indication
bull Pins 3 and 5 of the DB-15 connector are used for the initial handshake or
agreement to begin transmitting Pin 3 is the equivalent of request to send
Pin 5 is the equivalent of clear to send
MODEMbull Modem stands for modulatordemodulator
bull A modulator converts a digital to an analog signalbull A demodulator converts an analog signal to a digital signal
bull The series of 1s and 0s are transformed through the mechanism of ASK
FSK PSK and QAM
Transmission Rate
Bandwidth
bull Every line has upper limit and a lower limit on the frequencies of the
signals it carry this limited range is called the bandwidth
It handles connection establishment and termination data transfer
and packet creation protocols Two types of PLP packets information and control
Up to 4096 channels may be multiplexed at the PLP level Specifies protocols to handle resizing of messages
FRAME RELAY LAYERSbull A technology that operates only at the physical and datalink layers No protocol is
specified for the physical layer the choice is up to the user
bull Eliminates the extensive error checking necessary in X25 protocol
bull It uses simplified version of HDLC protocol in the datalink layerbull It uses routing and switching functions of the datalink layers Frames not packets
are switched
bull It uses PVCs (permanent virtual circuits) Identified through a DLCI (dalta linkconnection identifier)
bull A switch in frame relay performs error checking and routing Error correction is
left to the other protocols at the higher layers
bull Flow control is handled through setting the BECN (backwards explicit congestionnotification) and FECN (forward explicit congestion notification) in the address
field of the frame
bull
ASYNCHRONOUS TRANSFER MODE (ATM)
bull Is the cell relay protocol designed by the ATM forum and adopted by theITU-T
bull In ATM some software functions have moved to hardware this can
increase the data rate
Terms
Cell is the data packet is called a and is composed of 53 bytes (5 bytes of header and 48 bytes of payload) Because each cell is the same size and all are relatively small delay
and other problems associated with multiplexing different sized packets are avoided
A cell network is based on permanent virtual circuit (PVC) routing
bull Virtual Path Identifier (VPI) specifies the path a cell should take
1 Virtual path (VP) switching ndash channels within each VP remain with the VP
2 Virtual path and channel (VPC) switching ndash a channel from one VP may pass into
another VP
IXSDHSONET
Synchronous Optical Network (SONET)
Developed by ANSI
Synchronous Digital Hierarchy (SDH)
Developed by ITU-T
SONETSDH
The two are nearly identical ANSI and ITU-T defined standards that arefundamentally similar and ultimately compatible
Is a synchronous network a single clock is used to handle the timing of
transmissions and equipment across the entire network
SONET
It defines the hierarchy of signals called synchronous transport signals (STS)
Optical carrier (OC) levels are the implementation of STS
SONETSDH Rates
STS OC Rate (Mbps) STM
STS-1 OC-1 5184
STS-3 OC-3 15552 STM-1
STS-9 OC-9 46656 STM-3
STS-12 OC-12 62208 STM-4
STS-18 OC-18 93312 STM-6
STS-24 OC-24 124416 STM-8
STS-36 OC-36 186623 STM-12
STS-48 OC-48 248832 STM-16
STS-96 OC-96 497664 STM-32
STS-192 OC-192 995328 STM-64
STM-synchronous transport module
SONET Four Layers
1 Photonic layer is the lowest and performs physical layer activities
A frame at the photonic layer for STS-1 consists of 6480 bits (8000 framessec)
2-4 Section Line and Path layers correspond to the OSI modelrsquos datalink layer Eachof these layers is responsible for signal transfer across a specific portion of the
1 STS multiplexer combines several optical signals to make an STS signal2 Regenerator removes noise from optical signal
3 Adddrop multiplexer adds STS signals from different paths and removes STS signal
from a path
XTCPIP
Transmission Control ProtocolInternetworking Protocol (TCPIP)
Is a set of rules and procedures that governs the exchange of messages in an
internetwork Originally developed as a protocol for networks that wanted to be connected to
ARPANET a US Department of Defense project now known as Internet
Is a five-layer protocol suite whose bottom four layers match the OSI model fairly
closely The highest level the application layer corresponds to OSIrsquos top threelayers
Internet Protocol (IP) Is defined at the network layer
Unreliable and connectionless Is basically the set of rules for one network communicating with any other To be part of internet organization needs an internet network number unique
number to be included in any packet sent out of the network onto the internet
IP packet is known as datagram consists of a variable header and a variable data
field
IP Address
Uniquely defines the connection of a host to its network The host with more than
one IP address is multi-homed host
IP Addressing
32 bit binary number usually represented as 4 decimal values Equivalent to 4 octets ( 8 bits each decimal value ) Dotted decimal notation Consists of 2 parts the network and the node
Network ndash identifier of particular network on the internet
Host ndash identifier of a particular device which can be a server or a
LAN Access Methodrarr it is unnecessary to have a MAC in pt-to-pt full duplex because there are
only two devices on the circuit and full duplex permits either device to
transmit at any time
rarr if it is point-to-point half duplex it needs MAC and also in multipoint full
duplex configurations since several devices share the same channelrarr to ensure that no two devices attempt to transmit data at the same time
1 Controlled Access
a X-on X-off
rarrthe oldest media access control protocols dating back to the days of theteletype
b Polling
rarr the process of sending signal to a terminal to transmit or asking it to receive
rarr it uses ldquoroll call pollingrdquo with scheme or sequence
Node 3its your time to transmitNode 1 its your turn to sendNode 4 you can transmit after node 1
c Token Passing
rarrA channel accessing arrangement that is best suited for ring topology witheither a baseband or broadband network It uses a token and the token circulate in
the network
Token is an electrical signal that circulate around the ring network from onestation to another If the station has the token it can send a message
2 Contention
rarr opposite of controlled access
rarr devices wait until the circuit is free and transmit whenever it has data to send
a Carrier Sense Multiple Access with Collision Detection (CSMACD)
rarrA channel accessing method a node monitors the line to determine if the line is
busy If the station has a message to transmit but the line is busy it waits for an
idle condition before it transmits its message
Collision is the situation when two nodes transmit simultaneously using one link
Backoff Time is the ceasing time before the station attempts to transmit again
Is the process where computers on a token-ring network detect a problem and
attempt to fix it
FDDI (Fiber Distributed Data Interface)
Uses fiber-optic cable and token-passing to create a very fast reliable networkoperating at speeds of 100 Mbps
It includes up to 500 nodes over a distance of 100 km It uses ring topology with two counter-rotating rings It is implement as true physical ring topology A break in a FDDI network results in packets being sent back on the second ring
1 End system (ES) is a network device that does not perform routing or other traffic
forwarding functions Typical ESs include such devices as terminals PCs and printers
2 Intermediate System (IS) is a network device that performs routing or other traffic-forwarding functions it includes devices such as routers switches and bridges
Intradomain IS communicates within a single autonomous system Interdomain IS communicates within and between autonomous systems
3 Area is a logical group of network segments and their attached devices Areas aresubdivisions of autonomous systems
4 Autonomous System (AS) is a collection of networks under a common administrationthat share a common routing strategy Autonomous system are subdivided into areas and
It involves three phases connection establishment- a single path between the
source and the destination systems is determined data transfer ndash transmitted sequentially
over the path that has been established and connection termination ndash termination of paththat has been establish
Connectionless
Offers two important advantages over connection-oriented service dynamic path
selection ndash enables traffic to be routed around network failures because paths are selectedon a packet-to-packet basis dynamic bandwidth allocation ndash used more efficiently
because network resources are not allocated a bandwidth that they will not use
Virtual Circuits
Switched Virtual CircuitA virtual circuit that is dynamically established on demand and terminated when
transmission is completed It has three phases circuit establishment data transfer and
circuit termination
Permanent Virtual Circuit
A permanently established virtual circuit consists of one mode the data transfer
Internetworking Devices
Hubs
bull A hub is a central network device that connects network devices in a startopology
bull Advanced hubs provide very high speed connectivity for FDDI Fast Ethernet
frame relay and ATM networks
bull It is also referred to as a concentrator (or switch) which is a device that can
have multiple inputs and outputs all active at a one time
bull Services offered by hubs
bull Provide a central unit from which to connect multiple nodes into one network
bull Permit large numbers of computers to be connected on single or multipleLANs
bull Reduce network congestion through centralizing network design
bull Provide multiprotocol services such as Ethernet-to-FDDI connectivity
bull Consolidate the network backbone
bull Enable high-speed communications
bull Provide connections for several different media types
bull Multiplexers are network devices that can receive multiple inputs and transmit
them to a shared network medium
bull A multiplexer is a switch that divides a communication medium into multiple
channels so several nodes can communicate at the same time
bull A signal that is multiplexed must be demultiplexed at the other endbull Multiplexers simply are switches used in old and new technology such as the
following
Telephone switching
Switching telecommunications lines to create multiple channels on a
single line Serial communications to enable more than one terminal to
communicate over a single line Fast Ethernet X25 ISDN frame relay ATM and other networking
technologies to create multiple communication channels over a single
communications cable
bull Work at the OSI physical level switching from channel to channel using one
of three physical methods
bull Time division multiplexing (TDM)
bull Frequency division multiplexing (FDM)
bull Wavelength division multiplexing (WDM)
Bridges
A bridge is a network device that connects different LAN segments using the same accessmethod
Bridges are used to
bull To extend a LAN when the maximum connections limit has been reached
bull To extend a LAN beyond the length limit
bull To segment LANs to reduce data traffic bottlenecks
bull To prevent unauthorized access to LAN (for security)
Standby indicator Pin 36 provides the confirmation signal from the DCE in response to
select standby (pin 32)
Send common Pin 37 provides a common signal return line for unbalanced circuits from
the DTE to the DCE
Electrical Specifications
bull EIA 449 uses two other standards to define its electrical specifications
RS-423 (for unbalanced circuits) and RS-422 (for balanced circuits)
RS-423 Unbalanced Mode
bull An unbalanced circuit specification meaning that it defines only one linefor propagating a signal All signals in this standard use a common return
(or ground) to complete the circuit
RS-422 Balanced Mode
bull A balanced circuit specification meaning that it defines two lines for the propagation of each signal Signals again use a common return (or ground)
for the return of the signal In balanced mode EIA-449 utilizes both pinsin each Category I but does not use the Category II pins The ratio of data
rate to distance is much higher that that of the unbalanced standard or of
EIA-232 10 Mbps for transmission of 40 feet bull In balanced mode two lines carry the same transmission it do not carry
identical signals The signal on one line is the complement of the signal
on the other When plotted the complement looks like a mirror image ofthe original signal Instead of listening to either actual signal the receiver
detects the differences between the two This mechanism makes a balanced circuit less susceptible to noise than an unbalanced circuit and
improves performance
EIA-530
bull A version of EIA-449 that uses DB-25 pins
bull The pin functions of EIA-530 are essentially the same of EIA-449
Category I plus three pins from Category II (the loopback circuits) Other pins in EIA-232 are omitted in EIA-530 such as ring indicator signal
quality detector and data signal rate selector
X21
bull Is an interface standard designed by ITU-T to address many problems
existing in the EIA interfaces and at the same time paves the way for alldigital communications
bull A large proportion of the circuits in the EIA interfaces are used forcontrol since these are necessary to implement control functions as
separate signals With a separate line control information is represented
only by positive and negative voltages But if control signals are encoded
using a meaningful control characters from a system such as ASCII it can be transmitted over data lines
bull X21 eliminates most of the control circuits of the EIA standards and
instead directs its traffic over the data circuits To make this consolidationof functionality possible both the DTE and the DCE must have added
circuit logic that enables them to transform the control codes into bit
streams that can be sent over the data line Both also need additional logicto discriminate between control information and data upon receipt
bull Design of X21 allows not only to use fewer pins but also to be used in
digital telecommunications where control information is sent from deviceto device over a network rather than just between a DTE and a DCE
bull X21 is useful both as an interface to connect digital computers to analogdevices such as modems and as a connector between digital computers and
digital interfaces such as ISDN and X25
Byte Timing
bull Another advantage offered by X21 is that of timing lines to control bytesynchronization in addition to the bit synchronization provided by the EIA
standards By adding a byte timing pulse improves the overall
synchronization of transmissions
Control and indication
bull Pins 3 and 5 of the DB-15 connector are used for the initial handshake or
agreement to begin transmitting Pin 3 is the equivalent of request to send
Pin 5 is the equivalent of clear to send
MODEMbull Modem stands for modulatordemodulator
bull A modulator converts a digital to an analog signalbull A demodulator converts an analog signal to a digital signal
bull The series of 1s and 0s are transformed through the mechanism of ASK
FSK PSK and QAM
Transmission Rate
Bandwidth
bull Every line has upper limit and a lower limit on the frequencies of the
signals it carry this limited range is called the bandwidth
It handles connection establishment and termination data transfer
and packet creation protocols Two types of PLP packets information and control
Up to 4096 channels may be multiplexed at the PLP level Specifies protocols to handle resizing of messages
FRAME RELAY LAYERSbull A technology that operates only at the physical and datalink layers No protocol is
specified for the physical layer the choice is up to the user
bull Eliminates the extensive error checking necessary in X25 protocol
bull It uses simplified version of HDLC protocol in the datalink layerbull It uses routing and switching functions of the datalink layers Frames not packets
are switched
bull It uses PVCs (permanent virtual circuits) Identified through a DLCI (dalta linkconnection identifier)
bull A switch in frame relay performs error checking and routing Error correction is
left to the other protocols at the higher layers
bull Flow control is handled through setting the BECN (backwards explicit congestionnotification) and FECN (forward explicit congestion notification) in the address
field of the frame
bull
ASYNCHRONOUS TRANSFER MODE (ATM)
bull Is the cell relay protocol designed by the ATM forum and adopted by theITU-T
bull In ATM some software functions have moved to hardware this can
increase the data rate
Terms
Cell is the data packet is called a and is composed of 53 bytes (5 bytes of header and 48 bytes of payload) Because each cell is the same size and all are relatively small delay
and other problems associated with multiplexing different sized packets are avoided
A cell network is based on permanent virtual circuit (PVC) routing
bull Virtual Path Identifier (VPI) specifies the path a cell should take
1 Virtual path (VP) switching ndash channels within each VP remain with the VP
2 Virtual path and channel (VPC) switching ndash a channel from one VP may pass into
another VP
IXSDHSONET
Synchronous Optical Network (SONET)
Developed by ANSI
Synchronous Digital Hierarchy (SDH)
Developed by ITU-T
SONETSDH
The two are nearly identical ANSI and ITU-T defined standards that arefundamentally similar and ultimately compatible
Is a synchronous network a single clock is used to handle the timing of
transmissions and equipment across the entire network
SONET
It defines the hierarchy of signals called synchronous transport signals (STS)
Optical carrier (OC) levels are the implementation of STS
SONETSDH Rates
STS OC Rate (Mbps) STM
STS-1 OC-1 5184
STS-3 OC-3 15552 STM-1
STS-9 OC-9 46656 STM-3
STS-12 OC-12 62208 STM-4
STS-18 OC-18 93312 STM-6
STS-24 OC-24 124416 STM-8
STS-36 OC-36 186623 STM-12
STS-48 OC-48 248832 STM-16
STS-96 OC-96 497664 STM-32
STS-192 OC-192 995328 STM-64
STM-synchronous transport module
SONET Four Layers
1 Photonic layer is the lowest and performs physical layer activities
A frame at the photonic layer for STS-1 consists of 6480 bits (8000 framessec)
2-4 Section Line and Path layers correspond to the OSI modelrsquos datalink layer Eachof these layers is responsible for signal transfer across a specific portion of the
1 STS multiplexer combines several optical signals to make an STS signal2 Regenerator removes noise from optical signal
3 Adddrop multiplexer adds STS signals from different paths and removes STS signal
from a path
XTCPIP
Transmission Control ProtocolInternetworking Protocol (TCPIP)
Is a set of rules and procedures that governs the exchange of messages in an
internetwork Originally developed as a protocol for networks that wanted to be connected to
ARPANET a US Department of Defense project now known as Internet
Is a five-layer protocol suite whose bottom four layers match the OSI model fairly
closely The highest level the application layer corresponds to OSIrsquos top threelayers
Internet Protocol (IP) Is defined at the network layer
Unreliable and connectionless Is basically the set of rules for one network communicating with any other To be part of internet organization needs an internet network number unique
number to be included in any packet sent out of the network onto the internet
IP packet is known as datagram consists of a variable header and a variable data
field
IP Address
Uniquely defines the connection of a host to its network The host with more than
one IP address is multi-homed host
IP Addressing
32 bit binary number usually represented as 4 decimal values Equivalent to 4 octets ( 8 bits each decimal value ) Dotted decimal notation Consists of 2 parts the network and the node
Network ndash identifier of particular network on the internet
Host ndash identifier of a particular device which can be a server or a
LAN Access Methodrarr it is unnecessary to have a MAC in pt-to-pt full duplex because there are
only two devices on the circuit and full duplex permits either device to
transmit at any time
rarr if it is point-to-point half duplex it needs MAC and also in multipoint full
duplex configurations since several devices share the same channelrarr to ensure that no two devices attempt to transmit data at the same time
1 Controlled Access
a X-on X-off
rarrthe oldest media access control protocols dating back to the days of theteletype
b Polling
rarr the process of sending signal to a terminal to transmit or asking it to receive
rarr it uses ldquoroll call pollingrdquo with scheme or sequence
Node 3its your time to transmitNode 1 its your turn to sendNode 4 you can transmit after node 1
c Token Passing
rarrA channel accessing arrangement that is best suited for ring topology witheither a baseband or broadband network It uses a token and the token circulate in
the network
Token is an electrical signal that circulate around the ring network from onestation to another If the station has the token it can send a message
2 Contention
rarr opposite of controlled access
rarr devices wait until the circuit is free and transmit whenever it has data to send
a Carrier Sense Multiple Access with Collision Detection (CSMACD)
rarrA channel accessing method a node monitors the line to determine if the line is
busy If the station has a message to transmit but the line is busy it waits for an
idle condition before it transmits its message
Collision is the situation when two nodes transmit simultaneously using one link
Backoff Time is the ceasing time before the station attempts to transmit again
Is the process where computers on a token-ring network detect a problem and
attempt to fix it
FDDI (Fiber Distributed Data Interface)
Uses fiber-optic cable and token-passing to create a very fast reliable networkoperating at speeds of 100 Mbps
It includes up to 500 nodes over a distance of 100 km It uses ring topology with two counter-rotating rings It is implement as true physical ring topology A break in a FDDI network results in packets being sent back on the second ring
1 End system (ES) is a network device that does not perform routing or other traffic
forwarding functions Typical ESs include such devices as terminals PCs and printers
2 Intermediate System (IS) is a network device that performs routing or other traffic-forwarding functions it includes devices such as routers switches and bridges
Intradomain IS communicates within a single autonomous system Interdomain IS communicates within and between autonomous systems
3 Area is a logical group of network segments and their attached devices Areas aresubdivisions of autonomous systems
4 Autonomous System (AS) is a collection of networks under a common administrationthat share a common routing strategy Autonomous system are subdivided into areas and
It involves three phases connection establishment- a single path between the
source and the destination systems is determined data transfer ndash transmitted sequentially
over the path that has been established and connection termination ndash termination of paththat has been establish
Connectionless
Offers two important advantages over connection-oriented service dynamic path
selection ndash enables traffic to be routed around network failures because paths are selectedon a packet-to-packet basis dynamic bandwidth allocation ndash used more efficiently
because network resources are not allocated a bandwidth that they will not use
Virtual Circuits
Switched Virtual CircuitA virtual circuit that is dynamically established on demand and terminated when
transmission is completed It has three phases circuit establishment data transfer and
circuit termination
Permanent Virtual Circuit
A permanently established virtual circuit consists of one mode the data transfer
Internetworking Devices
Hubs
bull A hub is a central network device that connects network devices in a startopology
bull Advanced hubs provide very high speed connectivity for FDDI Fast Ethernet
frame relay and ATM networks
bull It is also referred to as a concentrator (or switch) which is a device that can
have multiple inputs and outputs all active at a one time
bull Services offered by hubs
bull Provide a central unit from which to connect multiple nodes into one network
bull Permit large numbers of computers to be connected on single or multipleLANs
bull Reduce network congestion through centralizing network design
bull Provide multiprotocol services such as Ethernet-to-FDDI connectivity
bull Consolidate the network backbone
bull Enable high-speed communications
bull Provide connections for several different media types
bull Multiplexers are network devices that can receive multiple inputs and transmit
them to a shared network medium
bull A multiplexer is a switch that divides a communication medium into multiple
channels so several nodes can communicate at the same time
bull A signal that is multiplexed must be demultiplexed at the other endbull Multiplexers simply are switches used in old and new technology such as the
following
Telephone switching
Switching telecommunications lines to create multiple channels on a
single line Serial communications to enable more than one terminal to
communicate over a single line Fast Ethernet X25 ISDN frame relay ATM and other networking
technologies to create multiple communication channels over a single
communications cable
bull Work at the OSI physical level switching from channel to channel using one
of three physical methods
bull Time division multiplexing (TDM)
bull Frequency division multiplexing (FDM)
bull Wavelength division multiplexing (WDM)
Bridges
A bridge is a network device that connects different LAN segments using the same accessmethod
Bridges are used to
bull To extend a LAN when the maximum connections limit has been reached
bull To extend a LAN beyond the length limit
bull To segment LANs to reduce data traffic bottlenecks
bull To prevent unauthorized access to LAN (for security)
Standby indicator Pin 36 provides the confirmation signal from the DCE in response to
select standby (pin 32)
Send common Pin 37 provides a common signal return line for unbalanced circuits from
the DTE to the DCE
Electrical Specifications
bull EIA 449 uses two other standards to define its electrical specifications
RS-423 (for unbalanced circuits) and RS-422 (for balanced circuits)
RS-423 Unbalanced Mode
bull An unbalanced circuit specification meaning that it defines only one linefor propagating a signal All signals in this standard use a common return
(or ground) to complete the circuit
RS-422 Balanced Mode
bull A balanced circuit specification meaning that it defines two lines for the propagation of each signal Signals again use a common return (or ground)
for the return of the signal In balanced mode EIA-449 utilizes both pinsin each Category I but does not use the Category II pins The ratio of data
rate to distance is much higher that that of the unbalanced standard or of
EIA-232 10 Mbps for transmission of 40 feet bull In balanced mode two lines carry the same transmission it do not carry
identical signals The signal on one line is the complement of the signal
on the other When plotted the complement looks like a mirror image ofthe original signal Instead of listening to either actual signal the receiver
detects the differences between the two This mechanism makes a balanced circuit less susceptible to noise than an unbalanced circuit and
improves performance
EIA-530
bull A version of EIA-449 that uses DB-25 pins
bull The pin functions of EIA-530 are essentially the same of EIA-449
Category I plus three pins from Category II (the loopback circuits) Other pins in EIA-232 are omitted in EIA-530 such as ring indicator signal
quality detector and data signal rate selector
X21
bull Is an interface standard designed by ITU-T to address many problems
existing in the EIA interfaces and at the same time paves the way for alldigital communications
bull A large proportion of the circuits in the EIA interfaces are used forcontrol since these are necessary to implement control functions as
separate signals With a separate line control information is represented
only by positive and negative voltages But if control signals are encoded
using a meaningful control characters from a system such as ASCII it can be transmitted over data lines
bull X21 eliminates most of the control circuits of the EIA standards and
instead directs its traffic over the data circuits To make this consolidationof functionality possible both the DTE and the DCE must have added
circuit logic that enables them to transform the control codes into bit
streams that can be sent over the data line Both also need additional logicto discriminate between control information and data upon receipt
bull Design of X21 allows not only to use fewer pins but also to be used in
digital telecommunications where control information is sent from deviceto device over a network rather than just between a DTE and a DCE
bull X21 is useful both as an interface to connect digital computers to analogdevices such as modems and as a connector between digital computers and
digital interfaces such as ISDN and X25
Byte Timing
bull Another advantage offered by X21 is that of timing lines to control bytesynchronization in addition to the bit synchronization provided by the EIA
standards By adding a byte timing pulse improves the overall
synchronization of transmissions
Control and indication
bull Pins 3 and 5 of the DB-15 connector are used for the initial handshake or
agreement to begin transmitting Pin 3 is the equivalent of request to send
Pin 5 is the equivalent of clear to send
MODEMbull Modem stands for modulatordemodulator
bull A modulator converts a digital to an analog signalbull A demodulator converts an analog signal to a digital signal
bull The series of 1s and 0s are transformed through the mechanism of ASK
FSK PSK and QAM
Transmission Rate
Bandwidth
bull Every line has upper limit and a lower limit on the frequencies of the
signals it carry this limited range is called the bandwidth
It handles connection establishment and termination data transfer
and packet creation protocols Two types of PLP packets information and control
Up to 4096 channels may be multiplexed at the PLP level Specifies protocols to handle resizing of messages
FRAME RELAY LAYERSbull A technology that operates only at the physical and datalink layers No protocol is
specified for the physical layer the choice is up to the user
bull Eliminates the extensive error checking necessary in X25 protocol
bull It uses simplified version of HDLC protocol in the datalink layerbull It uses routing and switching functions of the datalink layers Frames not packets
are switched
bull It uses PVCs (permanent virtual circuits) Identified through a DLCI (dalta linkconnection identifier)
bull A switch in frame relay performs error checking and routing Error correction is
left to the other protocols at the higher layers
bull Flow control is handled through setting the BECN (backwards explicit congestionnotification) and FECN (forward explicit congestion notification) in the address
field of the frame
bull
ASYNCHRONOUS TRANSFER MODE (ATM)
bull Is the cell relay protocol designed by the ATM forum and adopted by theITU-T
bull In ATM some software functions have moved to hardware this can
increase the data rate
Terms
Cell is the data packet is called a and is composed of 53 bytes (5 bytes of header and 48 bytes of payload) Because each cell is the same size and all are relatively small delay
and other problems associated with multiplexing different sized packets are avoided
A cell network is based on permanent virtual circuit (PVC) routing
bull Virtual Path Identifier (VPI) specifies the path a cell should take
1 Virtual path (VP) switching ndash channels within each VP remain with the VP
2 Virtual path and channel (VPC) switching ndash a channel from one VP may pass into
another VP
IXSDHSONET
Synchronous Optical Network (SONET)
Developed by ANSI
Synchronous Digital Hierarchy (SDH)
Developed by ITU-T
SONETSDH
The two are nearly identical ANSI and ITU-T defined standards that arefundamentally similar and ultimately compatible
Is a synchronous network a single clock is used to handle the timing of
transmissions and equipment across the entire network
SONET
It defines the hierarchy of signals called synchronous transport signals (STS)
Optical carrier (OC) levels are the implementation of STS
SONETSDH Rates
STS OC Rate (Mbps) STM
STS-1 OC-1 5184
STS-3 OC-3 15552 STM-1
STS-9 OC-9 46656 STM-3
STS-12 OC-12 62208 STM-4
STS-18 OC-18 93312 STM-6
STS-24 OC-24 124416 STM-8
STS-36 OC-36 186623 STM-12
STS-48 OC-48 248832 STM-16
STS-96 OC-96 497664 STM-32
STS-192 OC-192 995328 STM-64
STM-synchronous transport module
SONET Four Layers
1 Photonic layer is the lowest and performs physical layer activities
A frame at the photonic layer for STS-1 consists of 6480 bits (8000 framessec)
2-4 Section Line and Path layers correspond to the OSI modelrsquos datalink layer Eachof these layers is responsible for signal transfer across a specific portion of the
1 STS multiplexer combines several optical signals to make an STS signal2 Regenerator removes noise from optical signal
3 Adddrop multiplexer adds STS signals from different paths and removes STS signal
from a path
XTCPIP
Transmission Control ProtocolInternetworking Protocol (TCPIP)
Is a set of rules and procedures that governs the exchange of messages in an
internetwork Originally developed as a protocol for networks that wanted to be connected to
ARPANET a US Department of Defense project now known as Internet
Is a five-layer protocol suite whose bottom four layers match the OSI model fairly
closely The highest level the application layer corresponds to OSIrsquos top threelayers
Internet Protocol (IP) Is defined at the network layer
Unreliable and connectionless Is basically the set of rules for one network communicating with any other To be part of internet organization needs an internet network number unique
number to be included in any packet sent out of the network onto the internet
IP packet is known as datagram consists of a variable header and a variable data
field
IP Address
Uniquely defines the connection of a host to its network The host with more than
one IP address is multi-homed host
IP Addressing
32 bit binary number usually represented as 4 decimal values Equivalent to 4 octets ( 8 bits each decimal value ) Dotted decimal notation Consists of 2 parts the network and the node
Network ndash identifier of particular network on the internet
Host ndash identifier of a particular device which can be a server or a
Is the process where computers on a token-ring network detect a problem and
attempt to fix it
FDDI (Fiber Distributed Data Interface)
Uses fiber-optic cable and token-passing to create a very fast reliable networkoperating at speeds of 100 Mbps
It includes up to 500 nodes over a distance of 100 km It uses ring topology with two counter-rotating rings It is implement as true physical ring topology A break in a FDDI network results in packets being sent back on the second ring
1 End system (ES) is a network device that does not perform routing or other traffic
forwarding functions Typical ESs include such devices as terminals PCs and printers
2 Intermediate System (IS) is a network device that performs routing or other traffic-forwarding functions it includes devices such as routers switches and bridges
Intradomain IS communicates within a single autonomous system Interdomain IS communicates within and between autonomous systems
3 Area is a logical group of network segments and their attached devices Areas aresubdivisions of autonomous systems
4 Autonomous System (AS) is a collection of networks under a common administrationthat share a common routing strategy Autonomous system are subdivided into areas and
It involves three phases connection establishment- a single path between the
source and the destination systems is determined data transfer ndash transmitted sequentially
over the path that has been established and connection termination ndash termination of paththat has been establish
Connectionless
Offers two important advantages over connection-oriented service dynamic path
selection ndash enables traffic to be routed around network failures because paths are selectedon a packet-to-packet basis dynamic bandwidth allocation ndash used more efficiently
because network resources are not allocated a bandwidth that they will not use
Virtual Circuits
Switched Virtual CircuitA virtual circuit that is dynamically established on demand and terminated when
transmission is completed It has three phases circuit establishment data transfer and
circuit termination
Permanent Virtual Circuit
A permanently established virtual circuit consists of one mode the data transfer
Internetworking Devices
Hubs
bull A hub is a central network device that connects network devices in a startopology
bull Advanced hubs provide very high speed connectivity for FDDI Fast Ethernet
frame relay and ATM networks
bull It is also referred to as a concentrator (or switch) which is a device that can
have multiple inputs and outputs all active at a one time
bull Services offered by hubs
bull Provide a central unit from which to connect multiple nodes into one network
bull Permit large numbers of computers to be connected on single or multipleLANs
bull Reduce network congestion through centralizing network design
bull Provide multiprotocol services such as Ethernet-to-FDDI connectivity
bull Consolidate the network backbone
bull Enable high-speed communications
bull Provide connections for several different media types
bull Multiplexers are network devices that can receive multiple inputs and transmit
them to a shared network medium
bull A multiplexer is a switch that divides a communication medium into multiple
channels so several nodes can communicate at the same time
bull A signal that is multiplexed must be demultiplexed at the other endbull Multiplexers simply are switches used in old and new technology such as the
following
Telephone switching
Switching telecommunications lines to create multiple channels on a
single line Serial communications to enable more than one terminal to
communicate over a single line Fast Ethernet X25 ISDN frame relay ATM and other networking
technologies to create multiple communication channels over a single
communications cable
bull Work at the OSI physical level switching from channel to channel using one
of three physical methods
bull Time division multiplexing (TDM)
bull Frequency division multiplexing (FDM)
bull Wavelength division multiplexing (WDM)
Bridges
A bridge is a network device that connects different LAN segments using the same accessmethod
Bridges are used to
bull To extend a LAN when the maximum connections limit has been reached
bull To extend a LAN beyond the length limit
bull To segment LANs to reduce data traffic bottlenecks
bull To prevent unauthorized access to LAN (for security)
Standby indicator Pin 36 provides the confirmation signal from the DCE in response to
select standby (pin 32)
Send common Pin 37 provides a common signal return line for unbalanced circuits from
the DTE to the DCE
Electrical Specifications
bull EIA 449 uses two other standards to define its electrical specifications
RS-423 (for unbalanced circuits) and RS-422 (for balanced circuits)
RS-423 Unbalanced Mode
bull An unbalanced circuit specification meaning that it defines only one linefor propagating a signal All signals in this standard use a common return
(or ground) to complete the circuit
RS-422 Balanced Mode
bull A balanced circuit specification meaning that it defines two lines for the propagation of each signal Signals again use a common return (or ground)
for the return of the signal In balanced mode EIA-449 utilizes both pinsin each Category I but does not use the Category II pins The ratio of data
rate to distance is much higher that that of the unbalanced standard or of
EIA-232 10 Mbps for transmission of 40 feet bull In balanced mode two lines carry the same transmission it do not carry
identical signals The signal on one line is the complement of the signal
on the other When plotted the complement looks like a mirror image ofthe original signal Instead of listening to either actual signal the receiver
detects the differences between the two This mechanism makes a balanced circuit less susceptible to noise than an unbalanced circuit and
improves performance
EIA-530
bull A version of EIA-449 that uses DB-25 pins
bull The pin functions of EIA-530 are essentially the same of EIA-449
Category I plus three pins from Category II (the loopback circuits) Other pins in EIA-232 are omitted in EIA-530 such as ring indicator signal
quality detector and data signal rate selector
X21
bull Is an interface standard designed by ITU-T to address many problems
existing in the EIA interfaces and at the same time paves the way for alldigital communications
bull A large proportion of the circuits in the EIA interfaces are used forcontrol since these are necessary to implement control functions as
separate signals With a separate line control information is represented
only by positive and negative voltages But if control signals are encoded
using a meaningful control characters from a system such as ASCII it can be transmitted over data lines
bull X21 eliminates most of the control circuits of the EIA standards and
instead directs its traffic over the data circuits To make this consolidationof functionality possible both the DTE and the DCE must have added
circuit logic that enables them to transform the control codes into bit
streams that can be sent over the data line Both also need additional logicto discriminate between control information and data upon receipt
bull Design of X21 allows not only to use fewer pins but also to be used in
digital telecommunications where control information is sent from deviceto device over a network rather than just between a DTE and a DCE
bull X21 is useful both as an interface to connect digital computers to analogdevices such as modems and as a connector between digital computers and
digital interfaces such as ISDN and X25
Byte Timing
bull Another advantage offered by X21 is that of timing lines to control bytesynchronization in addition to the bit synchronization provided by the EIA
standards By adding a byte timing pulse improves the overall
synchronization of transmissions
Control and indication
bull Pins 3 and 5 of the DB-15 connector are used for the initial handshake or
agreement to begin transmitting Pin 3 is the equivalent of request to send
Pin 5 is the equivalent of clear to send
MODEMbull Modem stands for modulatordemodulator
bull A modulator converts a digital to an analog signalbull A demodulator converts an analog signal to a digital signal
bull The series of 1s and 0s are transformed through the mechanism of ASK
FSK PSK and QAM
Transmission Rate
Bandwidth
bull Every line has upper limit and a lower limit on the frequencies of the
signals it carry this limited range is called the bandwidth
It handles connection establishment and termination data transfer
and packet creation protocols Two types of PLP packets information and control
Up to 4096 channels may be multiplexed at the PLP level Specifies protocols to handle resizing of messages
FRAME RELAY LAYERSbull A technology that operates only at the physical and datalink layers No protocol is
specified for the physical layer the choice is up to the user
bull Eliminates the extensive error checking necessary in X25 protocol
bull It uses simplified version of HDLC protocol in the datalink layerbull It uses routing and switching functions of the datalink layers Frames not packets
are switched
bull It uses PVCs (permanent virtual circuits) Identified through a DLCI (dalta linkconnection identifier)
bull A switch in frame relay performs error checking and routing Error correction is
left to the other protocols at the higher layers
bull Flow control is handled through setting the BECN (backwards explicit congestionnotification) and FECN (forward explicit congestion notification) in the address
field of the frame
bull
ASYNCHRONOUS TRANSFER MODE (ATM)
bull Is the cell relay protocol designed by the ATM forum and adopted by theITU-T
bull In ATM some software functions have moved to hardware this can
increase the data rate
Terms
Cell is the data packet is called a and is composed of 53 bytes (5 bytes of header and 48 bytes of payload) Because each cell is the same size and all are relatively small delay
and other problems associated with multiplexing different sized packets are avoided
A cell network is based on permanent virtual circuit (PVC) routing
bull Virtual Path Identifier (VPI) specifies the path a cell should take
1 Virtual path (VP) switching ndash channels within each VP remain with the VP
2 Virtual path and channel (VPC) switching ndash a channel from one VP may pass into
another VP
IXSDHSONET
Synchronous Optical Network (SONET)
Developed by ANSI
Synchronous Digital Hierarchy (SDH)
Developed by ITU-T
SONETSDH
The two are nearly identical ANSI and ITU-T defined standards that arefundamentally similar and ultimately compatible
Is a synchronous network a single clock is used to handle the timing of
transmissions and equipment across the entire network
SONET
It defines the hierarchy of signals called synchronous transport signals (STS)
Optical carrier (OC) levels are the implementation of STS
SONETSDH Rates
STS OC Rate (Mbps) STM
STS-1 OC-1 5184
STS-3 OC-3 15552 STM-1
STS-9 OC-9 46656 STM-3
STS-12 OC-12 62208 STM-4
STS-18 OC-18 93312 STM-6
STS-24 OC-24 124416 STM-8
STS-36 OC-36 186623 STM-12
STS-48 OC-48 248832 STM-16
STS-96 OC-96 497664 STM-32
STS-192 OC-192 995328 STM-64
STM-synchronous transport module
SONET Four Layers
1 Photonic layer is the lowest and performs physical layer activities
A frame at the photonic layer for STS-1 consists of 6480 bits (8000 framessec)
2-4 Section Line and Path layers correspond to the OSI modelrsquos datalink layer Eachof these layers is responsible for signal transfer across a specific portion of the
1 STS multiplexer combines several optical signals to make an STS signal2 Regenerator removes noise from optical signal
3 Adddrop multiplexer adds STS signals from different paths and removes STS signal
from a path
XTCPIP
Transmission Control ProtocolInternetworking Protocol (TCPIP)
Is a set of rules and procedures that governs the exchange of messages in an
internetwork Originally developed as a protocol for networks that wanted to be connected to
ARPANET a US Department of Defense project now known as Internet
Is a five-layer protocol suite whose bottom four layers match the OSI model fairly
closely The highest level the application layer corresponds to OSIrsquos top threelayers
Internet Protocol (IP) Is defined at the network layer
Unreliable and connectionless Is basically the set of rules for one network communicating with any other To be part of internet organization needs an internet network number unique
number to be included in any packet sent out of the network onto the internet
IP packet is known as datagram consists of a variable header and a variable data
field
IP Address
Uniquely defines the connection of a host to its network The host with more than
one IP address is multi-homed host
IP Addressing
32 bit binary number usually represented as 4 decimal values Equivalent to 4 octets ( 8 bits each decimal value ) Dotted decimal notation Consists of 2 parts the network and the node
Network ndash identifier of particular network on the internet
Host ndash identifier of a particular device which can be a server or a
Is the process where computers on a token-ring network detect a problem and
attempt to fix it
FDDI (Fiber Distributed Data Interface)
Uses fiber-optic cable and token-passing to create a very fast reliable networkoperating at speeds of 100 Mbps
It includes up to 500 nodes over a distance of 100 km It uses ring topology with two counter-rotating rings It is implement as true physical ring topology A break in a FDDI network results in packets being sent back on the second ring
1 End system (ES) is a network device that does not perform routing or other traffic
forwarding functions Typical ESs include such devices as terminals PCs and printers
2 Intermediate System (IS) is a network device that performs routing or other traffic-forwarding functions it includes devices such as routers switches and bridges
Intradomain IS communicates within a single autonomous system Interdomain IS communicates within and between autonomous systems
3 Area is a logical group of network segments and their attached devices Areas aresubdivisions of autonomous systems
4 Autonomous System (AS) is a collection of networks under a common administrationthat share a common routing strategy Autonomous system are subdivided into areas and
It involves three phases connection establishment- a single path between the
source and the destination systems is determined data transfer ndash transmitted sequentially
over the path that has been established and connection termination ndash termination of paththat has been establish
Connectionless
Offers two important advantages over connection-oriented service dynamic path
selection ndash enables traffic to be routed around network failures because paths are selectedon a packet-to-packet basis dynamic bandwidth allocation ndash used more efficiently
because network resources are not allocated a bandwidth that they will not use
Virtual Circuits
Switched Virtual CircuitA virtual circuit that is dynamically established on demand and terminated when
transmission is completed It has three phases circuit establishment data transfer and
circuit termination
Permanent Virtual Circuit
A permanently established virtual circuit consists of one mode the data transfer
Internetworking Devices
Hubs
bull A hub is a central network device that connects network devices in a startopology
bull Advanced hubs provide very high speed connectivity for FDDI Fast Ethernet
frame relay and ATM networks
bull It is also referred to as a concentrator (or switch) which is a device that can
have multiple inputs and outputs all active at a one time
bull Services offered by hubs
bull Provide a central unit from which to connect multiple nodes into one network
bull Permit large numbers of computers to be connected on single or multipleLANs
bull Reduce network congestion through centralizing network design
bull Provide multiprotocol services such as Ethernet-to-FDDI connectivity
bull Consolidate the network backbone
bull Enable high-speed communications
bull Provide connections for several different media types
bull Multiplexers are network devices that can receive multiple inputs and transmit
them to a shared network medium
bull A multiplexer is a switch that divides a communication medium into multiple
channels so several nodes can communicate at the same time
bull A signal that is multiplexed must be demultiplexed at the other endbull Multiplexers simply are switches used in old and new technology such as the
following
Telephone switching
Switching telecommunications lines to create multiple channels on a
single line Serial communications to enable more than one terminal to
communicate over a single line Fast Ethernet X25 ISDN frame relay ATM and other networking
technologies to create multiple communication channels over a single
communications cable
bull Work at the OSI physical level switching from channel to channel using one
of three physical methods
bull Time division multiplexing (TDM)
bull Frequency division multiplexing (FDM)
bull Wavelength division multiplexing (WDM)
Bridges
A bridge is a network device that connects different LAN segments using the same accessmethod
Bridges are used to
bull To extend a LAN when the maximum connections limit has been reached
bull To extend a LAN beyond the length limit
bull To segment LANs to reduce data traffic bottlenecks
bull To prevent unauthorized access to LAN (for security)
Standby indicator Pin 36 provides the confirmation signal from the DCE in response to
select standby (pin 32)
Send common Pin 37 provides a common signal return line for unbalanced circuits from
the DTE to the DCE
Electrical Specifications
bull EIA 449 uses two other standards to define its electrical specifications
RS-423 (for unbalanced circuits) and RS-422 (for balanced circuits)
RS-423 Unbalanced Mode
bull An unbalanced circuit specification meaning that it defines only one linefor propagating a signal All signals in this standard use a common return
(or ground) to complete the circuit
RS-422 Balanced Mode
bull A balanced circuit specification meaning that it defines two lines for the propagation of each signal Signals again use a common return (or ground)
for the return of the signal In balanced mode EIA-449 utilizes both pinsin each Category I but does not use the Category II pins The ratio of data
rate to distance is much higher that that of the unbalanced standard or of
EIA-232 10 Mbps for transmission of 40 feet bull In balanced mode two lines carry the same transmission it do not carry
identical signals The signal on one line is the complement of the signal
on the other When plotted the complement looks like a mirror image ofthe original signal Instead of listening to either actual signal the receiver
detects the differences between the two This mechanism makes a balanced circuit less susceptible to noise than an unbalanced circuit and
improves performance
EIA-530
bull A version of EIA-449 that uses DB-25 pins
bull The pin functions of EIA-530 are essentially the same of EIA-449
Category I plus three pins from Category II (the loopback circuits) Other pins in EIA-232 are omitted in EIA-530 such as ring indicator signal
quality detector and data signal rate selector
X21
bull Is an interface standard designed by ITU-T to address many problems
existing in the EIA interfaces and at the same time paves the way for alldigital communications
bull A large proportion of the circuits in the EIA interfaces are used forcontrol since these are necessary to implement control functions as
separate signals With a separate line control information is represented
only by positive and negative voltages But if control signals are encoded
using a meaningful control characters from a system such as ASCII it can be transmitted over data lines
bull X21 eliminates most of the control circuits of the EIA standards and
instead directs its traffic over the data circuits To make this consolidationof functionality possible both the DTE and the DCE must have added
circuit logic that enables them to transform the control codes into bit
streams that can be sent over the data line Both also need additional logicto discriminate between control information and data upon receipt
bull Design of X21 allows not only to use fewer pins but also to be used in
digital telecommunications where control information is sent from deviceto device over a network rather than just between a DTE and a DCE
bull X21 is useful both as an interface to connect digital computers to analogdevices such as modems and as a connector between digital computers and
digital interfaces such as ISDN and X25
Byte Timing
bull Another advantage offered by X21 is that of timing lines to control bytesynchronization in addition to the bit synchronization provided by the EIA
standards By adding a byte timing pulse improves the overall
synchronization of transmissions
Control and indication
bull Pins 3 and 5 of the DB-15 connector are used for the initial handshake or
agreement to begin transmitting Pin 3 is the equivalent of request to send
Pin 5 is the equivalent of clear to send
MODEMbull Modem stands for modulatordemodulator
bull A modulator converts a digital to an analog signalbull A demodulator converts an analog signal to a digital signal
bull The series of 1s and 0s are transformed through the mechanism of ASK
FSK PSK and QAM
Transmission Rate
Bandwidth
bull Every line has upper limit and a lower limit on the frequencies of the
signals it carry this limited range is called the bandwidth
It handles connection establishment and termination data transfer
and packet creation protocols Two types of PLP packets information and control
Up to 4096 channels may be multiplexed at the PLP level Specifies protocols to handle resizing of messages
FRAME RELAY LAYERSbull A technology that operates only at the physical and datalink layers No protocol is
specified for the physical layer the choice is up to the user
bull Eliminates the extensive error checking necessary in X25 protocol
bull It uses simplified version of HDLC protocol in the datalink layerbull It uses routing and switching functions of the datalink layers Frames not packets
are switched
bull It uses PVCs (permanent virtual circuits) Identified through a DLCI (dalta linkconnection identifier)
bull A switch in frame relay performs error checking and routing Error correction is
left to the other protocols at the higher layers
bull Flow control is handled through setting the BECN (backwards explicit congestionnotification) and FECN (forward explicit congestion notification) in the address
field of the frame
bull
ASYNCHRONOUS TRANSFER MODE (ATM)
bull Is the cell relay protocol designed by the ATM forum and adopted by theITU-T
bull In ATM some software functions have moved to hardware this can
increase the data rate
Terms
Cell is the data packet is called a and is composed of 53 bytes (5 bytes of header and 48 bytes of payload) Because each cell is the same size and all are relatively small delay
and other problems associated with multiplexing different sized packets are avoided
A cell network is based on permanent virtual circuit (PVC) routing
bull Virtual Path Identifier (VPI) specifies the path a cell should take
1 Virtual path (VP) switching ndash channels within each VP remain with the VP
2 Virtual path and channel (VPC) switching ndash a channel from one VP may pass into
another VP
IXSDHSONET
Synchronous Optical Network (SONET)
Developed by ANSI
Synchronous Digital Hierarchy (SDH)
Developed by ITU-T
SONETSDH
The two are nearly identical ANSI and ITU-T defined standards that arefundamentally similar and ultimately compatible
Is a synchronous network a single clock is used to handle the timing of
transmissions and equipment across the entire network
SONET
It defines the hierarchy of signals called synchronous transport signals (STS)
Optical carrier (OC) levels are the implementation of STS
SONETSDH Rates
STS OC Rate (Mbps) STM
STS-1 OC-1 5184
STS-3 OC-3 15552 STM-1
STS-9 OC-9 46656 STM-3
STS-12 OC-12 62208 STM-4
STS-18 OC-18 93312 STM-6
STS-24 OC-24 124416 STM-8
STS-36 OC-36 186623 STM-12
STS-48 OC-48 248832 STM-16
STS-96 OC-96 497664 STM-32
STS-192 OC-192 995328 STM-64
STM-synchronous transport module
SONET Four Layers
1 Photonic layer is the lowest and performs physical layer activities
A frame at the photonic layer for STS-1 consists of 6480 bits (8000 framessec)
2-4 Section Line and Path layers correspond to the OSI modelrsquos datalink layer Eachof these layers is responsible for signal transfer across a specific portion of the
1 STS multiplexer combines several optical signals to make an STS signal2 Regenerator removes noise from optical signal
3 Adddrop multiplexer adds STS signals from different paths and removes STS signal
from a path
XTCPIP
Transmission Control ProtocolInternetworking Protocol (TCPIP)
Is a set of rules and procedures that governs the exchange of messages in an
internetwork Originally developed as a protocol for networks that wanted to be connected to
ARPANET a US Department of Defense project now known as Internet
Is a five-layer protocol suite whose bottom four layers match the OSI model fairly
closely The highest level the application layer corresponds to OSIrsquos top threelayers
Internet Protocol (IP) Is defined at the network layer
Unreliable and connectionless Is basically the set of rules for one network communicating with any other To be part of internet organization needs an internet network number unique
number to be included in any packet sent out of the network onto the internet
IP packet is known as datagram consists of a variable header and a variable data
field
IP Address
Uniquely defines the connection of a host to its network The host with more than
one IP address is multi-homed host
IP Addressing
32 bit binary number usually represented as 4 decimal values Equivalent to 4 octets ( 8 bits each decimal value ) Dotted decimal notation Consists of 2 parts the network and the node
Network ndash identifier of particular network on the internet
Host ndash identifier of a particular device which can be a server or a
Is the process where computers on a token-ring network detect a problem and
attempt to fix it
FDDI (Fiber Distributed Data Interface)
Uses fiber-optic cable and token-passing to create a very fast reliable networkoperating at speeds of 100 Mbps
It includes up to 500 nodes over a distance of 100 km It uses ring topology with two counter-rotating rings It is implement as true physical ring topology A break in a FDDI network results in packets being sent back on the second ring
1 End system (ES) is a network device that does not perform routing or other traffic
forwarding functions Typical ESs include such devices as terminals PCs and printers
2 Intermediate System (IS) is a network device that performs routing or other traffic-forwarding functions it includes devices such as routers switches and bridges
Intradomain IS communicates within a single autonomous system Interdomain IS communicates within and between autonomous systems
3 Area is a logical group of network segments and their attached devices Areas aresubdivisions of autonomous systems
4 Autonomous System (AS) is a collection of networks under a common administrationthat share a common routing strategy Autonomous system are subdivided into areas and
It involves three phases connection establishment- a single path between the
source and the destination systems is determined data transfer ndash transmitted sequentially
over the path that has been established and connection termination ndash termination of paththat has been establish
Connectionless
Offers two important advantages over connection-oriented service dynamic path
selection ndash enables traffic to be routed around network failures because paths are selectedon a packet-to-packet basis dynamic bandwidth allocation ndash used more efficiently
because network resources are not allocated a bandwidth that they will not use
Virtual Circuits
Switched Virtual CircuitA virtual circuit that is dynamically established on demand and terminated when
transmission is completed It has three phases circuit establishment data transfer and
circuit termination
Permanent Virtual Circuit
A permanently established virtual circuit consists of one mode the data transfer
Internetworking Devices
Hubs
bull A hub is a central network device that connects network devices in a startopology
bull Advanced hubs provide very high speed connectivity for FDDI Fast Ethernet
frame relay and ATM networks
bull It is also referred to as a concentrator (or switch) which is a device that can
have multiple inputs and outputs all active at a one time
bull Services offered by hubs
bull Provide a central unit from which to connect multiple nodes into one network
bull Permit large numbers of computers to be connected on single or multipleLANs
bull Reduce network congestion through centralizing network design
bull Provide multiprotocol services such as Ethernet-to-FDDI connectivity
bull Consolidate the network backbone
bull Enable high-speed communications
bull Provide connections for several different media types
bull Multiplexers are network devices that can receive multiple inputs and transmit
them to a shared network medium
bull A multiplexer is a switch that divides a communication medium into multiple
channels so several nodes can communicate at the same time
bull A signal that is multiplexed must be demultiplexed at the other endbull Multiplexers simply are switches used in old and new technology such as the
following
Telephone switching
Switching telecommunications lines to create multiple channels on a
single line Serial communications to enable more than one terminal to
communicate over a single line Fast Ethernet X25 ISDN frame relay ATM and other networking
technologies to create multiple communication channels over a single
communications cable
bull Work at the OSI physical level switching from channel to channel using one
of three physical methods
bull Time division multiplexing (TDM)
bull Frequency division multiplexing (FDM)
bull Wavelength division multiplexing (WDM)
Bridges
A bridge is a network device that connects different LAN segments using the same accessmethod
Bridges are used to
bull To extend a LAN when the maximum connections limit has been reached
bull To extend a LAN beyond the length limit
bull To segment LANs to reduce data traffic bottlenecks
bull To prevent unauthorized access to LAN (for security)
Standby indicator Pin 36 provides the confirmation signal from the DCE in response to
select standby (pin 32)
Send common Pin 37 provides a common signal return line for unbalanced circuits from
the DTE to the DCE
Electrical Specifications
bull EIA 449 uses two other standards to define its electrical specifications
RS-423 (for unbalanced circuits) and RS-422 (for balanced circuits)
RS-423 Unbalanced Mode
bull An unbalanced circuit specification meaning that it defines only one linefor propagating a signal All signals in this standard use a common return
(or ground) to complete the circuit
RS-422 Balanced Mode
bull A balanced circuit specification meaning that it defines two lines for the propagation of each signal Signals again use a common return (or ground)
for the return of the signal In balanced mode EIA-449 utilizes both pinsin each Category I but does not use the Category II pins The ratio of data
rate to distance is much higher that that of the unbalanced standard or of
EIA-232 10 Mbps for transmission of 40 feet bull In balanced mode two lines carry the same transmission it do not carry
identical signals The signal on one line is the complement of the signal
on the other When plotted the complement looks like a mirror image ofthe original signal Instead of listening to either actual signal the receiver
detects the differences between the two This mechanism makes a balanced circuit less susceptible to noise than an unbalanced circuit and
improves performance
EIA-530
bull A version of EIA-449 that uses DB-25 pins
bull The pin functions of EIA-530 are essentially the same of EIA-449
Category I plus three pins from Category II (the loopback circuits) Other pins in EIA-232 are omitted in EIA-530 such as ring indicator signal
quality detector and data signal rate selector
X21
bull Is an interface standard designed by ITU-T to address many problems
existing in the EIA interfaces and at the same time paves the way for alldigital communications
bull A large proportion of the circuits in the EIA interfaces are used forcontrol since these are necessary to implement control functions as
separate signals With a separate line control information is represented
only by positive and negative voltages But if control signals are encoded
using a meaningful control characters from a system such as ASCII it can be transmitted over data lines
bull X21 eliminates most of the control circuits of the EIA standards and
instead directs its traffic over the data circuits To make this consolidationof functionality possible both the DTE and the DCE must have added
circuit logic that enables them to transform the control codes into bit
streams that can be sent over the data line Both also need additional logicto discriminate between control information and data upon receipt
bull Design of X21 allows not only to use fewer pins but also to be used in
digital telecommunications where control information is sent from deviceto device over a network rather than just between a DTE and a DCE
bull X21 is useful both as an interface to connect digital computers to analogdevices such as modems and as a connector between digital computers and
digital interfaces such as ISDN and X25
Byte Timing
bull Another advantage offered by X21 is that of timing lines to control bytesynchronization in addition to the bit synchronization provided by the EIA
standards By adding a byte timing pulse improves the overall
synchronization of transmissions
Control and indication
bull Pins 3 and 5 of the DB-15 connector are used for the initial handshake or
agreement to begin transmitting Pin 3 is the equivalent of request to send
Pin 5 is the equivalent of clear to send
MODEMbull Modem stands for modulatordemodulator
bull A modulator converts a digital to an analog signalbull A demodulator converts an analog signal to a digital signal
bull The series of 1s and 0s are transformed through the mechanism of ASK
FSK PSK and QAM
Transmission Rate
Bandwidth
bull Every line has upper limit and a lower limit on the frequencies of the
signals it carry this limited range is called the bandwidth
It handles connection establishment and termination data transfer
and packet creation protocols Two types of PLP packets information and control
Up to 4096 channels may be multiplexed at the PLP level Specifies protocols to handle resizing of messages
FRAME RELAY LAYERSbull A technology that operates only at the physical and datalink layers No protocol is
specified for the physical layer the choice is up to the user
bull Eliminates the extensive error checking necessary in X25 protocol
bull It uses simplified version of HDLC protocol in the datalink layerbull It uses routing and switching functions of the datalink layers Frames not packets
are switched
bull It uses PVCs (permanent virtual circuits) Identified through a DLCI (dalta linkconnection identifier)
bull A switch in frame relay performs error checking and routing Error correction is
left to the other protocols at the higher layers
bull Flow control is handled through setting the BECN (backwards explicit congestionnotification) and FECN (forward explicit congestion notification) in the address
field of the frame
bull
ASYNCHRONOUS TRANSFER MODE (ATM)
bull Is the cell relay protocol designed by the ATM forum and adopted by theITU-T
bull In ATM some software functions have moved to hardware this can
increase the data rate
Terms
Cell is the data packet is called a and is composed of 53 bytes (5 bytes of header and 48 bytes of payload) Because each cell is the same size and all are relatively small delay
and other problems associated with multiplexing different sized packets are avoided
A cell network is based on permanent virtual circuit (PVC) routing
bull Virtual Path Identifier (VPI) specifies the path a cell should take
1 Virtual path (VP) switching ndash channels within each VP remain with the VP
2 Virtual path and channel (VPC) switching ndash a channel from one VP may pass into
another VP
IXSDHSONET
Synchronous Optical Network (SONET)
Developed by ANSI
Synchronous Digital Hierarchy (SDH)
Developed by ITU-T
SONETSDH
The two are nearly identical ANSI and ITU-T defined standards that arefundamentally similar and ultimately compatible
Is a synchronous network a single clock is used to handle the timing of
transmissions and equipment across the entire network
SONET
It defines the hierarchy of signals called synchronous transport signals (STS)
Optical carrier (OC) levels are the implementation of STS
SONETSDH Rates
STS OC Rate (Mbps) STM
STS-1 OC-1 5184
STS-3 OC-3 15552 STM-1
STS-9 OC-9 46656 STM-3
STS-12 OC-12 62208 STM-4
STS-18 OC-18 93312 STM-6
STS-24 OC-24 124416 STM-8
STS-36 OC-36 186623 STM-12
STS-48 OC-48 248832 STM-16
STS-96 OC-96 497664 STM-32
STS-192 OC-192 995328 STM-64
STM-synchronous transport module
SONET Four Layers
1 Photonic layer is the lowest and performs physical layer activities
A frame at the photonic layer for STS-1 consists of 6480 bits (8000 framessec)
2-4 Section Line and Path layers correspond to the OSI modelrsquos datalink layer Eachof these layers is responsible for signal transfer across a specific portion of the
1 STS multiplexer combines several optical signals to make an STS signal2 Regenerator removes noise from optical signal
3 Adddrop multiplexer adds STS signals from different paths and removes STS signal
from a path
XTCPIP
Transmission Control ProtocolInternetworking Protocol (TCPIP)
Is a set of rules and procedures that governs the exchange of messages in an
internetwork Originally developed as a protocol for networks that wanted to be connected to
ARPANET a US Department of Defense project now known as Internet
Is a five-layer protocol suite whose bottom four layers match the OSI model fairly
closely The highest level the application layer corresponds to OSIrsquos top threelayers
Internet Protocol (IP) Is defined at the network layer
Unreliable and connectionless Is basically the set of rules for one network communicating with any other To be part of internet organization needs an internet network number unique
number to be included in any packet sent out of the network onto the internet
IP packet is known as datagram consists of a variable header and a variable data
field
IP Address
Uniquely defines the connection of a host to its network The host with more than
one IP address is multi-homed host
IP Addressing
32 bit binary number usually represented as 4 decimal values Equivalent to 4 octets ( 8 bits each decimal value ) Dotted decimal notation Consists of 2 parts the network and the node
Network ndash identifier of particular network on the internet
Host ndash identifier of a particular device which can be a server or a
Is the process where computers on a token-ring network detect a problem and
attempt to fix it
FDDI (Fiber Distributed Data Interface)
Uses fiber-optic cable and token-passing to create a very fast reliable networkoperating at speeds of 100 Mbps
It includes up to 500 nodes over a distance of 100 km It uses ring topology with two counter-rotating rings It is implement as true physical ring topology A break in a FDDI network results in packets being sent back on the second ring
1 End system (ES) is a network device that does not perform routing or other traffic
forwarding functions Typical ESs include such devices as terminals PCs and printers
2 Intermediate System (IS) is a network device that performs routing or other traffic-forwarding functions it includes devices such as routers switches and bridges
Intradomain IS communicates within a single autonomous system Interdomain IS communicates within and between autonomous systems
3 Area is a logical group of network segments and their attached devices Areas aresubdivisions of autonomous systems
4 Autonomous System (AS) is a collection of networks under a common administrationthat share a common routing strategy Autonomous system are subdivided into areas and
It involves three phases connection establishment- a single path between the
source and the destination systems is determined data transfer ndash transmitted sequentially
over the path that has been established and connection termination ndash termination of paththat has been establish
Connectionless
Offers two important advantages over connection-oriented service dynamic path
selection ndash enables traffic to be routed around network failures because paths are selectedon a packet-to-packet basis dynamic bandwidth allocation ndash used more efficiently
because network resources are not allocated a bandwidth that they will not use
Virtual Circuits
Switched Virtual CircuitA virtual circuit that is dynamically established on demand and terminated when
transmission is completed It has three phases circuit establishment data transfer and
circuit termination
Permanent Virtual Circuit
A permanently established virtual circuit consists of one mode the data transfer
Internetworking Devices
Hubs
bull A hub is a central network device that connects network devices in a startopology
bull Advanced hubs provide very high speed connectivity for FDDI Fast Ethernet
frame relay and ATM networks
bull It is also referred to as a concentrator (or switch) which is a device that can
have multiple inputs and outputs all active at a one time
bull Services offered by hubs
bull Provide a central unit from which to connect multiple nodes into one network
bull Permit large numbers of computers to be connected on single or multipleLANs
bull Reduce network congestion through centralizing network design
bull Provide multiprotocol services such as Ethernet-to-FDDI connectivity
bull Consolidate the network backbone
bull Enable high-speed communications
bull Provide connections for several different media types
bull Multiplexers are network devices that can receive multiple inputs and transmit
them to a shared network medium
bull A multiplexer is a switch that divides a communication medium into multiple
channels so several nodes can communicate at the same time
bull A signal that is multiplexed must be demultiplexed at the other endbull Multiplexers simply are switches used in old and new technology such as the
following
Telephone switching
Switching telecommunications lines to create multiple channels on a
single line Serial communications to enable more than one terminal to
communicate over a single line Fast Ethernet X25 ISDN frame relay ATM and other networking
technologies to create multiple communication channels over a single
communications cable
bull Work at the OSI physical level switching from channel to channel using one
of three physical methods
bull Time division multiplexing (TDM)
bull Frequency division multiplexing (FDM)
bull Wavelength division multiplexing (WDM)
Bridges
A bridge is a network device that connects different LAN segments using the same accessmethod
Bridges are used to
bull To extend a LAN when the maximum connections limit has been reached
bull To extend a LAN beyond the length limit
bull To segment LANs to reduce data traffic bottlenecks
bull To prevent unauthorized access to LAN (for security)
Standby indicator Pin 36 provides the confirmation signal from the DCE in response to
select standby (pin 32)
Send common Pin 37 provides a common signal return line for unbalanced circuits from
the DTE to the DCE
Electrical Specifications
bull EIA 449 uses two other standards to define its electrical specifications
RS-423 (for unbalanced circuits) and RS-422 (for balanced circuits)
RS-423 Unbalanced Mode
bull An unbalanced circuit specification meaning that it defines only one linefor propagating a signal All signals in this standard use a common return
(or ground) to complete the circuit
RS-422 Balanced Mode
bull A balanced circuit specification meaning that it defines two lines for the propagation of each signal Signals again use a common return (or ground)
for the return of the signal In balanced mode EIA-449 utilizes both pinsin each Category I but does not use the Category II pins The ratio of data
rate to distance is much higher that that of the unbalanced standard or of
EIA-232 10 Mbps for transmission of 40 feet bull In balanced mode two lines carry the same transmission it do not carry
identical signals The signal on one line is the complement of the signal
on the other When plotted the complement looks like a mirror image ofthe original signal Instead of listening to either actual signal the receiver
detects the differences between the two This mechanism makes a balanced circuit less susceptible to noise than an unbalanced circuit and
improves performance
EIA-530
bull A version of EIA-449 that uses DB-25 pins
bull The pin functions of EIA-530 are essentially the same of EIA-449
Category I plus three pins from Category II (the loopback circuits) Other pins in EIA-232 are omitted in EIA-530 such as ring indicator signal
quality detector and data signal rate selector
X21
bull Is an interface standard designed by ITU-T to address many problems
existing in the EIA interfaces and at the same time paves the way for alldigital communications
bull A large proportion of the circuits in the EIA interfaces are used forcontrol since these are necessary to implement control functions as
separate signals With a separate line control information is represented
only by positive and negative voltages But if control signals are encoded
using a meaningful control characters from a system such as ASCII it can be transmitted over data lines
bull X21 eliminates most of the control circuits of the EIA standards and
instead directs its traffic over the data circuits To make this consolidationof functionality possible both the DTE and the DCE must have added
circuit logic that enables them to transform the control codes into bit
streams that can be sent over the data line Both also need additional logicto discriminate between control information and data upon receipt
bull Design of X21 allows not only to use fewer pins but also to be used in
digital telecommunications where control information is sent from deviceto device over a network rather than just between a DTE and a DCE
bull X21 is useful both as an interface to connect digital computers to analogdevices such as modems and as a connector between digital computers and
digital interfaces such as ISDN and X25
Byte Timing
bull Another advantage offered by X21 is that of timing lines to control bytesynchronization in addition to the bit synchronization provided by the EIA
standards By adding a byte timing pulse improves the overall
synchronization of transmissions
Control and indication
bull Pins 3 and 5 of the DB-15 connector are used for the initial handshake or
agreement to begin transmitting Pin 3 is the equivalent of request to send
Pin 5 is the equivalent of clear to send
MODEMbull Modem stands for modulatordemodulator
bull A modulator converts a digital to an analog signalbull A demodulator converts an analog signal to a digital signal
bull The series of 1s and 0s are transformed through the mechanism of ASK
FSK PSK and QAM
Transmission Rate
Bandwidth
bull Every line has upper limit and a lower limit on the frequencies of the
signals it carry this limited range is called the bandwidth
It handles connection establishment and termination data transfer
and packet creation protocols Two types of PLP packets information and control
Up to 4096 channels may be multiplexed at the PLP level Specifies protocols to handle resizing of messages
FRAME RELAY LAYERSbull A technology that operates only at the physical and datalink layers No protocol is
specified for the physical layer the choice is up to the user
bull Eliminates the extensive error checking necessary in X25 protocol
bull It uses simplified version of HDLC protocol in the datalink layerbull It uses routing and switching functions of the datalink layers Frames not packets
are switched
bull It uses PVCs (permanent virtual circuits) Identified through a DLCI (dalta linkconnection identifier)
bull A switch in frame relay performs error checking and routing Error correction is
left to the other protocols at the higher layers
bull Flow control is handled through setting the BECN (backwards explicit congestionnotification) and FECN (forward explicit congestion notification) in the address
field of the frame
bull
ASYNCHRONOUS TRANSFER MODE (ATM)
bull Is the cell relay protocol designed by the ATM forum and adopted by theITU-T
bull In ATM some software functions have moved to hardware this can
increase the data rate
Terms
Cell is the data packet is called a and is composed of 53 bytes (5 bytes of header and 48 bytes of payload) Because each cell is the same size and all are relatively small delay
and other problems associated with multiplexing different sized packets are avoided
A cell network is based on permanent virtual circuit (PVC) routing
bull Virtual Path Identifier (VPI) specifies the path a cell should take
1 Virtual path (VP) switching ndash channels within each VP remain with the VP
2 Virtual path and channel (VPC) switching ndash a channel from one VP may pass into
another VP
IXSDHSONET
Synchronous Optical Network (SONET)
Developed by ANSI
Synchronous Digital Hierarchy (SDH)
Developed by ITU-T
SONETSDH
The two are nearly identical ANSI and ITU-T defined standards that arefundamentally similar and ultimately compatible
Is a synchronous network a single clock is used to handle the timing of
transmissions and equipment across the entire network
SONET
It defines the hierarchy of signals called synchronous transport signals (STS)
Optical carrier (OC) levels are the implementation of STS
SONETSDH Rates
STS OC Rate (Mbps) STM
STS-1 OC-1 5184
STS-3 OC-3 15552 STM-1
STS-9 OC-9 46656 STM-3
STS-12 OC-12 62208 STM-4
STS-18 OC-18 93312 STM-6
STS-24 OC-24 124416 STM-8
STS-36 OC-36 186623 STM-12
STS-48 OC-48 248832 STM-16
STS-96 OC-96 497664 STM-32
STS-192 OC-192 995328 STM-64
STM-synchronous transport module
SONET Four Layers
1 Photonic layer is the lowest and performs physical layer activities
A frame at the photonic layer for STS-1 consists of 6480 bits (8000 framessec)
2-4 Section Line and Path layers correspond to the OSI modelrsquos datalink layer Eachof these layers is responsible for signal transfer across a specific portion of the
1 STS multiplexer combines several optical signals to make an STS signal2 Regenerator removes noise from optical signal
3 Adddrop multiplexer adds STS signals from different paths and removes STS signal
from a path
XTCPIP
Transmission Control ProtocolInternetworking Protocol (TCPIP)
Is a set of rules and procedures that governs the exchange of messages in an
internetwork Originally developed as a protocol for networks that wanted to be connected to
ARPANET a US Department of Defense project now known as Internet
Is a five-layer protocol suite whose bottom four layers match the OSI model fairly
closely The highest level the application layer corresponds to OSIrsquos top threelayers
Internet Protocol (IP) Is defined at the network layer
Unreliable and connectionless Is basically the set of rules for one network communicating with any other To be part of internet organization needs an internet network number unique
number to be included in any packet sent out of the network onto the internet
IP packet is known as datagram consists of a variable header and a variable data
field
IP Address
Uniquely defines the connection of a host to its network The host with more than
one IP address is multi-homed host
IP Addressing
32 bit binary number usually represented as 4 decimal values Equivalent to 4 octets ( 8 bits each decimal value ) Dotted decimal notation Consists of 2 parts the network and the node
Network ndash identifier of particular network on the internet
Host ndash identifier of a particular device which can be a server or a
Is the process where computers on a token-ring network detect a problem and
attempt to fix it
FDDI (Fiber Distributed Data Interface)
Uses fiber-optic cable and token-passing to create a very fast reliable networkoperating at speeds of 100 Mbps
It includes up to 500 nodes over a distance of 100 km It uses ring topology with two counter-rotating rings It is implement as true physical ring topology A break in a FDDI network results in packets being sent back on the second ring
1 End system (ES) is a network device that does not perform routing or other traffic
forwarding functions Typical ESs include such devices as terminals PCs and printers
2 Intermediate System (IS) is a network device that performs routing or other traffic-forwarding functions it includes devices such as routers switches and bridges
Intradomain IS communicates within a single autonomous system Interdomain IS communicates within and between autonomous systems
3 Area is a logical group of network segments and their attached devices Areas aresubdivisions of autonomous systems
4 Autonomous System (AS) is a collection of networks under a common administrationthat share a common routing strategy Autonomous system are subdivided into areas and
It involves three phases connection establishment- a single path between the
source and the destination systems is determined data transfer ndash transmitted sequentially
over the path that has been established and connection termination ndash termination of paththat has been establish
Connectionless
Offers two important advantages over connection-oriented service dynamic path
selection ndash enables traffic to be routed around network failures because paths are selectedon a packet-to-packet basis dynamic bandwidth allocation ndash used more efficiently
because network resources are not allocated a bandwidth that they will not use
Virtual Circuits
Switched Virtual CircuitA virtual circuit that is dynamically established on demand and terminated when
transmission is completed It has three phases circuit establishment data transfer and
circuit termination
Permanent Virtual Circuit
A permanently established virtual circuit consists of one mode the data transfer
Internetworking Devices
Hubs
bull A hub is a central network device that connects network devices in a startopology
bull Advanced hubs provide very high speed connectivity for FDDI Fast Ethernet
frame relay and ATM networks
bull It is also referred to as a concentrator (or switch) which is a device that can
have multiple inputs and outputs all active at a one time
bull Services offered by hubs
bull Provide a central unit from which to connect multiple nodes into one network
bull Permit large numbers of computers to be connected on single or multipleLANs
bull Reduce network congestion through centralizing network design
bull Provide multiprotocol services such as Ethernet-to-FDDI connectivity
bull Consolidate the network backbone
bull Enable high-speed communications
bull Provide connections for several different media types
bull Multiplexers are network devices that can receive multiple inputs and transmit
them to a shared network medium
bull A multiplexer is a switch that divides a communication medium into multiple
channels so several nodes can communicate at the same time
bull A signal that is multiplexed must be demultiplexed at the other endbull Multiplexers simply are switches used in old and new technology such as the
following
Telephone switching
Switching telecommunications lines to create multiple channels on a
single line Serial communications to enable more than one terminal to
communicate over a single line Fast Ethernet X25 ISDN frame relay ATM and other networking
technologies to create multiple communication channels over a single
communications cable
bull Work at the OSI physical level switching from channel to channel using one
of three physical methods
bull Time division multiplexing (TDM)
bull Frequency division multiplexing (FDM)
bull Wavelength division multiplexing (WDM)
Bridges
A bridge is a network device that connects different LAN segments using the same accessmethod
Bridges are used to
bull To extend a LAN when the maximum connections limit has been reached
bull To extend a LAN beyond the length limit
bull To segment LANs to reduce data traffic bottlenecks
bull To prevent unauthorized access to LAN (for security)
Standby indicator Pin 36 provides the confirmation signal from the DCE in response to
select standby (pin 32)
Send common Pin 37 provides a common signal return line for unbalanced circuits from
the DTE to the DCE
Electrical Specifications
bull EIA 449 uses two other standards to define its electrical specifications
RS-423 (for unbalanced circuits) and RS-422 (for balanced circuits)
RS-423 Unbalanced Mode
bull An unbalanced circuit specification meaning that it defines only one linefor propagating a signal All signals in this standard use a common return
(or ground) to complete the circuit
RS-422 Balanced Mode
bull A balanced circuit specification meaning that it defines two lines for the propagation of each signal Signals again use a common return (or ground)
for the return of the signal In balanced mode EIA-449 utilizes both pinsin each Category I but does not use the Category II pins The ratio of data
rate to distance is much higher that that of the unbalanced standard or of
EIA-232 10 Mbps for transmission of 40 feet bull In balanced mode two lines carry the same transmission it do not carry
identical signals The signal on one line is the complement of the signal
on the other When plotted the complement looks like a mirror image ofthe original signal Instead of listening to either actual signal the receiver
detects the differences between the two This mechanism makes a balanced circuit less susceptible to noise than an unbalanced circuit and
improves performance
EIA-530
bull A version of EIA-449 that uses DB-25 pins
bull The pin functions of EIA-530 are essentially the same of EIA-449
Category I plus three pins from Category II (the loopback circuits) Other pins in EIA-232 are omitted in EIA-530 such as ring indicator signal
quality detector and data signal rate selector
X21
bull Is an interface standard designed by ITU-T to address many problems
existing in the EIA interfaces and at the same time paves the way for alldigital communications
bull A large proportion of the circuits in the EIA interfaces are used forcontrol since these are necessary to implement control functions as
separate signals With a separate line control information is represented
only by positive and negative voltages But if control signals are encoded
using a meaningful control characters from a system such as ASCII it can be transmitted over data lines
bull X21 eliminates most of the control circuits of the EIA standards and
instead directs its traffic over the data circuits To make this consolidationof functionality possible both the DTE and the DCE must have added
circuit logic that enables them to transform the control codes into bit
streams that can be sent over the data line Both also need additional logicto discriminate between control information and data upon receipt
bull Design of X21 allows not only to use fewer pins but also to be used in
digital telecommunications where control information is sent from deviceto device over a network rather than just between a DTE and a DCE
bull X21 is useful both as an interface to connect digital computers to analogdevices such as modems and as a connector between digital computers and
digital interfaces such as ISDN and X25
Byte Timing
bull Another advantage offered by X21 is that of timing lines to control bytesynchronization in addition to the bit synchronization provided by the EIA
standards By adding a byte timing pulse improves the overall
synchronization of transmissions
Control and indication
bull Pins 3 and 5 of the DB-15 connector are used for the initial handshake or
agreement to begin transmitting Pin 3 is the equivalent of request to send
Pin 5 is the equivalent of clear to send
MODEMbull Modem stands for modulatordemodulator
bull A modulator converts a digital to an analog signalbull A demodulator converts an analog signal to a digital signal
bull The series of 1s and 0s are transformed through the mechanism of ASK
FSK PSK and QAM
Transmission Rate
Bandwidth
bull Every line has upper limit and a lower limit on the frequencies of the
signals it carry this limited range is called the bandwidth
It handles connection establishment and termination data transfer
and packet creation protocols Two types of PLP packets information and control
Up to 4096 channels may be multiplexed at the PLP level Specifies protocols to handle resizing of messages
FRAME RELAY LAYERSbull A technology that operates only at the physical and datalink layers No protocol is
specified for the physical layer the choice is up to the user
bull Eliminates the extensive error checking necessary in X25 protocol
bull It uses simplified version of HDLC protocol in the datalink layerbull It uses routing and switching functions of the datalink layers Frames not packets
are switched
bull It uses PVCs (permanent virtual circuits) Identified through a DLCI (dalta linkconnection identifier)
bull A switch in frame relay performs error checking and routing Error correction is
left to the other protocols at the higher layers
bull Flow control is handled through setting the BECN (backwards explicit congestionnotification) and FECN (forward explicit congestion notification) in the address
field of the frame
bull
ASYNCHRONOUS TRANSFER MODE (ATM)
bull Is the cell relay protocol designed by the ATM forum and adopted by theITU-T
bull In ATM some software functions have moved to hardware this can
increase the data rate
Terms
Cell is the data packet is called a and is composed of 53 bytes (5 bytes of header and 48 bytes of payload) Because each cell is the same size and all are relatively small delay
and other problems associated with multiplexing different sized packets are avoided
A cell network is based on permanent virtual circuit (PVC) routing
bull Virtual Path Identifier (VPI) specifies the path a cell should take
1 Virtual path (VP) switching ndash channels within each VP remain with the VP
2 Virtual path and channel (VPC) switching ndash a channel from one VP may pass into
another VP
IXSDHSONET
Synchronous Optical Network (SONET)
Developed by ANSI
Synchronous Digital Hierarchy (SDH)
Developed by ITU-T
SONETSDH
The two are nearly identical ANSI and ITU-T defined standards that arefundamentally similar and ultimately compatible
Is a synchronous network a single clock is used to handle the timing of
transmissions and equipment across the entire network
SONET
It defines the hierarchy of signals called synchronous transport signals (STS)
Optical carrier (OC) levels are the implementation of STS
SONETSDH Rates
STS OC Rate (Mbps) STM
STS-1 OC-1 5184
STS-3 OC-3 15552 STM-1
STS-9 OC-9 46656 STM-3
STS-12 OC-12 62208 STM-4
STS-18 OC-18 93312 STM-6
STS-24 OC-24 124416 STM-8
STS-36 OC-36 186623 STM-12
STS-48 OC-48 248832 STM-16
STS-96 OC-96 497664 STM-32
STS-192 OC-192 995328 STM-64
STM-synchronous transport module
SONET Four Layers
1 Photonic layer is the lowest and performs physical layer activities
A frame at the photonic layer for STS-1 consists of 6480 bits (8000 framessec)
2-4 Section Line and Path layers correspond to the OSI modelrsquos datalink layer Eachof these layers is responsible for signal transfer across a specific portion of the
1 STS multiplexer combines several optical signals to make an STS signal2 Regenerator removes noise from optical signal
3 Adddrop multiplexer adds STS signals from different paths and removes STS signal
from a path
XTCPIP
Transmission Control ProtocolInternetworking Protocol (TCPIP)
Is a set of rules and procedures that governs the exchange of messages in an
internetwork Originally developed as a protocol for networks that wanted to be connected to
ARPANET a US Department of Defense project now known as Internet
Is a five-layer protocol suite whose bottom four layers match the OSI model fairly
closely The highest level the application layer corresponds to OSIrsquos top threelayers
Internet Protocol (IP) Is defined at the network layer
Unreliable and connectionless Is basically the set of rules for one network communicating with any other To be part of internet organization needs an internet network number unique
number to be included in any packet sent out of the network onto the internet
IP packet is known as datagram consists of a variable header and a variable data
field
IP Address
Uniquely defines the connection of a host to its network The host with more than
one IP address is multi-homed host
IP Addressing
32 bit binary number usually represented as 4 decimal values Equivalent to 4 octets ( 8 bits each decimal value ) Dotted decimal notation Consists of 2 parts the network and the node
Network ndash identifier of particular network on the internet
Host ndash identifier of a particular device which can be a server or a
Is the process where computers on a token-ring network detect a problem and
attempt to fix it
FDDI (Fiber Distributed Data Interface)
Uses fiber-optic cable and token-passing to create a very fast reliable networkoperating at speeds of 100 Mbps
It includes up to 500 nodes over a distance of 100 km It uses ring topology with two counter-rotating rings It is implement as true physical ring topology A break in a FDDI network results in packets being sent back on the second ring
1 End system (ES) is a network device that does not perform routing or other traffic
forwarding functions Typical ESs include such devices as terminals PCs and printers
2 Intermediate System (IS) is a network device that performs routing or other traffic-forwarding functions it includes devices such as routers switches and bridges
Intradomain IS communicates within a single autonomous system Interdomain IS communicates within and between autonomous systems
3 Area is a logical group of network segments and their attached devices Areas aresubdivisions of autonomous systems
4 Autonomous System (AS) is a collection of networks under a common administrationthat share a common routing strategy Autonomous system are subdivided into areas and
It involves three phases connection establishment- a single path between the
source and the destination systems is determined data transfer ndash transmitted sequentially
over the path that has been established and connection termination ndash termination of paththat has been establish
Connectionless
Offers two important advantages over connection-oriented service dynamic path
selection ndash enables traffic to be routed around network failures because paths are selectedon a packet-to-packet basis dynamic bandwidth allocation ndash used more efficiently
because network resources are not allocated a bandwidth that they will not use
Virtual Circuits
Switched Virtual CircuitA virtual circuit that is dynamically established on demand and terminated when
transmission is completed It has three phases circuit establishment data transfer and
circuit termination
Permanent Virtual Circuit
A permanently established virtual circuit consists of one mode the data transfer
Internetworking Devices
Hubs
bull A hub is a central network device that connects network devices in a startopology
bull Advanced hubs provide very high speed connectivity for FDDI Fast Ethernet
frame relay and ATM networks
bull It is also referred to as a concentrator (or switch) which is a device that can
have multiple inputs and outputs all active at a one time
bull Services offered by hubs
bull Provide a central unit from which to connect multiple nodes into one network
bull Permit large numbers of computers to be connected on single or multipleLANs
bull Reduce network congestion through centralizing network design
bull Provide multiprotocol services such as Ethernet-to-FDDI connectivity
bull Consolidate the network backbone
bull Enable high-speed communications
bull Provide connections for several different media types
bull Multiplexers are network devices that can receive multiple inputs and transmit
them to a shared network medium
bull A multiplexer is a switch that divides a communication medium into multiple
channels so several nodes can communicate at the same time
bull A signal that is multiplexed must be demultiplexed at the other endbull Multiplexers simply are switches used in old and new technology such as the
following
Telephone switching
Switching telecommunications lines to create multiple channels on a
single line Serial communications to enable more than one terminal to
communicate over a single line Fast Ethernet X25 ISDN frame relay ATM and other networking
technologies to create multiple communication channels over a single
communications cable
bull Work at the OSI physical level switching from channel to channel using one
of three physical methods
bull Time division multiplexing (TDM)
bull Frequency division multiplexing (FDM)
bull Wavelength division multiplexing (WDM)
Bridges
A bridge is a network device that connects different LAN segments using the same accessmethod
Bridges are used to
bull To extend a LAN when the maximum connections limit has been reached
bull To extend a LAN beyond the length limit
bull To segment LANs to reduce data traffic bottlenecks
bull To prevent unauthorized access to LAN (for security)
Standby indicator Pin 36 provides the confirmation signal from the DCE in response to
select standby (pin 32)
Send common Pin 37 provides a common signal return line for unbalanced circuits from
the DTE to the DCE
Electrical Specifications
bull EIA 449 uses two other standards to define its electrical specifications
RS-423 (for unbalanced circuits) and RS-422 (for balanced circuits)
RS-423 Unbalanced Mode
bull An unbalanced circuit specification meaning that it defines only one linefor propagating a signal All signals in this standard use a common return
(or ground) to complete the circuit
RS-422 Balanced Mode
bull A balanced circuit specification meaning that it defines two lines for the propagation of each signal Signals again use a common return (or ground)
for the return of the signal In balanced mode EIA-449 utilizes both pinsin each Category I but does not use the Category II pins The ratio of data
rate to distance is much higher that that of the unbalanced standard or of
EIA-232 10 Mbps for transmission of 40 feet bull In balanced mode two lines carry the same transmission it do not carry
identical signals The signal on one line is the complement of the signal
on the other When plotted the complement looks like a mirror image ofthe original signal Instead of listening to either actual signal the receiver
detects the differences between the two This mechanism makes a balanced circuit less susceptible to noise than an unbalanced circuit and
improves performance
EIA-530
bull A version of EIA-449 that uses DB-25 pins
bull The pin functions of EIA-530 are essentially the same of EIA-449
Category I plus three pins from Category II (the loopback circuits) Other pins in EIA-232 are omitted in EIA-530 such as ring indicator signal
quality detector and data signal rate selector
X21
bull Is an interface standard designed by ITU-T to address many problems
existing in the EIA interfaces and at the same time paves the way for alldigital communications
bull A large proportion of the circuits in the EIA interfaces are used forcontrol since these are necessary to implement control functions as
separate signals With a separate line control information is represented
only by positive and negative voltages But if control signals are encoded
using a meaningful control characters from a system such as ASCII it can be transmitted over data lines
bull X21 eliminates most of the control circuits of the EIA standards and
instead directs its traffic over the data circuits To make this consolidationof functionality possible both the DTE and the DCE must have added
circuit logic that enables them to transform the control codes into bit
streams that can be sent over the data line Both also need additional logicto discriminate between control information and data upon receipt
bull Design of X21 allows not only to use fewer pins but also to be used in
digital telecommunications where control information is sent from deviceto device over a network rather than just between a DTE and a DCE
bull X21 is useful both as an interface to connect digital computers to analogdevices such as modems and as a connector between digital computers and
digital interfaces such as ISDN and X25
Byte Timing
bull Another advantage offered by X21 is that of timing lines to control bytesynchronization in addition to the bit synchronization provided by the EIA
standards By adding a byte timing pulse improves the overall
synchronization of transmissions
Control and indication
bull Pins 3 and 5 of the DB-15 connector are used for the initial handshake or
agreement to begin transmitting Pin 3 is the equivalent of request to send
Pin 5 is the equivalent of clear to send
MODEMbull Modem stands for modulatordemodulator
bull A modulator converts a digital to an analog signalbull A demodulator converts an analog signal to a digital signal
bull The series of 1s and 0s are transformed through the mechanism of ASK
FSK PSK and QAM
Transmission Rate
Bandwidth
bull Every line has upper limit and a lower limit on the frequencies of the
signals it carry this limited range is called the bandwidth
It handles connection establishment and termination data transfer
and packet creation protocols Two types of PLP packets information and control
Up to 4096 channels may be multiplexed at the PLP level Specifies protocols to handle resizing of messages
FRAME RELAY LAYERSbull A technology that operates only at the physical and datalink layers No protocol is
specified for the physical layer the choice is up to the user
bull Eliminates the extensive error checking necessary in X25 protocol
bull It uses simplified version of HDLC protocol in the datalink layerbull It uses routing and switching functions of the datalink layers Frames not packets
are switched
bull It uses PVCs (permanent virtual circuits) Identified through a DLCI (dalta linkconnection identifier)
bull A switch in frame relay performs error checking and routing Error correction is
left to the other protocols at the higher layers
bull Flow control is handled through setting the BECN (backwards explicit congestionnotification) and FECN (forward explicit congestion notification) in the address
field of the frame
bull
ASYNCHRONOUS TRANSFER MODE (ATM)
bull Is the cell relay protocol designed by the ATM forum and adopted by theITU-T
bull In ATM some software functions have moved to hardware this can
increase the data rate
Terms
Cell is the data packet is called a and is composed of 53 bytes (5 bytes of header and 48 bytes of payload) Because each cell is the same size and all are relatively small delay
and other problems associated with multiplexing different sized packets are avoided
A cell network is based on permanent virtual circuit (PVC) routing
bull Virtual Path Identifier (VPI) specifies the path a cell should take
1 Virtual path (VP) switching ndash channels within each VP remain with the VP
2 Virtual path and channel (VPC) switching ndash a channel from one VP may pass into
another VP
IXSDHSONET
Synchronous Optical Network (SONET)
Developed by ANSI
Synchronous Digital Hierarchy (SDH)
Developed by ITU-T
SONETSDH
The two are nearly identical ANSI and ITU-T defined standards that arefundamentally similar and ultimately compatible
Is a synchronous network a single clock is used to handle the timing of
transmissions and equipment across the entire network
SONET
It defines the hierarchy of signals called synchronous transport signals (STS)
Optical carrier (OC) levels are the implementation of STS
SONETSDH Rates
STS OC Rate (Mbps) STM
STS-1 OC-1 5184
STS-3 OC-3 15552 STM-1
STS-9 OC-9 46656 STM-3
STS-12 OC-12 62208 STM-4
STS-18 OC-18 93312 STM-6
STS-24 OC-24 124416 STM-8
STS-36 OC-36 186623 STM-12
STS-48 OC-48 248832 STM-16
STS-96 OC-96 497664 STM-32
STS-192 OC-192 995328 STM-64
STM-synchronous transport module
SONET Four Layers
1 Photonic layer is the lowest and performs physical layer activities
A frame at the photonic layer for STS-1 consists of 6480 bits (8000 framessec)
2-4 Section Line and Path layers correspond to the OSI modelrsquos datalink layer Eachof these layers is responsible for signal transfer across a specific portion of the
1 STS multiplexer combines several optical signals to make an STS signal2 Regenerator removes noise from optical signal
3 Adddrop multiplexer adds STS signals from different paths and removes STS signal
from a path
XTCPIP
Transmission Control ProtocolInternetworking Protocol (TCPIP)
Is a set of rules and procedures that governs the exchange of messages in an
internetwork Originally developed as a protocol for networks that wanted to be connected to
ARPANET a US Department of Defense project now known as Internet
Is a five-layer protocol suite whose bottom four layers match the OSI model fairly
closely The highest level the application layer corresponds to OSIrsquos top threelayers
Internet Protocol (IP) Is defined at the network layer
Unreliable and connectionless Is basically the set of rules for one network communicating with any other To be part of internet organization needs an internet network number unique
number to be included in any packet sent out of the network onto the internet
IP packet is known as datagram consists of a variable header and a variable data
field
IP Address
Uniquely defines the connection of a host to its network The host with more than
one IP address is multi-homed host
IP Addressing
32 bit binary number usually represented as 4 decimal values Equivalent to 4 octets ( 8 bits each decimal value ) Dotted decimal notation Consists of 2 parts the network and the node
Network ndash identifier of particular network on the internet
Host ndash identifier of a particular device which can be a server or a
1 End system (ES) is a network device that does not perform routing or other traffic
forwarding functions Typical ESs include such devices as terminals PCs and printers
2 Intermediate System (IS) is a network device that performs routing or other traffic-forwarding functions it includes devices such as routers switches and bridges
Intradomain IS communicates within a single autonomous system Interdomain IS communicates within and between autonomous systems
3 Area is a logical group of network segments and their attached devices Areas aresubdivisions of autonomous systems
4 Autonomous System (AS) is a collection of networks under a common administrationthat share a common routing strategy Autonomous system are subdivided into areas and
It involves three phases connection establishment- a single path between the
source and the destination systems is determined data transfer ndash transmitted sequentially
over the path that has been established and connection termination ndash termination of paththat has been establish
Connectionless
Offers two important advantages over connection-oriented service dynamic path
selection ndash enables traffic to be routed around network failures because paths are selectedon a packet-to-packet basis dynamic bandwidth allocation ndash used more efficiently
because network resources are not allocated a bandwidth that they will not use
Virtual Circuits
Switched Virtual CircuitA virtual circuit that is dynamically established on demand and terminated when
transmission is completed It has three phases circuit establishment data transfer and
circuit termination
Permanent Virtual Circuit
A permanently established virtual circuit consists of one mode the data transfer
Internetworking Devices
Hubs
bull A hub is a central network device that connects network devices in a startopology
bull Advanced hubs provide very high speed connectivity for FDDI Fast Ethernet
frame relay and ATM networks
bull It is also referred to as a concentrator (or switch) which is a device that can
have multiple inputs and outputs all active at a one time
bull Services offered by hubs
bull Provide a central unit from which to connect multiple nodes into one network
bull Permit large numbers of computers to be connected on single or multipleLANs
bull Reduce network congestion through centralizing network design
bull Provide multiprotocol services such as Ethernet-to-FDDI connectivity
bull Consolidate the network backbone
bull Enable high-speed communications
bull Provide connections for several different media types
bull Multiplexers are network devices that can receive multiple inputs and transmit
them to a shared network medium
bull A multiplexer is a switch that divides a communication medium into multiple
channels so several nodes can communicate at the same time
bull A signal that is multiplexed must be demultiplexed at the other endbull Multiplexers simply are switches used in old and new technology such as the
following
Telephone switching
Switching telecommunications lines to create multiple channels on a
single line Serial communications to enable more than one terminal to
communicate over a single line Fast Ethernet X25 ISDN frame relay ATM and other networking
technologies to create multiple communication channels over a single
communications cable
bull Work at the OSI physical level switching from channel to channel using one
of three physical methods
bull Time division multiplexing (TDM)
bull Frequency division multiplexing (FDM)
bull Wavelength division multiplexing (WDM)
Bridges
A bridge is a network device that connects different LAN segments using the same accessmethod
Bridges are used to
bull To extend a LAN when the maximum connections limit has been reached
bull To extend a LAN beyond the length limit
bull To segment LANs to reduce data traffic bottlenecks
bull To prevent unauthorized access to LAN (for security)
Standby indicator Pin 36 provides the confirmation signal from the DCE in response to
select standby (pin 32)
Send common Pin 37 provides a common signal return line for unbalanced circuits from
the DTE to the DCE
Electrical Specifications
bull EIA 449 uses two other standards to define its electrical specifications
RS-423 (for unbalanced circuits) and RS-422 (for balanced circuits)
RS-423 Unbalanced Mode
bull An unbalanced circuit specification meaning that it defines only one linefor propagating a signal All signals in this standard use a common return
(or ground) to complete the circuit
RS-422 Balanced Mode
bull A balanced circuit specification meaning that it defines two lines for the propagation of each signal Signals again use a common return (or ground)
for the return of the signal In balanced mode EIA-449 utilizes both pinsin each Category I but does not use the Category II pins The ratio of data
rate to distance is much higher that that of the unbalanced standard or of
EIA-232 10 Mbps for transmission of 40 feet bull In balanced mode two lines carry the same transmission it do not carry
identical signals The signal on one line is the complement of the signal
on the other When plotted the complement looks like a mirror image ofthe original signal Instead of listening to either actual signal the receiver
detects the differences between the two This mechanism makes a balanced circuit less susceptible to noise than an unbalanced circuit and
improves performance
EIA-530
bull A version of EIA-449 that uses DB-25 pins
bull The pin functions of EIA-530 are essentially the same of EIA-449
Category I plus three pins from Category II (the loopback circuits) Other pins in EIA-232 are omitted in EIA-530 such as ring indicator signal
quality detector and data signal rate selector
X21
bull Is an interface standard designed by ITU-T to address many problems
existing in the EIA interfaces and at the same time paves the way for alldigital communications
bull A large proportion of the circuits in the EIA interfaces are used forcontrol since these are necessary to implement control functions as
separate signals With a separate line control information is represented
only by positive and negative voltages But if control signals are encoded
using a meaningful control characters from a system such as ASCII it can be transmitted over data lines
bull X21 eliminates most of the control circuits of the EIA standards and
instead directs its traffic over the data circuits To make this consolidationof functionality possible both the DTE and the DCE must have added
circuit logic that enables them to transform the control codes into bit
streams that can be sent over the data line Both also need additional logicto discriminate between control information and data upon receipt
bull Design of X21 allows not only to use fewer pins but also to be used in
digital telecommunications where control information is sent from deviceto device over a network rather than just between a DTE and a DCE
bull X21 is useful both as an interface to connect digital computers to analogdevices such as modems and as a connector between digital computers and
digital interfaces such as ISDN and X25
Byte Timing
bull Another advantage offered by X21 is that of timing lines to control bytesynchronization in addition to the bit synchronization provided by the EIA
standards By adding a byte timing pulse improves the overall
synchronization of transmissions
Control and indication
bull Pins 3 and 5 of the DB-15 connector are used for the initial handshake or
agreement to begin transmitting Pin 3 is the equivalent of request to send
Pin 5 is the equivalent of clear to send
MODEMbull Modem stands for modulatordemodulator
bull A modulator converts a digital to an analog signalbull A demodulator converts an analog signal to a digital signal
bull The series of 1s and 0s are transformed through the mechanism of ASK
FSK PSK and QAM
Transmission Rate
Bandwidth
bull Every line has upper limit and a lower limit on the frequencies of the
signals it carry this limited range is called the bandwidth
It handles connection establishment and termination data transfer
and packet creation protocols Two types of PLP packets information and control
Up to 4096 channels may be multiplexed at the PLP level Specifies protocols to handle resizing of messages
FRAME RELAY LAYERSbull A technology that operates only at the physical and datalink layers No protocol is
specified for the physical layer the choice is up to the user
bull Eliminates the extensive error checking necessary in X25 protocol
bull It uses simplified version of HDLC protocol in the datalink layerbull It uses routing and switching functions of the datalink layers Frames not packets
are switched
bull It uses PVCs (permanent virtual circuits) Identified through a DLCI (dalta linkconnection identifier)
bull A switch in frame relay performs error checking and routing Error correction is
left to the other protocols at the higher layers
bull Flow control is handled through setting the BECN (backwards explicit congestionnotification) and FECN (forward explicit congestion notification) in the address
field of the frame
bull
ASYNCHRONOUS TRANSFER MODE (ATM)
bull Is the cell relay protocol designed by the ATM forum and adopted by theITU-T
bull In ATM some software functions have moved to hardware this can
increase the data rate
Terms
Cell is the data packet is called a and is composed of 53 bytes (5 bytes of header and 48 bytes of payload) Because each cell is the same size and all are relatively small delay
and other problems associated with multiplexing different sized packets are avoided
A cell network is based on permanent virtual circuit (PVC) routing
bull Virtual Path Identifier (VPI) specifies the path a cell should take
1 Virtual path (VP) switching ndash channels within each VP remain with the VP
2 Virtual path and channel (VPC) switching ndash a channel from one VP may pass into
another VP
IXSDHSONET
Synchronous Optical Network (SONET)
Developed by ANSI
Synchronous Digital Hierarchy (SDH)
Developed by ITU-T
SONETSDH
The two are nearly identical ANSI and ITU-T defined standards that arefundamentally similar and ultimately compatible
Is a synchronous network a single clock is used to handle the timing of
transmissions and equipment across the entire network
SONET
It defines the hierarchy of signals called synchronous transport signals (STS)
Optical carrier (OC) levels are the implementation of STS
SONETSDH Rates
STS OC Rate (Mbps) STM
STS-1 OC-1 5184
STS-3 OC-3 15552 STM-1
STS-9 OC-9 46656 STM-3
STS-12 OC-12 62208 STM-4
STS-18 OC-18 93312 STM-6
STS-24 OC-24 124416 STM-8
STS-36 OC-36 186623 STM-12
STS-48 OC-48 248832 STM-16
STS-96 OC-96 497664 STM-32
STS-192 OC-192 995328 STM-64
STM-synchronous transport module
SONET Four Layers
1 Photonic layer is the lowest and performs physical layer activities
A frame at the photonic layer for STS-1 consists of 6480 bits (8000 framessec)
2-4 Section Line and Path layers correspond to the OSI modelrsquos datalink layer Eachof these layers is responsible for signal transfer across a specific portion of the
1 STS multiplexer combines several optical signals to make an STS signal2 Regenerator removes noise from optical signal
3 Adddrop multiplexer adds STS signals from different paths and removes STS signal
from a path
XTCPIP
Transmission Control ProtocolInternetworking Protocol (TCPIP)
Is a set of rules and procedures that governs the exchange of messages in an
internetwork Originally developed as a protocol for networks that wanted to be connected to
ARPANET a US Department of Defense project now known as Internet
Is a five-layer protocol suite whose bottom four layers match the OSI model fairly
closely The highest level the application layer corresponds to OSIrsquos top threelayers
Internet Protocol (IP) Is defined at the network layer
Unreliable and connectionless Is basically the set of rules for one network communicating with any other To be part of internet organization needs an internet network number unique
number to be included in any packet sent out of the network onto the internet
IP packet is known as datagram consists of a variable header and a variable data
field
IP Address
Uniquely defines the connection of a host to its network The host with more than
one IP address is multi-homed host
IP Addressing
32 bit binary number usually represented as 4 decimal values Equivalent to 4 octets ( 8 bits each decimal value ) Dotted decimal notation Consists of 2 parts the network and the node
Network ndash identifier of particular network on the internet
Host ndash identifier of a particular device which can be a server or a
1 End system (ES) is a network device that does not perform routing or other traffic
forwarding functions Typical ESs include such devices as terminals PCs and printers
2 Intermediate System (IS) is a network device that performs routing or other traffic-forwarding functions it includes devices such as routers switches and bridges
Intradomain IS communicates within a single autonomous system Interdomain IS communicates within and between autonomous systems
3 Area is a logical group of network segments and their attached devices Areas aresubdivisions of autonomous systems
4 Autonomous System (AS) is a collection of networks under a common administrationthat share a common routing strategy Autonomous system are subdivided into areas and
It involves three phases connection establishment- a single path between the
source and the destination systems is determined data transfer ndash transmitted sequentially
over the path that has been established and connection termination ndash termination of paththat has been establish
Connectionless
Offers two important advantages over connection-oriented service dynamic path
selection ndash enables traffic to be routed around network failures because paths are selectedon a packet-to-packet basis dynamic bandwidth allocation ndash used more efficiently
because network resources are not allocated a bandwidth that they will not use
Virtual Circuits
Switched Virtual CircuitA virtual circuit that is dynamically established on demand and terminated when
transmission is completed It has three phases circuit establishment data transfer and
circuit termination
Permanent Virtual Circuit
A permanently established virtual circuit consists of one mode the data transfer
Internetworking Devices
Hubs
bull A hub is a central network device that connects network devices in a startopology
bull Advanced hubs provide very high speed connectivity for FDDI Fast Ethernet
frame relay and ATM networks
bull It is also referred to as a concentrator (or switch) which is a device that can
have multiple inputs and outputs all active at a one time
bull Services offered by hubs
bull Provide a central unit from which to connect multiple nodes into one network
bull Permit large numbers of computers to be connected on single or multipleLANs
bull Reduce network congestion through centralizing network design
bull Provide multiprotocol services such as Ethernet-to-FDDI connectivity
bull Consolidate the network backbone
bull Enable high-speed communications
bull Provide connections for several different media types
bull Multiplexers are network devices that can receive multiple inputs and transmit
them to a shared network medium
bull A multiplexer is a switch that divides a communication medium into multiple
channels so several nodes can communicate at the same time
bull A signal that is multiplexed must be demultiplexed at the other endbull Multiplexers simply are switches used in old and new technology such as the
following
Telephone switching
Switching telecommunications lines to create multiple channels on a
single line Serial communications to enable more than one terminal to
communicate over a single line Fast Ethernet X25 ISDN frame relay ATM and other networking
technologies to create multiple communication channels over a single
communications cable
bull Work at the OSI physical level switching from channel to channel using one
of three physical methods
bull Time division multiplexing (TDM)
bull Frequency division multiplexing (FDM)
bull Wavelength division multiplexing (WDM)
Bridges
A bridge is a network device that connects different LAN segments using the same accessmethod
Bridges are used to
bull To extend a LAN when the maximum connections limit has been reached
bull To extend a LAN beyond the length limit
bull To segment LANs to reduce data traffic bottlenecks
bull To prevent unauthorized access to LAN (for security)
Standby indicator Pin 36 provides the confirmation signal from the DCE in response to
select standby (pin 32)
Send common Pin 37 provides a common signal return line for unbalanced circuits from
the DTE to the DCE
Electrical Specifications
bull EIA 449 uses two other standards to define its electrical specifications
RS-423 (for unbalanced circuits) and RS-422 (for balanced circuits)
RS-423 Unbalanced Mode
bull An unbalanced circuit specification meaning that it defines only one linefor propagating a signal All signals in this standard use a common return
(or ground) to complete the circuit
RS-422 Balanced Mode
bull A balanced circuit specification meaning that it defines two lines for the propagation of each signal Signals again use a common return (or ground)
for the return of the signal In balanced mode EIA-449 utilizes both pinsin each Category I but does not use the Category II pins The ratio of data
rate to distance is much higher that that of the unbalanced standard or of
EIA-232 10 Mbps for transmission of 40 feet bull In balanced mode two lines carry the same transmission it do not carry
identical signals The signal on one line is the complement of the signal
on the other When plotted the complement looks like a mirror image ofthe original signal Instead of listening to either actual signal the receiver
detects the differences between the two This mechanism makes a balanced circuit less susceptible to noise than an unbalanced circuit and
improves performance
EIA-530
bull A version of EIA-449 that uses DB-25 pins
bull The pin functions of EIA-530 are essentially the same of EIA-449
Category I plus three pins from Category II (the loopback circuits) Other pins in EIA-232 are omitted in EIA-530 such as ring indicator signal
quality detector and data signal rate selector
X21
bull Is an interface standard designed by ITU-T to address many problems
existing in the EIA interfaces and at the same time paves the way for alldigital communications
bull A large proportion of the circuits in the EIA interfaces are used forcontrol since these are necessary to implement control functions as
separate signals With a separate line control information is represented
only by positive and negative voltages But if control signals are encoded
using a meaningful control characters from a system such as ASCII it can be transmitted over data lines
bull X21 eliminates most of the control circuits of the EIA standards and
instead directs its traffic over the data circuits To make this consolidationof functionality possible both the DTE and the DCE must have added
circuit logic that enables them to transform the control codes into bit
streams that can be sent over the data line Both also need additional logicto discriminate between control information and data upon receipt
bull Design of X21 allows not only to use fewer pins but also to be used in
digital telecommunications where control information is sent from deviceto device over a network rather than just between a DTE and a DCE
bull X21 is useful both as an interface to connect digital computers to analogdevices such as modems and as a connector between digital computers and
digital interfaces such as ISDN and X25
Byte Timing
bull Another advantage offered by X21 is that of timing lines to control bytesynchronization in addition to the bit synchronization provided by the EIA
standards By adding a byte timing pulse improves the overall
synchronization of transmissions
Control and indication
bull Pins 3 and 5 of the DB-15 connector are used for the initial handshake or
agreement to begin transmitting Pin 3 is the equivalent of request to send
Pin 5 is the equivalent of clear to send
MODEMbull Modem stands for modulatordemodulator
bull A modulator converts a digital to an analog signalbull A demodulator converts an analog signal to a digital signal
bull The series of 1s and 0s are transformed through the mechanism of ASK
FSK PSK and QAM
Transmission Rate
Bandwidth
bull Every line has upper limit and a lower limit on the frequencies of the
signals it carry this limited range is called the bandwidth
It handles connection establishment and termination data transfer
and packet creation protocols Two types of PLP packets information and control
Up to 4096 channels may be multiplexed at the PLP level Specifies protocols to handle resizing of messages
FRAME RELAY LAYERSbull A technology that operates only at the physical and datalink layers No protocol is
specified for the physical layer the choice is up to the user
bull Eliminates the extensive error checking necessary in X25 protocol
bull It uses simplified version of HDLC protocol in the datalink layerbull It uses routing and switching functions of the datalink layers Frames not packets
are switched
bull It uses PVCs (permanent virtual circuits) Identified through a DLCI (dalta linkconnection identifier)
bull A switch in frame relay performs error checking and routing Error correction is
left to the other protocols at the higher layers
bull Flow control is handled through setting the BECN (backwards explicit congestionnotification) and FECN (forward explicit congestion notification) in the address
field of the frame
bull
ASYNCHRONOUS TRANSFER MODE (ATM)
bull Is the cell relay protocol designed by the ATM forum and adopted by theITU-T
bull In ATM some software functions have moved to hardware this can
increase the data rate
Terms
Cell is the data packet is called a and is composed of 53 bytes (5 bytes of header and 48 bytes of payload) Because each cell is the same size and all are relatively small delay
and other problems associated with multiplexing different sized packets are avoided
A cell network is based on permanent virtual circuit (PVC) routing
bull Virtual Path Identifier (VPI) specifies the path a cell should take
1 Virtual path (VP) switching ndash channels within each VP remain with the VP
2 Virtual path and channel (VPC) switching ndash a channel from one VP may pass into
another VP
IXSDHSONET
Synchronous Optical Network (SONET)
Developed by ANSI
Synchronous Digital Hierarchy (SDH)
Developed by ITU-T
SONETSDH
The two are nearly identical ANSI and ITU-T defined standards that arefundamentally similar and ultimately compatible
Is a synchronous network a single clock is used to handle the timing of
transmissions and equipment across the entire network
SONET
It defines the hierarchy of signals called synchronous transport signals (STS)
Optical carrier (OC) levels are the implementation of STS
SONETSDH Rates
STS OC Rate (Mbps) STM
STS-1 OC-1 5184
STS-3 OC-3 15552 STM-1
STS-9 OC-9 46656 STM-3
STS-12 OC-12 62208 STM-4
STS-18 OC-18 93312 STM-6
STS-24 OC-24 124416 STM-8
STS-36 OC-36 186623 STM-12
STS-48 OC-48 248832 STM-16
STS-96 OC-96 497664 STM-32
STS-192 OC-192 995328 STM-64
STM-synchronous transport module
SONET Four Layers
1 Photonic layer is the lowest and performs physical layer activities
A frame at the photonic layer for STS-1 consists of 6480 bits (8000 framessec)
2-4 Section Line and Path layers correspond to the OSI modelrsquos datalink layer Eachof these layers is responsible for signal transfer across a specific portion of the
1 STS multiplexer combines several optical signals to make an STS signal2 Regenerator removes noise from optical signal
3 Adddrop multiplexer adds STS signals from different paths and removes STS signal
from a path
XTCPIP
Transmission Control ProtocolInternetworking Protocol (TCPIP)
Is a set of rules and procedures that governs the exchange of messages in an
internetwork Originally developed as a protocol for networks that wanted to be connected to
ARPANET a US Department of Defense project now known as Internet
Is a five-layer protocol suite whose bottom four layers match the OSI model fairly
closely The highest level the application layer corresponds to OSIrsquos top threelayers
Internet Protocol (IP) Is defined at the network layer
Unreliable and connectionless Is basically the set of rules for one network communicating with any other To be part of internet organization needs an internet network number unique
number to be included in any packet sent out of the network onto the internet
IP packet is known as datagram consists of a variable header and a variable data
field
IP Address
Uniquely defines the connection of a host to its network The host with more than
one IP address is multi-homed host
IP Addressing
32 bit binary number usually represented as 4 decimal values Equivalent to 4 octets ( 8 bits each decimal value ) Dotted decimal notation Consists of 2 parts the network and the node
Network ndash identifier of particular network on the internet
Host ndash identifier of a particular device which can be a server or a
It involves three phases connection establishment- a single path between the
source and the destination systems is determined data transfer ndash transmitted sequentially
over the path that has been established and connection termination ndash termination of paththat has been establish
Connectionless
Offers two important advantages over connection-oriented service dynamic path
selection ndash enables traffic to be routed around network failures because paths are selectedon a packet-to-packet basis dynamic bandwidth allocation ndash used more efficiently
because network resources are not allocated a bandwidth that they will not use
Virtual Circuits
Switched Virtual CircuitA virtual circuit that is dynamically established on demand and terminated when
transmission is completed It has three phases circuit establishment data transfer and
circuit termination
Permanent Virtual Circuit
A permanently established virtual circuit consists of one mode the data transfer
Internetworking Devices
Hubs
bull A hub is a central network device that connects network devices in a startopology
bull Advanced hubs provide very high speed connectivity for FDDI Fast Ethernet
frame relay and ATM networks
bull It is also referred to as a concentrator (or switch) which is a device that can
have multiple inputs and outputs all active at a one time
bull Services offered by hubs
bull Provide a central unit from which to connect multiple nodes into one network
bull Permit large numbers of computers to be connected on single or multipleLANs
bull Reduce network congestion through centralizing network design
bull Provide multiprotocol services such as Ethernet-to-FDDI connectivity
bull Consolidate the network backbone
bull Enable high-speed communications
bull Provide connections for several different media types
bull Multiplexers are network devices that can receive multiple inputs and transmit
them to a shared network medium
bull A multiplexer is a switch that divides a communication medium into multiple
channels so several nodes can communicate at the same time
bull A signal that is multiplexed must be demultiplexed at the other endbull Multiplexers simply are switches used in old and new technology such as the
following
Telephone switching
Switching telecommunications lines to create multiple channels on a
single line Serial communications to enable more than one terminal to
communicate over a single line Fast Ethernet X25 ISDN frame relay ATM and other networking
technologies to create multiple communication channels over a single
communications cable
bull Work at the OSI physical level switching from channel to channel using one
of three physical methods
bull Time division multiplexing (TDM)
bull Frequency division multiplexing (FDM)
bull Wavelength division multiplexing (WDM)
Bridges
A bridge is a network device that connects different LAN segments using the same accessmethod
Bridges are used to
bull To extend a LAN when the maximum connections limit has been reached
bull To extend a LAN beyond the length limit
bull To segment LANs to reduce data traffic bottlenecks
bull To prevent unauthorized access to LAN (for security)
Standby indicator Pin 36 provides the confirmation signal from the DCE in response to
select standby (pin 32)
Send common Pin 37 provides a common signal return line for unbalanced circuits from
the DTE to the DCE
Electrical Specifications
bull EIA 449 uses two other standards to define its electrical specifications
RS-423 (for unbalanced circuits) and RS-422 (for balanced circuits)
RS-423 Unbalanced Mode
bull An unbalanced circuit specification meaning that it defines only one linefor propagating a signal All signals in this standard use a common return
(or ground) to complete the circuit
RS-422 Balanced Mode
bull A balanced circuit specification meaning that it defines two lines for the propagation of each signal Signals again use a common return (or ground)
for the return of the signal In balanced mode EIA-449 utilizes both pinsin each Category I but does not use the Category II pins The ratio of data
rate to distance is much higher that that of the unbalanced standard or of
EIA-232 10 Mbps for transmission of 40 feet bull In balanced mode two lines carry the same transmission it do not carry
identical signals The signal on one line is the complement of the signal
on the other When plotted the complement looks like a mirror image ofthe original signal Instead of listening to either actual signal the receiver
detects the differences between the two This mechanism makes a balanced circuit less susceptible to noise than an unbalanced circuit and
improves performance
EIA-530
bull A version of EIA-449 that uses DB-25 pins
bull The pin functions of EIA-530 are essentially the same of EIA-449
Category I plus three pins from Category II (the loopback circuits) Other pins in EIA-232 are omitted in EIA-530 such as ring indicator signal
quality detector and data signal rate selector
X21
bull Is an interface standard designed by ITU-T to address many problems
existing in the EIA interfaces and at the same time paves the way for alldigital communications
bull A large proportion of the circuits in the EIA interfaces are used forcontrol since these are necessary to implement control functions as
separate signals With a separate line control information is represented
only by positive and negative voltages But if control signals are encoded
using a meaningful control characters from a system such as ASCII it can be transmitted over data lines
bull X21 eliminates most of the control circuits of the EIA standards and
instead directs its traffic over the data circuits To make this consolidationof functionality possible both the DTE and the DCE must have added
circuit logic that enables them to transform the control codes into bit
streams that can be sent over the data line Both also need additional logicto discriminate between control information and data upon receipt
bull Design of X21 allows not only to use fewer pins but also to be used in
digital telecommunications where control information is sent from deviceto device over a network rather than just between a DTE and a DCE
bull X21 is useful both as an interface to connect digital computers to analogdevices such as modems and as a connector between digital computers and
digital interfaces such as ISDN and X25
Byte Timing
bull Another advantage offered by X21 is that of timing lines to control bytesynchronization in addition to the bit synchronization provided by the EIA
standards By adding a byte timing pulse improves the overall
synchronization of transmissions
Control and indication
bull Pins 3 and 5 of the DB-15 connector are used for the initial handshake or
agreement to begin transmitting Pin 3 is the equivalent of request to send
Pin 5 is the equivalent of clear to send
MODEMbull Modem stands for modulatordemodulator
bull A modulator converts a digital to an analog signalbull A demodulator converts an analog signal to a digital signal
bull The series of 1s and 0s are transformed through the mechanism of ASK
FSK PSK and QAM
Transmission Rate
Bandwidth
bull Every line has upper limit and a lower limit on the frequencies of the
signals it carry this limited range is called the bandwidth
It handles connection establishment and termination data transfer
and packet creation protocols Two types of PLP packets information and control
Up to 4096 channels may be multiplexed at the PLP level Specifies protocols to handle resizing of messages
FRAME RELAY LAYERSbull A technology that operates only at the physical and datalink layers No protocol is
specified for the physical layer the choice is up to the user
bull Eliminates the extensive error checking necessary in X25 protocol
bull It uses simplified version of HDLC protocol in the datalink layerbull It uses routing and switching functions of the datalink layers Frames not packets
are switched
bull It uses PVCs (permanent virtual circuits) Identified through a DLCI (dalta linkconnection identifier)
bull A switch in frame relay performs error checking and routing Error correction is
left to the other protocols at the higher layers
bull Flow control is handled through setting the BECN (backwards explicit congestionnotification) and FECN (forward explicit congestion notification) in the address
field of the frame
bull
ASYNCHRONOUS TRANSFER MODE (ATM)
bull Is the cell relay protocol designed by the ATM forum and adopted by theITU-T
bull In ATM some software functions have moved to hardware this can
increase the data rate
Terms
Cell is the data packet is called a and is composed of 53 bytes (5 bytes of header and 48 bytes of payload) Because each cell is the same size and all are relatively small delay
and other problems associated with multiplexing different sized packets are avoided
A cell network is based on permanent virtual circuit (PVC) routing
bull Virtual Path Identifier (VPI) specifies the path a cell should take
1 Virtual path (VP) switching ndash channels within each VP remain with the VP
2 Virtual path and channel (VPC) switching ndash a channel from one VP may pass into
another VP
IXSDHSONET
Synchronous Optical Network (SONET)
Developed by ANSI
Synchronous Digital Hierarchy (SDH)
Developed by ITU-T
SONETSDH
The two are nearly identical ANSI and ITU-T defined standards that arefundamentally similar and ultimately compatible
Is a synchronous network a single clock is used to handle the timing of
transmissions and equipment across the entire network
SONET
It defines the hierarchy of signals called synchronous transport signals (STS)
Optical carrier (OC) levels are the implementation of STS
SONETSDH Rates
STS OC Rate (Mbps) STM
STS-1 OC-1 5184
STS-3 OC-3 15552 STM-1
STS-9 OC-9 46656 STM-3
STS-12 OC-12 62208 STM-4
STS-18 OC-18 93312 STM-6
STS-24 OC-24 124416 STM-8
STS-36 OC-36 186623 STM-12
STS-48 OC-48 248832 STM-16
STS-96 OC-96 497664 STM-32
STS-192 OC-192 995328 STM-64
STM-synchronous transport module
SONET Four Layers
1 Photonic layer is the lowest and performs physical layer activities
A frame at the photonic layer for STS-1 consists of 6480 bits (8000 framessec)
2-4 Section Line and Path layers correspond to the OSI modelrsquos datalink layer Eachof these layers is responsible for signal transfer across a specific portion of the
1 STS multiplexer combines several optical signals to make an STS signal2 Regenerator removes noise from optical signal
3 Adddrop multiplexer adds STS signals from different paths and removes STS signal
from a path
XTCPIP
Transmission Control ProtocolInternetworking Protocol (TCPIP)
Is a set of rules and procedures that governs the exchange of messages in an
internetwork Originally developed as a protocol for networks that wanted to be connected to
ARPANET a US Department of Defense project now known as Internet
Is a five-layer protocol suite whose bottom four layers match the OSI model fairly
closely The highest level the application layer corresponds to OSIrsquos top threelayers
Internet Protocol (IP) Is defined at the network layer
Unreliable and connectionless Is basically the set of rules for one network communicating with any other To be part of internet organization needs an internet network number unique
number to be included in any packet sent out of the network onto the internet
IP packet is known as datagram consists of a variable header and a variable data
field
IP Address
Uniquely defines the connection of a host to its network The host with more than
one IP address is multi-homed host
IP Addressing
32 bit binary number usually represented as 4 decimal values Equivalent to 4 octets ( 8 bits each decimal value ) Dotted decimal notation Consists of 2 parts the network and the node
Network ndash identifier of particular network on the internet
Host ndash identifier of a particular device which can be a server or a
bull Multiplexers are network devices that can receive multiple inputs and transmit
them to a shared network medium
bull A multiplexer is a switch that divides a communication medium into multiple
channels so several nodes can communicate at the same time
bull A signal that is multiplexed must be demultiplexed at the other endbull Multiplexers simply are switches used in old and new technology such as the
following
Telephone switching
Switching telecommunications lines to create multiple channels on a
single line Serial communications to enable more than one terminal to
communicate over a single line Fast Ethernet X25 ISDN frame relay ATM and other networking
technologies to create multiple communication channels over a single
communications cable
bull Work at the OSI physical level switching from channel to channel using one
of three physical methods
bull Time division multiplexing (TDM)
bull Frequency division multiplexing (FDM)
bull Wavelength division multiplexing (WDM)
Bridges
A bridge is a network device that connects different LAN segments using the same accessmethod
Bridges are used to
bull To extend a LAN when the maximum connections limit has been reached
bull To extend a LAN beyond the length limit
bull To segment LANs to reduce data traffic bottlenecks
bull To prevent unauthorized access to LAN (for security)
Standby indicator Pin 36 provides the confirmation signal from the DCE in response to
select standby (pin 32)
Send common Pin 37 provides a common signal return line for unbalanced circuits from
the DTE to the DCE
Electrical Specifications
bull EIA 449 uses two other standards to define its electrical specifications
RS-423 (for unbalanced circuits) and RS-422 (for balanced circuits)
RS-423 Unbalanced Mode
bull An unbalanced circuit specification meaning that it defines only one linefor propagating a signal All signals in this standard use a common return
(or ground) to complete the circuit
RS-422 Balanced Mode
bull A balanced circuit specification meaning that it defines two lines for the propagation of each signal Signals again use a common return (or ground)
for the return of the signal In balanced mode EIA-449 utilizes both pinsin each Category I but does not use the Category II pins The ratio of data
rate to distance is much higher that that of the unbalanced standard or of
EIA-232 10 Mbps for transmission of 40 feet bull In balanced mode two lines carry the same transmission it do not carry
identical signals The signal on one line is the complement of the signal
on the other When plotted the complement looks like a mirror image ofthe original signal Instead of listening to either actual signal the receiver
detects the differences between the two This mechanism makes a balanced circuit less susceptible to noise than an unbalanced circuit and
improves performance
EIA-530
bull A version of EIA-449 that uses DB-25 pins
bull The pin functions of EIA-530 are essentially the same of EIA-449
Category I plus three pins from Category II (the loopback circuits) Other pins in EIA-232 are omitted in EIA-530 such as ring indicator signal
quality detector and data signal rate selector
X21
bull Is an interface standard designed by ITU-T to address many problems
existing in the EIA interfaces and at the same time paves the way for alldigital communications
bull A large proportion of the circuits in the EIA interfaces are used forcontrol since these are necessary to implement control functions as
separate signals With a separate line control information is represented
only by positive and negative voltages But if control signals are encoded
using a meaningful control characters from a system such as ASCII it can be transmitted over data lines
bull X21 eliminates most of the control circuits of the EIA standards and
instead directs its traffic over the data circuits To make this consolidationof functionality possible both the DTE and the DCE must have added
circuit logic that enables them to transform the control codes into bit
streams that can be sent over the data line Both also need additional logicto discriminate between control information and data upon receipt
bull Design of X21 allows not only to use fewer pins but also to be used in
digital telecommunications where control information is sent from deviceto device over a network rather than just between a DTE and a DCE
bull X21 is useful both as an interface to connect digital computers to analogdevices such as modems and as a connector between digital computers and
digital interfaces such as ISDN and X25
Byte Timing
bull Another advantage offered by X21 is that of timing lines to control bytesynchronization in addition to the bit synchronization provided by the EIA
standards By adding a byte timing pulse improves the overall
synchronization of transmissions
Control and indication
bull Pins 3 and 5 of the DB-15 connector are used for the initial handshake or
agreement to begin transmitting Pin 3 is the equivalent of request to send
Pin 5 is the equivalent of clear to send
MODEMbull Modem stands for modulatordemodulator
bull A modulator converts a digital to an analog signalbull A demodulator converts an analog signal to a digital signal
bull The series of 1s and 0s are transformed through the mechanism of ASK
FSK PSK and QAM
Transmission Rate
Bandwidth
bull Every line has upper limit and a lower limit on the frequencies of the
signals it carry this limited range is called the bandwidth
It handles connection establishment and termination data transfer
and packet creation protocols Two types of PLP packets information and control
Up to 4096 channels may be multiplexed at the PLP level Specifies protocols to handle resizing of messages
FRAME RELAY LAYERSbull A technology that operates only at the physical and datalink layers No protocol is
specified for the physical layer the choice is up to the user
bull Eliminates the extensive error checking necessary in X25 protocol
bull It uses simplified version of HDLC protocol in the datalink layerbull It uses routing and switching functions of the datalink layers Frames not packets
are switched
bull It uses PVCs (permanent virtual circuits) Identified through a DLCI (dalta linkconnection identifier)
bull A switch in frame relay performs error checking and routing Error correction is
left to the other protocols at the higher layers
bull Flow control is handled through setting the BECN (backwards explicit congestionnotification) and FECN (forward explicit congestion notification) in the address
field of the frame
bull
ASYNCHRONOUS TRANSFER MODE (ATM)
bull Is the cell relay protocol designed by the ATM forum and adopted by theITU-T
bull In ATM some software functions have moved to hardware this can
increase the data rate
Terms
Cell is the data packet is called a and is composed of 53 bytes (5 bytes of header and 48 bytes of payload) Because each cell is the same size and all are relatively small delay
and other problems associated with multiplexing different sized packets are avoided
A cell network is based on permanent virtual circuit (PVC) routing
bull Virtual Path Identifier (VPI) specifies the path a cell should take
1 Virtual path (VP) switching ndash channels within each VP remain with the VP
2 Virtual path and channel (VPC) switching ndash a channel from one VP may pass into
another VP
IXSDHSONET
Synchronous Optical Network (SONET)
Developed by ANSI
Synchronous Digital Hierarchy (SDH)
Developed by ITU-T
SONETSDH
The two are nearly identical ANSI and ITU-T defined standards that arefundamentally similar and ultimately compatible
Is a synchronous network a single clock is used to handle the timing of
transmissions and equipment across the entire network
SONET
It defines the hierarchy of signals called synchronous transport signals (STS)
Optical carrier (OC) levels are the implementation of STS
SONETSDH Rates
STS OC Rate (Mbps) STM
STS-1 OC-1 5184
STS-3 OC-3 15552 STM-1
STS-9 OC-9 46656 STM-3
STS-12 OC-12 62208 STM-4
STS-18 OC-18 93312 STM-6
STS-24 OC-24 124416 STM-8
STS-36 OC-36 186623 STM-12
STS-48 OC-48 248832 STM-16
STS-96 OC-96 497664 STM-32
STS-192 OC-192 995328 STM-64
STM-synchronous transport module
SONET Four Layers
1 Photonic layer is the lowest and performs physical layer activities
A frame at the photonic layer for STS-1 consists of 6480 bits (8000 framessec)
2-4 Section Line and Path layers correspond to the OSI modelrsquos datalink layer Eachof these layers is responsible for signal transfer across a specific portion of the
1 STS multiplexer combines several optical signals to make an STS signal2 Regenerator removes noise from optical signal
3 Adddrop multiplexer adds STS signals from different paths and removes STS signal
from a path
XTCPIP
Transmission Control ProtocolInternetworking Protocol (TCPIP)
Is a set of rules and procedures that governs the exchange of messages in an
internetwork Originally developed as a protocol for networks that wanted to be connected to
ARPANET a US Department of Defense project now known as Internet
Is a five-layer protocol suite whose bottom four layers match the OSI model fairly
closely The highest level the application layer corresponds to OSIrsquos top threelayers
Internet Protocol (IP) Is defined at the network layer
Unreliable and connectionless Is basically the set of rules for one network communicating with any other To be part of internet organization needs an internet network number unique
number to be included in any packet sent out of the network onto the internet
IP packet is known as datagram consists of a variable header and a variable data
field
IP Address
Uniquely defines the connection of a host to its network The host with more than
one IP address is multi-homed host
IP Addressing
32 bit binary number usually represented as 4 decimal values Equivalent to 4 octets ( 8 bits each decimal value ) Dotted decimal notation Consists of 2 parts the network and the node
Network ndash identifier of particular network on the internet
Host ndash identifier of a particular device which can be a server or a
Standby indicator Pin 36 provides the confirmation signal from the DCE in response to
select standby (pin 32)
Send common Pin 37 provides a common signal return line for unbalanced circuits from
the DTE to the DCE
Electrical Specifications
bull EIA 449 uses two other standards to define its electrical specifications
RS-423 (for unbalanced circuits) and RS-422 (for balanced circuits)
RS-423 Unbalanced Mode
bull An unbalanced circuit specification meaning that it defines only one linefor propagating a signal All signals in this standard use a common return
(or ground) to complete the circuit
RS-422 Balanced Mode
bull A balanced circuit specification meaning that it defines two lines for the propagation of each signal Signals again use a common return (or ground)
for the return of the signal In balanced mode EIA-449 utilizes both pinsin each Category I but does not use the Category II pins The ratio of data
rate to distance is much higher that that of the unbalanced standard or of
EIA-232 10 Mbps for transmission of 40 feet bull In balanced mode two lines carry the same transmission it do not carry
identical signals The signal on one line is the complement of the signal
on the other When plotted the complement looks like a mirror image ofthe original signal Instead of listening to either actual signal the receiver
detects the differences between the two This mechanism makes a balanced circuit less susceptible to noise than an unbalanced circuit and
improves performance
EIA-530
bull A version of EIA-449 that uses DB-25 pins
bull The pin functions of EIA-530 are essentially the same of EIA-449
Category I plus three pins from Category II (the loopback circuits) Other pins in EIA-232 are omitted in EIA-530 such as ring indicator signal
quality detector and data signal rate selector
X21
bull Is an interface standard designed by ITU-T to address many problems
existing in the EIA interfaces and at the same time paves the way for alldigital communications
bull A large proportion of the circuits in the EIA interfaces are used forcontrol since these are necessary to implement control functions as
separate signals With a separate line control information is represented
only by positive and negative voltages But if control signals are encoded
using a meaningful control characters from a system such as ASCII it can be transmitted over data lines
bull X21 eliminates most of the control circuits of the EIA standards and
instead directs its traffic over the data circuits To make this consolidationof functionality possible both the DTE and the DCE must have added
circuit logic that enables them to transform the control codes into bit
streams that can be sent over the data line Both also need additional logicto discriminate between control information and data upon receipt
bull Design of X21 allows not only to use fewer pins but also to be used in
digital telecommunications where control information is sent from deviceto device over a network rather than just between a DTE and a DCE
bull X21 is useful both as an interface to connect digital computers to analogdevices such as modems and as a connector between digital computers and
digital interfaces such as ISDN and X25
Byte Timing
bull Another advantage offered by X21 is that of timing lines to control bytesynchronization in addition to the bit synchronization provided by the EIA
standards By adding a byte timing pulse improves the overall
synchronization of transmissions
Control and indication
bull Pins 3 and 5 of the DB-15 connector are used for the initial handshake or
agreement to begin transmitting Pin 3 is the equivalent of request to send
Pin 5 is the equivalent of clear to send
MODEMbull Modem stands for modulatordemodulator
bull A modulator converts a digital to an analog signalbull A demodulator converts an analog signal to a digital signal
bull The series of 1s and 0s are transformed through the mechanism of ASK
FSK PSK and QAM
Transmission Rate
Bandwidth
bull Every line has upper limit and a lower limit on the frequencies of the
signals it carry this limited range is called the bandwidth
It handles connection establishment and termination data transfer
and packet creation protocols Two types of PLP packets information and control
Up to 4096 channels may be multiplexed at the PLP level Specifies protocols to handle resizing of messages
FRAME RELAY LAYERSbull A technology that operates only at the physical and datalink layers No protocol is
specified for the physical layer the choice is up to the user
bull Eliminates the extensive error checking necessary in X25 protocol
bull It uses simplified version of HDLC protocol in the datalink layerbull It uses routing and switching functions of the datalink layers Frames not packets
are switched
bull It uses PVCs (permanent virtual circuits) Identified through a DLCI (dalta linkconnection identifier)
bull A switch in frame relay performs error checking and routing Error correction is
left to the other protocols at the higher layers
bull Flow control is handled through setting the BECN (backwards explicit congestionnotification) and FECN (forward explicit congestion notification) in the address
field of the frame
bull
ASYNCHRONOUS TRANSFER MODE (ATM)
bull Is the cell relay protocol designed by the ATM forum and adopted by theITU-T
bull In ATM some software functions have moved to hardware this can
increase the data rate
Terms
Cell is the data packet is called a and is composed of 53 bytes (5 bytes of header and 48 bytes of payload) Because each cell is the same size and all are relatively small delay
and other problems associated with multiplexing different sized packets are avoided
A cell network is based on permanent virtual circuit (PVC) routing
bull Virtual Path Identifier (VPI) specifies the path a cell should take
1 Virtual path (VP) switching ndash channels within each VP remain with the VP
2 Virtual path and channel (VPC) switching ndash a channel from one VP may pass into
another VP
IXSDHSONET
Synchronous Optical Network (SONET)
Developed by ANSI
Synchronous Digital Hierarchy (SDH)
Developed by ITU-T
SONETSDH
The two are nearly identical ANSI and ITU-T defined standards that arefundamentally similar and ultimately compatible
Is a synchronous network a single clock is used to handle the timing of
transmissions and equipment across the entire network
SONET
It defines the hierarchy of signals called synchronous transport signals (STS)
Optical carrier (OC) levels are the implementation of STS
SONETSDH Rates
STS OC Rate (Mbps) STM
STS-1 OC-1 5184
STS-3 OC-3 15552 STM-1
STS-9 OC-9 46656 STM-3
STS-12 OC-12 62208 STM-4
STS-18 OC-18 93312 STM-6
STS-24 OC-24 124416 STM-8
STS-36 OC-36 186623 STM-12
STS-48 OC-48 248832 STM-16
STS-96 OC-96 497664 STM-32
STS-192 OC-192 995328 STM-64
STM-synchronous transport module
SONET Four Layers
1 Photonic layer is the lowest and performs physical layer activities
A frame at the photonic layer for STS-1 consists of 6480 bits (8000 framessec)
2-4 Section Line and Path layers correspond to the OSI modelrsquos datalink layer Eachof these layers is responsible for signal transfer across a specific portion of the
1 STS multiplexer combines several optical signals to make an STS signal2 Regenerator removes noise from optical signal
3 Adddrop multiplexer adds STS signals from different paths and removes STS signal
from a path
XTCPIP
Transmission Control ProtocolInternetworking Protocol (TCPIP)
Is a set of rules and procedures that governs the exchange of messages in an
internetwork Originally developed as a protocol for networks that wanted to be connected to
ARPANET a US Department of Defense project now known as Internet
Is a five-layer protocol suite whose bottom four layers match the OSI model fairly
closely The highest level the application layer corresponds to OSIrsquos top threelayers
Internet Protocol (IP) Is defined at the network layer
Unreliable and connectionless Is basically the set of rules for one network communicating with any other To be part of internet organization needs an internet network number unique
number to be included in any packet sent out of the network onto the internet
IP packet is known as datagram consists of a variable header and a variable data
field
IP Address
Uniquely defines the connection of a host to its network The host with more than
one IP address is multi-homed host
IP Addressing
32 bit binary number usually represented as 4 decimal values Equivalent to 4 octets ( 8 bits each decimal value ) Dotted decimal notation Consists of 2 parts the network and the node
Network ndash identifier of particular network on the internet
Host ndash identifier of a particular device which can be a server or a
Standby indicator Pin 36 provides the confirmation signal from the DCE in response to
select standby (pin 32)
Send common Pin 37 provides a common signal return line for unbalanced circuits from
the DTE to the DCE
Electrical Specifications
bull EIA 449 uses two other standards to define its electrical specifications
RS-423 (for unbalanced circuits) and RS-422 (for balanced circuits)
RS-423 Unbalanced Mode
bull An unbalanced circuit specification meaning that it defines only one linefor propagating a signal All signals in this standard use a common return
(or ground) to complete the circuit
RS-422 Balanced Mode
bull A balanced circuit specification meaning that it defines two lines for the propagation of each signal Signals again use a common return (or ground)
for the return of the signal In balanced mode EIA-449 utilizes both pinsin each Category I but does not use the Category II pins The ratio of data
rate to distance is much higher that that of the unbalanced standard or of
EIA-232 10 Mbps for transmission of 40 feet bull In balanced mode two lines carry the same transmission it do not carry
identical signals The signal on one line is the complement of the signal
on the other When plotted the complement looks like a mirror image ofthe original signal Instead of listening to either actual signal the receiver
detects the differences between the two This mechanism makes a balanced circuit less susceptible to noise than an unbalanced circuit and
improves performance
EIA-530
bull A version of EIA-449 that uses DB-25 pins
bull The pin functions of EIA-530 are essentially the same of EIA-449
Category I plus three pins from Category II (the loopback circuits) Other pins in EIA-232 are omitted in EIA-530 such as ring indicator signal
quality detector and data signal rate selector
X21
bull Is an interface standard designed by ITU-T to address many problems
existing in the EIA interfaces and at the same time paves the way for alldigital communications
bull A large proportion of the circuits in the EIA interfaces are used forcontrol since these are necessary to implement control functions as
separate signals With a separate line control information is represented
only by positive and negative voltages But if control signals are encoded
using a meaningful control characters from a system such as ASCII it can be transmitted over data lines
bull X21 eliminates most of the control circuits of the EIA standards and
instead directs its traffic over the data circuits To make this consolidationof functionality possible both the DTE and the DCE must have added
circuit logic that enables them to transform the control codes into bit
streams that can be sent over the data line Both also need additional logicto discriminate between control information and data upon receipt
bull Design of X21 allows not only to use fewer pins but also to be used in
digital telecommunications where control information is sent from deviceto device over a network rather than just between a DTE and a DCE
bull X21 is useful both as an interface to connect digital computers to analogdevices such as modems and as a connector between digital computers and
digital interfaces such as ISDN and X25
Byte Timing
bull Another advantage offered by X21 is that of timing lines to control bytesynchronization in addition to the bit synchronization provided by the EIA
standards By adding a byte timing pulse improves the overall
synchronization of transmissions
Control and indication
bull Pins 3 and 5 of the DB-15 connector are used for the initial handshake or
agreement to begin transmitting Pin 3 is the equivalent of request to send
Pin 5 is the equivalent of clear to send
MODEMbull Modem stands for modulatordemodulator
bull A modulator converts a digital to an analog signalbull A demodulator converts an analog signal to a digital signal
bull The series of 1s and 0s are transformed through the mechanism of ASK
FSK PSK and QAM
Transmission Rate
Bandwidth
bull Every line has upper limit and a lower limit on the frequencies of the
signals it carry this limited range is called the bandwidth
It handles connection establishment and termination data transfer
and packet creation protocols Two types of PLP packets information and control
Up to 4096 channels may be multiplexed at the PLP level Specifies protocols to handle resizing of messages
FRAME RELAY LAYERSbull A technology that operates only at the physical and datalink layers No protocol is
specified for the physical layer the choice is up to the user
bull Eliminates the extensive error checking necessary in X25 protocol
bull It uses simplified version of HDLC protocol in the datalink layerbull It uses routing and switching functions of the datalink layers Frames not packets
are switched
bull It uses PVCs (permanent virtual circuits) Identified through a DLCI (dalta linkconnection identifier)
bull A switch in frame relay performs error checking and routing Error correction is
left to the other protocols at the higher layers
bull Flow control is handled through setting the BECN (backwards explicit congestionnotification) and FECN (forward explicit congestion notification) in the address
field of the frame
bull
ASYNCHRONOUS TRANSFER MODE (ATM)
bull Is the cell relay protocol designed by the ATM forum and adopted by theITU-T
bull In ATM some software functions have moved to hardware this can
increase the data rate
Terms
Cell is the data packet is called a and is composed of 53 bytes (5 bytes of header and 48 bytes of payload) Because each cell is the same size and all are relatively small delay
and other problems associated with multiplexing different sized packets are avoided
A cell network is based on permanent virtual circuit (PVC) routing
bull Virtual Path Identifier (VPI) specifies the path a cell should take
1 Virtual path (VP) switching ndash channels within each VP remain with the VP
2 Virtual path and channel (VPC) switching ndash a channel from one VP may pass into
another VP
IXSDHSONET
Synchronous Optical Network (SONET)
Developed by ANSI
Synchronous Digital Hierarchy (SDH)
Developed by ITU-T
SONETSDH
The two are nearly identical ANSI and ITU-T defined standards that arefundamentally similar and ultimately compatible
Is a synchronous network a single clock is used to handle the timing of
transmissions and equipment across the entire network
SONET
It defines the hierarchy of signals called synchronous transport signals (STS)
Optical carrier (OC) levels are the implementation of STS
SONETSDH Rates
STS OC Rate (Mbps) STM
STS-1 OC-1 5184
STS-3 OC-3 15552 STM-1
STS-9 OC-9 46656 STM-3
STS-12 OC-12 62208 STM-4
STS-18 OC-18 93312 STM-6
STS-24 OC-24 124416 STM-8
STS-36 OC-36 186623 STM-12
STS-48 OC-48 248832 STM-16
STS-96 OC-96 497664 STM-32
STS-192 OC-192 995328 STM-64
STM-synchronous transport module
SONET Four Layers
1 Photonic layer is the lowest and performs physical layer activities
A frame at the photonic layer for STS-1 consists of 6480 bits (8000 framessec)
2-4 Section Line and Path layers correspond to the OSI modelrsquos datalink layer Eachof these layers is responsible for signal transfer across a specific portion of the
1 STS multiplexer combines several optical signals to make an STS signal2 Regenerator removes noise from optical signal
3 Adddrop multiplexer adds STS signals from different paths and removes STS signal
from a path
XTCPIP
Transmission Control ProtocolInternetworking Protocol (TCPIP)
Is a set of rules and procedures that governs the exchange of messages in an
internetwork Originally developed as a protocol for networks that wanted to be connected to
ARPANET a US Department of Defense project now known as Internet
Is a five-layer protocol suite whose bottom four layers match the OSI model fairly
closely The highest level the application layer corresponds to OSIrsquos top threelayers
Internet Protocol (IP) Is defined at the network layer
Unreliable and connectionless Is basically the set of rules for one network communicating with any other To be part of internet organization needs an internet network number unique
number to be included in any packet sent out of the network onto the internet
IP packet is known as datagram consists of a variable header and a variable data
field
IP Address
Uniquely defines the connection of a host to its network The host with more than
one IP address is multi-homed host
IP Addressing
32 bit binary number usually represented as 4 decimal values Equivalent to 4 octets ( 8 bits each decimal value ) Dotted decimal notation Consists of 2 parts the network and the node
Network ndash identifier of particular network on the internet
Host ndash identifier of a particular device which can be a server or a
Standby indicator Pin 36 provides the confirmation signal from the DCE in response to
select standby (pin 32)
Send common Pin 37 provides a common signal return line for unbalanced circuits from
the DTE to the DCE
Electrical Specifications
bull EIA 449 uses two other standards to define its electrical specifications
RS-423 (for unbalanced circuits) and RS-422 (for balanced circuits)
RS-423 Unbalanced Mode
bull An unbalanced circuit specification meaning that it defines only one linefor propagating a signal All signals in this standard use a common return
(or ground) to complete the circuit
RS-422 Balanced Mode
bull A balanced circuit specification meaning that it defines two lines for the propagation of each signal Signals again use a common return (or ground)
for the return of the signal In balanced mode EIA-449 utilizes both pinsin each Category I but does not use the Category II pins The ratio of data
rate to distance is much higher that that of the unbalanced standard or of
EIA-232 10 Mbps for transmission of 40 feet bull In balanced mode two lines carry the same transmission it do not carry
identical signals The signal on one line is the complement of the signal
on the other When plotted the complement looks like a mirror image ofthe original signal Instead of listening to either actual signal the receiver
detects the differences between the two This mechanism makes a balanced circuit less susceptible to noise than an unbalanced circuit and
improves performance
EIA-530
bull A version of EIA-449 that uses DB-25 pins
bull The pin functions of EIA-530 are essentially the same of EIA-449
Category I plus three pins from Category II (the loopback circuits) Other pins in EIA-232 are omitted in EIA-530 such as ring indicator signal
quality detector and data signal rate selector
X21
bull Is an interface standard designed by ITU-T to address many problems
existing in the EIA interfaces and at the same time paves the way for alldigital communications
bull A large proportion of the circuits in the EIA interfaces are used forcontrol since these are necessary to implement control functions as
separate signals With a separate line control information is represented
only by positive and negative voltages But if control signals are encoded
using a meaningful control characters from a system such as ASCII it can be transmitted over data lines
bull X21 eliminates most of the control circuits of the EIA standards and
instead directs its traffic over the data circuits To make this consolidationof functionality possible both the DTE and the DCE must have added
circuit logic that enables them to transform the control codes into bit
streams that can be sent over the data line Both also need additional logicto discriminate between control information and data upon receipt
bull Design of X21 allows not only to use fewer pins but also to be used in
digital telecommunications where control information is sent from deviceto device over a network rather than just between a DTE and a DCE
bull X21 is useful both as an interface to connect digital computers to analogdevices such as modems and as a connector between digital computers and
digital interfaces such as ISDN and X25
Byte Timing
bull Another advantage offered by X21 is that of timing lines to control bytesynchronization in addition to the bit synchronization provided by the EIA
standards By adding a byte timing pulse improves the overall
synchronization of transmissions
Control and indication
bull Pins 3 and 5 of the DB-15 connector are used for the initial handshake or
agreement to begin transmitting Pin 3 is the equivalent of request to send
Pin 5 is the equivalent of clear to send
MODEMbull Modem stands for modulatordemodulator
bull A modulator converts a digital to an analog signalbull A demodulator converts an analog signal to a digital signal
bull The series of 1s and 0s are transformed through the mechanism of ASK
FSK PSK and QAM
Transmission Rate
Bandwidth
bull Every line has upper limit and a lower limit on the frequencies of the
signals it carry this limited range is called the bandwidth
It handles connection establishment and termination data transfer
and packet creation protocols Two types of PLP packets information and control
Up to 4096 channels may be multiplexed at the PLP level Specifies protocols to handle resizing of messages
FRAME RELAY LAYERSbull A technology that operates only at the physical and datalink layers No protocol is
specified for the physical layer the choice is up to the user
bull Eliminates the extensive error checking necessary in X25 protocol
bull It uses simplified version of HDLC protocol in the datalink layerbull It uses routing and switching functions of the datalink layers Frames not packets
are switched
bull It uses PVCs (permanent virtual circuits) Identified through a DLCI (dalta linkconnection identifier)
bull A switch in frame relay performs error checking and routing Error correction is
left to the other protocols at the higher layers
bull Flow control is handled through setting the BECN (backwards explicit congestionnotification) and FECN (forward explicit congestion notification) in the address
field of the frame
bull
ASYNCHRONOUS TRANSFER MODE (ATM)
bull Is the cell relay protocol designed by the ATM forum and adopted by theITU-T
bull In ATM some software functions have moved to hardware this can
increase the data rate
Terms
Cell is the data packet is called a and is composed of 53 bytes (5 bytes of header and 48 bytes of payload) Because each cell is the same size and all are relatively small delay
and other problems associated with multiplexing different sized packets are avoided
A cell network is based on permanent virtual circuit (PVC) routing
bull Virtual Path Identifier (VPI) specifies the path a cell should take
1 Virtual path (VP) switching ndash channels within each VP remain with the VP
2 Virtual path and channel (VPC) switching ndash a channel from one VP may pass into
another VP
IXSDHSONET
Synchronous Optical Network (SONET)
Developed by ANSI
Synchronous Digital Hierarchy (SDH)
Developed by ITU-T
SONETSDH
The two are nearly identical ANSI and ITU-T defined standards that arefundamentally similar and ultimately compatible
Is a synchronous network a single clock is used to handle the timing of
transmissions and equipment across the entire network
SONET
It defines the hierarchy of signals called synchronous transport signals (STS)
Optical carrier (OC) levels are the implementation of STS
SONETSDH Rates
STS OC Rate (Mbps) STM
STS-1 OC-1 5184
STS-3 OC-3 15552 STM-1
STS-9 OC-9 46656 STM-3
STS-12 OC-12 62208 STM-4
STS-18 OC-18 93312 STM-6
STS-24 OC-24 124416 STM-8
STS-36 OC-36 186623 STM-12
STS-48 OC-48 248832 STM-16
STS-96 OC-96 497664 STM-32
STS-192 OC-192 995328 STM-64
STM-synchronous transport module
SONET Four Layers
1 Photonic layer is the lowest and performs physical layer activities
A frame at the photonic layer for STS-1 consists of 6480 bits (8000 framessec)
2-4 Section Line and Path layers correspond to the OSI modelrsquos datalink layer Eachof these layers is responsible for signal transfer across a specific portion of the
1 STS multiplexer combines several optical signals to make an STS signal2 Regenerator removes noise from optical signal
3 Adddrop multiplexer adds STS signals from different paths and removes STS signal
from a path
XTCPIP
Transmission Control ProtocolInternetworking Protocol (TCPIP)
Is a set of rules and procedures that governs the exchange of messages in an
internetwork Originally developed as a protocol for networks that wanted to be connected to
ARPANET a US Department of Defense project now known as Internet
Is a five-layer protocol suite whose bottom four layers match the OSI model fairly
closely The highest level the application layer corresponds to OSIrsquos top threelayers
Internet Protocol (IP) Is defined at the network layer
Unreliable and connectionless Is basically the set of rules for one network communicating with any other To be part of internet organization needs an internet network number unique
number to be included in any packet sent out of the network onto the internet
IP packet is known as datagram consists of a variable header and a variable data
field
IP Address
Uniquely defines the connection of a host to its network The host with more than
one IP address is multi-homed host
IP Addressing
32 bit binary number usually represented as 4 decimal values Equivalent to 4 octets ( 8 bits each decimal value ) Dotted decimal notation Consists of 2 parts the network and the node
Network ndash identifier of particular network on the internet
Host ndash identifier of a particular device which can be a server or a
Standby indicator Pin 36 provides the confirmation signal from the DCE in response to
select standby (pin 32)
Send common Pin 37 provides a common signal return line for unbalanced circuits from
the DTE to the DCE
Electrical Specifications
bull EIA 449 uses two other standards to define its electrical specifications
RS-423 (for unbalanced circuits) and RS-422 (for balanced circuits)
RS-423 Unbalanced Mode
bull An unbalanced circuit specification meaning that it defines only one linefor propagating a signal All signals in this standard use a common return
(or ground) to complete the circuit
RS-422 Balanced Mode
bull A balanced circuit specification meaning that it defines two lines for the propagation of each signal Signals again use a common return (or ground)
for the return of the signal In balanced mode EIA-449 utilizes both pinsin each Category I but does not use the Category II pins The ratio of data
rate to distance is much higher that that of the unbalanced standard or of
EIA-232 10 Mbps for transmission of 40 feet bull In balanced mode two lines carry the same transmission it do not carry
identical signals The signal on one line is the complement of the signal
on the other When plotted the complement looks like a mirror image ofthe original signal Instead of listening to either actual signal the receiver
detects the differences between the two This mechanism makes a balanced circuit less susceptible to noise than an unbalanced circuit and
improves performance
EIA-530
bull A version of EIA-449 that uses DB-25 pins
bull The pin functions of EIA-530 are essentially the same of EIA-449
Category I plus three pins from Category II (the loopback circuits) Other pins in EIA-232 are omitted in EIA-530 such as ring indicator signal
quality detector and data signal rate selector
X21
bull Is an interface standard designed by ITU-T to address many problems
existing in the EIA interfaces and at the same time paves the way for alldigital communications
bull A large proportion of the circuits in the EIA interfaces are used forcontrol since these are necessary to implement control functions as
separate signals With a separate line control information is represented
only by positive and negative voltages But if control signals are encoded
using a meaningful control characters from a system such as ASCII it can be transmitted over data lines
bull X21 eliminates most of the control circuits of the EIA standards and
instead directs its traffic over the data circuits To make this consolidationof functionality possible both the DTE and the DCE must have added
circuit logic that enables them to transform the control codes into bit
streams that can be sent over the data line Both also need additional logicto discriminate between control information and data upon receipt
bull Design of X21 allows not only to use fewer pins but also to be used in
digital telecommunications where control information is sent from deviceto device over a network rather than just between a DTE and a DCE
bull X21 is useful both as an interface to connect digital computers to analogdevices such as modems and as a connector between digital computers and
digital interfaces such as ISDN and X25
Byte Timing
bull Another advantage offered by X21 is that of timing lines to control bytesynchronization in addition to the bit synchronization provided by the EIA
standards By adding a byte timing pulse improves the overall
synchronization of transmissions
Control and indication
bull Pins 3 and 5 of the DB-15 connector are used for the initial handshake or
agreement to begin transmitting Pin 3 is the equivalent of request to send
Pin 5 is the equivalent of clear to send
MODEMbull Modem stands for modulatordemodulator
bull A modulator converts a digital to an analog signalbull A demodulator converts an analog signal to a digital signal
bull The series of 1s and 0s are transformed through the mechanism of ASK
FSK PSK and QAM
Transmission Rate
Bandwidth
bull Every line has upper limit and a lower limit on the frequencies of the
signals it carry this limited range is called the bandwidth
It handles connection establishment and termination data transfer
and packet creation protocols Two types of PLP packets information and control
Up to 4096 channels may be multiplexed at the PLP level Specifies protocols to handle resizing of messages
FRAME RELAY LAYERSbull A technology that operates only at the physical and datalink layers No protocol is
specified for the physical layer the choice is up to the user
bull Eliminates the extensive error checking necessary in X25 protocol
bull It uses simplified version of HDLC protocol in the datalink layerbull It uses routing and switching functions of the datalink layers Frames not packets
are switched
bull It uses PVCs (permanent virtual circuits) Identified through a DLCI (dalta linkconnection identifier)
bull A switch in frame relay performs error checking and routing Error correction is
left to the other protocols at the higher layers
bull Flow control is handled through setting the BECN (backwards explicit congestionnotification) and FECN (forward explicit congestion notification) in the address
field of the frame
bull
ASYNCHRONOUS TRANSFER MODE (ATM)
bull Is the cell relay protocol designed by the ATM forum and adopted by theITU-T
bull In ATM some software functions have moved to hardware this can
increase the data rate
Terms
Cell is the data packet is called a and is composed of 53 bytes (5 bytes of header and 48 bytes of payload) Because each cell is the same size and all are relatively small delay
and other problems associated with multiplexing different sized packets are avoided
A cell network is based on permanent virtual circuit (PVC) routing
bull Virtual Path Identifier (VPI) specifies the path a cell should take
1 Virtual path (VP) switching ndash channels within each VP remain with the VP
2 Virtual path and channel (VPC) switching ndash a channel from one VP may pass into
another VP
IXSDHSONET
Synchronous Optical Network (SONET)
Developed by ANSI
Synchronous Digital Hierarchy (SDH)
Developed by ITU-T
SONETSDH
The two are nearly identical ANSI and ITU-T defined standards that arefundamentally similar and ultimately compatible
Is a synchronous network a single clock is used to handle the timing of
transmissions and equipment across the entire network
SONET
It defines the hierarchy of signals called synchronous transport signals (STS)
Optical carrier (OC) levels are the implementation of STS
SONETSDH Rates
STS OC Rate (Mbps) STM
STS-1 OC-1 5184
STS-3 OC-3 15552 STM-1
STS-9 OC-9 46656 STM-3
STS-12 OC-12 62208 STM-4
STS-18 OC-18 93312 STM-6
STS-24 OC-24 124416 STM-8
STS-36 OC-36 186623 STM-12
STS-48 OC-48 248832 STM-16
STS-96 OC-96 497664 STM-32
STS-192 OC-192 995328 STM-64
STM-synchronous transport module
SONET Four Layers
1 Photonic layer is the lowest and performs physical layer activities
A frame at the photonic layer for STS-1 consists of 6480 bits (8000 framessec)
2-4 Section Line and Path layers correspond to the OSI modelrsquos datalink layer Eachof these layers is responsible for signal transfer across a specific portion of the
1 STS multiplexer combines several optical signals to make an STS signal2 Regenerator removes noise from optical signal
3 Adddrop multiplexer adds STS signals from different paths and removes STS signal
from a path
XTCPIP
Transmission Control ProtocolInternetworking Protocol (TCPIP)
Is a set of rules and procedures that governs the exchange of messages in an
internetwork Originally developed as a protocol for networks that wanted to be connected to
ARPANET a US Department of Defense project now known as Internet
Is a five-layer protocol suite whose bottom four layers match the OSI model fairly
closely The highest level the application layer corresponds to OSIrsquos top threelayers
Internet Protocol (IP) Is defined at the network layer
Unreliable and connectionless Is basically the set of rules for one network communicating with any other To be part of internet organization needs an internet network number unique
number to be included in any packet sent out of the network onto the internet
IP packet is known as datagram consists of a variable header and a variable data
field
IP Address
Uniquely defines the connection of a host to its network The host with more than
one IP address is multi-homed host
IP Addressing
32 bit binary number usually represented as 4 decimal values Equivalent to 4 octets ( 8 bits each decimal value ) Dotted decimal notation Consists of 2 parts the network and the node
Network ndash identifier of particular network on the internet
Host ndash identifier of a particular device which can be a server or a
Standby indicator Pin 36 provides the confirmation signal from the DCE in response to
select standby (pin 32)
Send common Pin 37 provides a common signal return line for unbalanced circuits from
the DTE to the DCE
Electrical Specifications
bull EIA 449 uses two other standards to define its electrical specifications
RS-423 (for unbalanced circuits) and RS-422 (for balanced circuits)
RS-423 Unbalanced Mode
bull An unbalanced circuit specification meaning that it defines only one linefor propagating a signal All signals in this standard use a common return
(or ground) to complete the circuit
RS-422 Balanced Mode
bull A balanced circuit specification meaning that it defines two lines for the propagation of each signal Signals again use a common return (or ground)
for the return of the signal In balanced mode EIA-449 utilizes both pinsin each Category I but does not use the Category II pins The ratio of data
rate to distance is much higher that that of the unbalanced standard or of
EIA-232 10 Mbps for transmission of 40 feet bull In balanced mode two lines carry the same transmission it do not carry
identical signals The signal on one line is the complement of the signal
on the other When plotted the complement looks like a mirror image ofthe original signal Instead of listening to either actual signal the receiver
detects the differences between the two This mechanism makes a balanced circuit less susceptible to noise than an unbalanced circuit and
improves performance
EIA-530
bull A version of EIA-449 that uses DB-25 pins
bull The pin functions of EIA-530 are essentially the same of EIA-449
Category I plus three pins from Category II (the loopback circuits) Other pins in EIA-232 are omitted in EIA-530 such as ring indicator signal
quality detector and data signal rate selector
X21
bull Is an interface standard designed by ITU-T to address many problems
existing in the EIA interfaces and at the same time paves the way for alldigital communications
bull A large proportion of the circuits in the EIA interfaces are used forcontrol since these are necessary to implement control functions as
separate signals With a separate line control information is represented
only by positive and negative voltages But if control signals are encoded
using a meaningful control characters from a system such as ASCII it can be transmitted over data lines
bull X21 eliminates most of the control circuits of the EIA standards and
instead directs its traffic over the data circuits To make this consolidationof functionality possible both the DTE and the DCE must have added
circuit logic that enables them to transform the control codes into bit
streams that can be sent over the data line Both also need additional logicto discriminate between control information and data upon receipt
bull Design of X21 allows not only to use fewer pins but also to be used in
digital telecommunications where control information is sent from deviceto device over a network rather than just between a DTE and a DCE
bull X21 is useful both as an interface to connect digital computers to analogdevices such as modems and as a connector between digital computers and
digital interfaces such as ISDN and X25
Byte Timing
bull Another advantage offered by X21 is that of timing lines to control bytesynchronization in addition to the bit synchronization provided by the EIA
standards By adding a byte timing pulse improves the overall
synchronization of transmissions
Control and indication
bull Pins 3 and 5 of the DB-15 connector are used for the initial handshake or
agreement to begin transmitting Pin 3 is the equivalent of request to send
Pin 5 is the equivalent of clear to send
MODEMbull Modem stands for modulatordemodulator
bull A modulator converts a digital to an analog signalbull A demodulator converts an analog signal to a digital signal
bull The series of 1s and 0s are transformed through the mechanism of ASK
FSK PSK and QAM
Transmission Rate
Bandwidth
bull Every line has upper limit and a lower limit on the frequencies of the
signals it carry this limited range is called the bandwidth
It handles connection establishment and termination data transfer
and packet creation protocols Two types of PLP packets information and control
Up to 4096 channels may be multiplexed at the PLP level Specifies protocols to handle resizing of messages
FRAME RELAY LAYERSbull A technology that operates only at the physical and datalink layers No protocol is
specified for the physical layer the choice is up to the user
bull Eliminates the extensive error checking necessary in X25 protocol
bull It uses simplified version of HDLC protocol in the datalink layerbull It uses routing and switching functions of the datalink layers Frames not packets
are switched
bull It uses PVCs (permanent virtual circuits) Identified through a DLCI (dalta linkconnection identifier)
bull A switch in frame relay performs error checking and routing Error correction is
left to the other protocols at the higher layers
bull Flow control is handled through setting the BECN (backwards explicit congestionnotification) and FECN (forward explicit congestion notification) in the address
field of the frame
bull
ASYNCHRONOUS TRANSFER MODE (ATM)
bull Is the cell relay protocol designed by the ATM forum and adopted by theITU-T
bull In ATM some software functions have moved to hardware this can
increase the data rate
Terms
Cell is the data packet is called a and is composed of 53 bytes (5 bytes of header and 48 bytes of payload) Because each cell is the same size and all are relatively small delay
and other problems associated with multiplexing different sized packets are avoided
A cell network is based on permanent virtual circuit (PVC) routing
bull Virtual Path Identifier (VPI) specifies the path a cell should take
1 Virtual path (VP) switching ndash channels within each VP remain with the VP
2 Virtual path and channel (VPC) switching ndash a channel from one VP may pass into
another VP
IXSDHSONET
Synchronous Optical Network (SONET)
Developed by ANSI
Synchronous Digital Hierarchy (SDH)
Developed by ITU-T
SONETSDH
The two are nearly identical ANSI and ITU-T defined standards that arefundamentally similar and ultimately compatible
Is a synchronous network a single clock is used to handle the timing of
transmissions and equipment across the entire network
SONET
It defines the hierarchy of signals called synchronous transport signals (STS)
Optical carrier (OC) levels are the implementation of STS
SONETSDH Rates
STS OC Rate (Mbps) STM
STS-1 OC-1 5184
STS-3 OC-3 15552 STM-1
STS-9 OC-9 46656 STM-3
STS-12 OC-12 62208 STM-4
STS-18 OC-18 93312 STM-6
STS-24 OC-24 124416 STM-8
STS-36 OC-36 186623 STM-12
STS-48 OC-48 248832 STM-16
STS-96 OC-96 497664 STM-32
STS-192 OC-192 995328 STM-64
STM-synchronous transport module
SONET Four Layers
1 Photonic layer is the lowest and performs physical layer activities
A frame at the photonic layer for STS-1 consists of 6480 bits (8000 framessec)
2-4 Section Line and Path layers correspond to the OSI modelrsquos datalink layer Eachof these layers is responsible for signal transfer across a specific portion of the
1 STS multiplexer combines several optical signals to make an STS signal2 Regenerator removes noise from optical signal
3 Adddrop multiplexer adds STS signals from different paths and removes STS signal
from a path
XTCPIP
Transmission Control ProtocolInternetworking Protocol (TCPIP)
Is a set of rules and procedures that governs the exchange of messages in an
internetwork Originally developed as a protocol for networks that wanted to be connected to
ARPANET a US Department of Defense project now known as Internet
Is a five-layer protocol suite whose bottom four layers match the OSI model fairly
closely The highest level the application layer corresponds to OSIrsquos top threelayers
Internet Protocol (IP) Is defined at the network layer
Unreliable and connectionless Is basically the set of rules for one network communicating with any other To be part of internet organization needs an internet network number unique
number to be included in any packet sent out of the network onto the internet
IP packet is known as datagram consists of a variable header and a variable data
field
IP Address
Uniquely defines the connection of a host to its network The host with more than
one IP address is multi-homed host
IP Addressing
32 bit binary number usually represented as 4 decimal values Equivalent to 4 octets ( 8 bits each decimal value ) Dotted decimal notation Consists of 2 parts the network and the node
Network ndash identifier of particular network on the internet
Host ndash identifier of a particular device which can be a server or a
Standby indicator Pin 36 provides the confirmation signal from the DCE in response to
select standby (pin 32)
Send common Pin 37 provides a common signal return line for unbalanced circuits from
the DTE to the DCE
Electrical Specifications
bull EIA 449 uses two other standards to define its electrical specifications
RS-423 (for unbalanced circuits) and RS-422 (for balanced circuits)
RS-423 Unbalanced Mode
bull An unbalanced circuit specification meaning that it defines only one linefor propagating a signal All signals in this standard use a common return
(or ground) to complete the circuit
RS-422 Balanced Mode
bull A balanced circuit specification meaning that it defines two lines for the propagation of each signal Signals again use a common return (or ground)
for the return of the signal In balanced mode EIA-449 utilizes both pinsin each Category I but does not use the Category II pins The ratio of data
rate to distance is much higher that that of the unbalanced standard or of
EIA-232 10 Mbps for transmission of 40 feet bull In balanced mode two lines carry the same transmission it do not carry
identical signals The signal on one line is the complement of the signal
on the other When plotted the complement looks like a mirror image ofthe original signal Instead of listening to either actual signal the receiver
detects the differences between the two This mechanism makes a balanced circuit less susceptible to noise than an unbalanced circuit and
improves performance
EIA-530
bull A version of EIA-449 that uses DB-25 pins
bull The pin functions of EIA-530 are essentially the same of EIA-449
Category I plus three pins from Category II (the loopback circuits) Other pins in EIA-232 are omitted in EIA-530 such as ring indicator signal
quality detector and data signal rate selector
X21
bull Is an interface standard designed by ITU-T to address many problems
existing in the EIA interfaces and at the same time paves the way for alldigital communications
bull A large proportion of the circuits in the EIA interfaces are used forcontrol since these are necessary to implement control functions as
separate signals With a separate line control information is represented
only by positive and negative voltages But if control signals are encoded
using a meaningful control characters from a system such as ASCII it can be transmitted over data lines
bull X21 eliminates most of the control circuits of the EIA standards and
instead directs its traffic over the data circuits To make this consolidationof functionality possible both the DTE and the DCE must have added
circuit logic that enables them to transform the control codes into bit
streams that can be sent over the data line Both also need additional logicto discriminate between control information and data upon receipt
bull Design of X21 allows not only to use fewer pins but also to be used in
digital telecommunications where control information is sent from deviceto device over a network rather than just between a DTE and a DCE
bull X21 is useful both as an interface to connect digital computers to analogdevices such as modems and as a connector between digital computers and
digital interfaces such as ISDN and X25
Byte Timing
bull Another advantage offered by X21 is that of timing lines to control bytesynchronization in addition to the bit synchronization provided by the EIA
standards By adding a byte timing pulse improves the overall
synchronization of transmissions
Control and indication
bull Pins 3 and 5 of the DB-15 connector are used for the initial handshake or
agreement to begin transmitting Pin 3 is the equivalent of request to send
Pin 5 is the equivalent of clear to send
MODEMbull Modem stands for modulatordemodulator
bull A modulator converts a digital to an analog signalbull A demodulator converts an analog signal to a digital signal
bull The series of 1s and 0s are transformed through the mechanism of ASK
FSK PSK and QAM
Transmission Rate
Bandwidth
bull Every line has upper limit and a lower limit on the frequencies of the
signals it carry this limited range is called the bandwidth
It handles connection establishment and termination data transfer
and packet creation protocols Two types of PLP packets information and control
Up to 4096 channels may be multiplexed at the PLP level Specifies protocols to handle resizing of messages
FRAME RELAY LAYERSbull A technology that operates only at the physical and datalink layers No protocol is
specified for the physical layer the choice is up to the user
bull Eliminates the extensive error checking necessary in X25 protocol
bull It uses simplified version of HDLC protocol in the datalink layerbull It uses routing and switching functions of the datalink layers Frames not packets
are switched
bull It uses PVCs (permanent virtual circuits) Identified through a DLCI (dalta linkconnection identifier)
bull A switch in frame relay performs error checking and routing Error correction is
left to the other protocols at the higher layers
bull Flow control is handled through setting the BECN (backwards explicit congestionnotification) and FECN (forward explicit congestion notification) in the address
field of the frame
bull
ASYNCHRONOUS TRANSFER MODE (ATM)
bull Is the cell relay protocol designed by the ATM forum and adopted by theITU-T
bull In ATM some software functions have moved to hardware this can
increase the data rate
Terms
Cell is the data packet is called a and is composed of 53 bytes (5 bytes of header and 48 bytes of payload) Because each cell is the same size and all are relatively small delay
and other problems associated with multiplexing different sized packets are avoided
A cell network is based on permanent virtual circuit (PVC) routing
bull Virtual Path Identifier (VPI) specifies the path a cell should take
1 Virtual path (VP) switching ndash channels within each VP remain with the VP
2 Virtual path and channel (VPC) switching ndash a channel from one VP may pass into
another VP
IXSDHSONET
Synchronous Optical Network (SONET)
Developed by ANSI
Synchronous Digital Hierarchy (SDH)
Developed by ITU-T
SONETSDH
The two are nearly identical ANSI and ITU-T defined standards that arefundamentally similar and ultimately compatible
Is a synchronous network a single clock is used to handle the timing of
transmissions and equipment across the entire network
SONET
It defines the hierarchy of signals called synchronous transport signals (STS)
Optical carrier (OC) levels are the implementation of STS
SONETSDH Rates
STS OC Rate (Mbps) STM
STS-1 OC-1 5184
STS-3 OC-3 15552 STM-1
STS-9 OC-9 46656 STM-3
STS-12 OC-12 62208 STM-4
STS-18 OC-18 93312 STM-6
STS-24 OC-24 124416 STM-8
STS-36 OC-36 186623 STM-12
STS-48 OC-48 248832 STM-16
STS-96 OC-96 497664 STM-32
STS-192 OC-192 995328 STM-64
STM-synchronous transport module
SONET Four Layers
1 Photonic layer is the lowest and performs physical layer activities
A frame at the photonic layer for STS-1 consists of 6480 bits (8000 framessec)
2-4 Section Line and Path layers correspond to the OSI modelrsquos datalink layer Eachof these layers is responsible for signal transfer across a specific portion of the
1 STS multiplexer combines several optical signals to make an STS signal2 Regenerator removes noise from optical signal
3 Adddrop multiplexer adds STS signals from different paths and removes STS signal
from a path
XTCPIP
Transmission Control ProtocolInternetworking Protocol (TCPIP)
Is a set of rules and procedures that governs the exchange of messages in an
internetwork Originally developed as a protocol for networks that wanted to be connected to
ARPANET a US Department of Defense project now known as Internet
Is a five-layer protocol suite whose bottom four layers match the OSI model fairly
closely The highest level the application layer corresponds to OSIrsquos top threelayers
Internet Protocol (IP) Is defined at the network layer
Unreliable and connectionless Is basically the set of rules for one network communicating with any other To be part of internet organization needs an internet network number unique
number to be included in any packet sent out of the network onto the internet
IP packet is known as datagram consists of a variable header and a variable data
field
IP Address
Uniquely defines the connection of a host to its network The host with more than
one IP address is multi-homed host
IP Addressing
32 bit binary number usually represented as 4 decimal values Equivalent to 4 octets ( 8 bits each decimal value ) Dotted decimal notation Consists of 2 parts the network and the node
Network ndash identifier of particular network on the internet
Host ndash identifier of a particular device which can be a server or a
Standby indicator Pin 36 provides the confirmation signal from the DCE in response to
select standby (pin 32)
Send common Pin 37 provides a common signal return line for unbalanced circuits from
the DTE to the DCE
Electrical Specifications
bull EIA 449 uses two other standards to define its electrical specifications
RS-423 (for unbalanced circuits) and RS-422 (for balanced circuits)
RS-423 Unbalanced Mode
bull An unbalanced circuit specification meaning that it defines only one linefor propagating a signal All signals in this standard use a common return
(or ground) to complete the circuit
RS-422 Balanced Mode
bull A balanced circuit specification meaning that it defines two lines for the propagation of each signal Signals again use a common return (or ground)
for the return of the signal In balanced mode EIA-449 utilizes both pinsin each Category I but does not use the Category II pins The ratio of data
rate to distance is much higher that that of the unbalanced standard or of
EIA-232 10 Mbps for transmission of 40 feet bull In balanced mode two lines carry the same transmission it do not carry
identical signals The signal on one line is the complement of the signal
on the other When plotted the complement looks like a mirror image ofthe original signal Instead of listening to either actual signal the receiver
detects the differences between the two This mechanism makes a balanced circuit less susceptible to noise than an unbalanced circuit and
improves performance
EIA-530
bull A version of EIA-449 that uses DB-25 pins
bull The pin functions of EIA-530 are essentially the same of EIA-449
Category I plus three pins from Category II (the loopback circuits) Other pins in EIA-232 are omitted in EIA-530 such as ring indicator signal
quality detector and data signal rate selector
X21
bull Is an interface standard designed by ITU-T to address many problems
existing in the EIA interfaces and at the same time paves the way for alldigital communications
bull A large proportion of the circuits in the EIA interfaces are used forcontrol since these are necessary to implement control functions as
separate signals With a separate line control information is represented
only by positive and negative voltages But if control signals are encoded
using a meaningful control characters from a system such as ASCII it can be transmitted over data lines
bull X21 eliminates most of the control circuits of the EIA standards and
instead directs its traffic over the data circuits To make this consolidationof functionality possible both the DTE and the DCE must have added
circuit logic that enables them to transform the control codes into bit
streams that can be sent over the data line Both also need additional logicto discriminate between control information and data upon receipt
bull Design of X21 allows not only to use fewer pins but also to be used in
digital telecommunications where control information is sent from deviceto device over a network rather than just between a DTE and a DCE
bull X21 is useful both as an interface to connect digital computers to analogdevices such as modems and as a connector between digital computers and
digital interfaces such as ISDN and X25
Byte Timing
bull Another advantage offered by X21 is that of timing lines to control bytesynchronization in addition to the bit synchronization provided by the EIA
standards By adding a byte timing pulse improves the overall
synchronization of transmissions
Control and indication
bull Pins 3 and 5 of the DB-15 connector are used for the initial handshake or
agreement to begin transmitting Pin 3 is the equivalent of request to send
Pin 5 is the equivalent of clear to send
MODEMbull Modem stands for modulatordemodulator
bull A modulator converts a digital to an analog signalbull A demodulator converts an analog signal to a digital signal
bull The series of 1s and 0s are transformed through the mechanism of ASK
FSK PSK and QAM
Transmission Rate
Bandwidth
bull Every line has upper limit and a lower limit on the frequencies of the
signals it carry this limited range is called the bandwidth
It handles connection establishment and termination data transfer
and packet creation protocols Two types of PLP packets information and control
Up to 4096 channels may be multiplexed at the PLP level Specifies protocols to handle resizing of messages
FRAME RELAY LAYERSbull A technology that operates only at the physical and datalink layers No protocol is
specified for the physical layer the choice is up to the user
bull Eliminates the extensive error checking necessary in X25 protocol
bull It uses simplified version of HDLC protocol in the datalink layerbull It uses routing and switching functions of the datalink layers Frames not packets
are switched
bull It uses PVCs (permanent virtual circuits) Identified through a DLCI (dalta linkconnection identifier)
bull A switch in frame relay performs error checking and routing Error correction is
left to the other protocols at the higher layers
bull Flow control is handled through setting the BECN (backwards explicit congestionnotification) and FECN (forward explicit congestion notification) in the address
field of the frame
bull
ASYNCHRONOUS TRANSFER MODE (ATM)
bull Is the cell relay protocol designed by the ATM forum and adopted by theITU-T
bull In ATM some software functions have moved to hardware this can
increase the data rate
Terms
Cell is the data packet is called a and is composed of 53 bytes (5 bytes of header and 48 bytes of payload) Because each cell is the same size and all are relatively small delay
and other problems associated with multiplexing different sized packets are avoided
A cell network is based on permanent virtual circuit (PVC) routing
bull Virtual Path Identifier (VPI) specifies the path a cell should take
1 Virtual path (VP) switching ndash channels within each VP remain with the VP
2 Virtual path and channel (VPC) switching ndash a channel from one VP may pass into
another VP
IXSDHSONET
Synchronous Optical Network (SONET)
Developed by ANSI
Synchronous Digital Hierarchy (SDH)
Developed by ITU-T
SONETSDH
The two are nearly identical ANSI and ITU-T defined standards that arefundamentally similar and ultimately compatible
Is a synchronous network a single clock is used to handle the timing of
transmissions and equipment across the entire network
SONET
It defines the hierarchy of signals called synchronous transport signals (STS)
Optical carrier (OC) levels are the implementation of STS
SONETSDH Rates
STS OC Rate (Mbps) STM
STS-1 OC-1 5184
STS-3 OC-3 15552 STM-1
STS-9 OC-9 46656 STM-3
STS-12 OC-12 62208 STM-4
STS-18 OC-18 93312 STM-6
STS-24 OC-24 124416 STM-8
STS-36 OC-36 186623 STM-12
STS-48 OC-48 248832 STM-16
STS-96 OC-96 497664 STM-32
STS-192 OC-192 995328 STM-64
STM-synchronous transport module
SONET Four Layers
1 Photonic layer is the lowest and performs physical layer activities
A frame at the photonic layer for STS-1 consists of 6480 bits (8000 framessec)
2-4 Section Line and Path layers correspond to the OSI modelrsquos datalink layer Eachof these layers is responsible for signal transfer across a specific portion of the
1 STS multiplexer combines several optical signals to make an STS signal2 Regenerator removes noise from optical signal
3 Adddrop multiplexer adds STS signals from different paths and removes STS signal
from a path
XTCPIP
Transmission Control ProtocolInternetworking Protocol (TCPIP)
Is a set of rules and procedures that governs the exchange of messages in an
internetwork Originally developed as a protocol for networks that wanted to be connected to
ARPANET a US Department of Defense project now known as Internet
Is a five-layer protocol suite whose bottom four layers match the OSI model fairly
closely The highest level the application layer corresponds to OSIrsquos top threelayers
Internet Protocol (IP) Is defined at the network layer
Unreliable and connectionless Is basically the set of rules for one network communicating with any other To be part of internet organization needs an internet network number unique
number to be included in any packet sent out of the network onto the internet
IP packet is known as datagram consists of a variable header and a variable data
field
IP Address
Uniquely defines the connection of a host to its network The host with more than
one IP address is multi-homed host
IP Addressing
32 bit binary number usually represented as 4 decimal values Equivalent to 4 octets ( 8 bits each decimal value ) Dotted decimal notation Consists of 2 parts the network and the node
Network ndash identifier of particular network on the internet
Host ndash identifier of a particular device which can be a server or a
Standby indicator Pin 36 provides the confirmation signal from the DCE in response to
select standby (pin 32)
Send common Pin 37 provides a common signal return line for unbalanced circuits from
the DTE to the DCE
Electrical Specifications
bull EIA 449 uses two other standards to define its electrical specifications
RS-423 (for unbalanced circuits) and RS-422 (for balanced circuits)
RS-423 Unbalanced Mode
bull An unbalanced circuit specification meaning that it defines only one linefor propagating a signal All signals in this standard use a common return
(or ground) to complete the circuit
RS-422 Balanced Mode
bull A balanced circuit specification meaning that it defines two lines for the propagation of each signal Signals again use a common return (or ground)
for the return of the signal In balanced mode EIA-449 utilizes both pinsin each Category I but does not use the Category II pins The ratio of data
rate to distance is much higher that that of the unbalanced standard or of
EIA-232 10 Mbps for transmission of 40 feet bull In balanced mode two lines carry the same transmission it do not carry
identical signals The signal on one line is the complement of the signal
on the other When plotted the complement looks like a mirror image ofthe original signal Instead of listening to either actual signal the receiver
detects the differences between the two This mechanism makes a balanced circuit less susceptible to noise than an unbalanced circuit and
improves performance
EIA-530
bull A version of EIA-449 that uses DB-25 pins
bull The pin functions of EIA-530 are essentially the same of EIA-449
Category I plus three pins from Category II (the loopback circuits) Other pins in EIA-232 are omitted in EIA-530 such as ring indicator signal
quality detector and data signal rate selector
X21
bull Is an interface standard designed by ITU-T to address many problems
existing in the EIA interfaces and at the same time paves the way for alldigital communications
bull A large proportion of the circuits in the EIA interfaces are used forcontrol since these are necessary to implement control functions as
separate signals With a separate line control information is represented
only by positive and negative voltages But if control signals are encoded
using a meaningful control characters from a system such as ASCII it can be transmitted over data lines
bull X21 eliminates most of the control circuits of the EIA standards and
instead directs its traffic over the data circuits To make this consolidationof functionality possible both the DTE and the DCE must have added
circuit logic that enables them to transform the control codes into bit
streams that can be sent over the data line Both also need additional logicto discriminate between control information and data upon receipt
bull Design of X21 allows not only to use fewer pins but also to be used in
digital telecommunications where control information is sent from deviceto device over a network rather than just between a DTE and a DCE
bull X21 is useful both as an interface to connect digital computers to analogdevices such as modems and as a connector between digital computers and
digital interfaces such as ISDN and X25
Byte Timing
bull Another advantage offered by X21 is that of timing lines to control bytesynchronization in addition to the bit synchronization provided by the EIA
standards By adding a byte timing pulse improves the overall
synchronization of transmissions
Control and indication
bull Pins 3 and 5 of the DB-15 connector are used for the initial handshake or
agreement to begin transmitting Pin 3 is the equivalent of request to send
Pin 5 is the equivalent of clear to send
MODEMbull Modem stands for modulatordemodulator
bull A modulator converts a digital to an analog signalbull A demodulator converts an analog signal to a digital signal
bull The series of 1s and 0s are transformed through the mechanism of ASK
FSK PSK and QAM
Transmission Rate
Bandwidth
bull Every line has upper limit and a lower limit on the frequencies of the
signals it carry this limited range is called the bandwidth
It handles connection establishment and termination data transfer
and packet creation protocols Two types of PLP packets information and control
Up to 4096 channels may be multiplexed at the PLP level Specifies protocols to handle resizing of messages
FRAME RELAY LAYERSbull A technology that operates only at the physical and datalink layers No protocol is
specified for the physical layer the choice is up to the user
bull Eliminates the extensive error checking necessary in X25 protocol
bull It uses simplified version of HDLC protocol in the datalink layerbull It uses routing and switching functions of the datalink layers Frames not packets
are switched
bull It uses PVCs (permanent virtual circuits) Identified through a DLCI (dalta linkconnection identifier)
bull A switch in frame relay performs error checking and routing Error correction is
left to the other protocols at the higher layers
bull Flow control is handled through setting the BECN (backwards explicit congestionnotification) and FECN (forward explicit congestion notification) in the address
field of the frame
bull
ASYNCHRONOUS TRANSFER MODE (ATM)
bull Is the cell relay protocol designed by the ATM forum and adopted by theITU-T
bull In ATM some software functions have moved to hardware this can
increase the data rate
Terms
Cell is the data packet is called a and is composed of 53 bytes (5 bytes of header and 48 bytes of payload) Because each cell is the same size and all are relatively small delay
and other problems associated with multiplexing different sized packets are avoided
A cell network is based on permanent virtual circuit (PVC) routing
bull Virtual Path Identifier (VPI) specifies the path a cell should take
1 Virtual path (VP) switching ndash channels within each VP remain with the VP
2 Virtual path and channel (VPC) switching ndash a channel from one VP may pass into
another VP
IXSDHSONET
Synchronous Optical Network (SONET)
Developed by ANSI
Synchronous Digital Hierarchy (SDH)
Developed by ITU-T
SONETSDH
The two are nearly identical ANSI and ITU-T defined standards that arefundamentally similar and ultimately compatible
Is a synchronous network a single clock is used to handle the timing of
transmissions and equipment across the entire network
SONET
It defines the hierarchy of signals called synchronous transport signals (STS)
Optical carrier (OC) levels are the implementation of STS
SONETSDH Rates
STS OC Rate (Mbps) STM
STS-1 OC-1 5184
STS-3 OC-3 15552 STM-1
STS-9 OC-9 46656 STM-3
STS-12 OC-12 62208 STM-4
STS-18 OC-18 93312 STM-6
STS-24 OC-24 124416 STM-8
STS-36 OC-36 186623 STM-12
STS-48 OC-48 248832 STM-16
STS-96 OC-96 497664 STM-32
STS-192 OC-192 995328 STM-64
STM-synchronous transport module
SONET Four Layers
1 Photonic layer is the lowest and performs physical layer activities
A frame at the photonic layer for STS-1 consists of 6480 bits (8000 framessec)
2-4 Section Line and Path layers correspond to the OSI modelrsquos datalink layer Eachof these layers is responsible for signal transfer across a specific portion of the
1 STS multiplexer combines several optical signals to make an STS signal2 Regenerator removes noise from optical signal
3 Adddrop multiplexer adds STS signals from different paths and removes STS signal
from a path
XTCPIP
Transmission Control ProtocolInternetworking Protocol (TCPIP)
Is a set of rules and procedures that governs the exchange of messages in an
internetwork Originally developed as a protocol for networks that wanted to be connected to
ARPANET a US Department of Defense project now known as Internet
Is a five-layer protocol suite whose bottom four layers match the OSI model fairly
closely The highest level the application layer corresponds to OSIrsquos top threelayers
Internet Protocol (IP) Is defined at the network layer
Unreliable and connectionless Is basically the set of rules for one network communicating with any other To be part of internet organization needs an internet network number unique
number to be included in any packet sent out of the network onto the internet
IP packet is known as datagram consists of a variable header and a variable data
field
IP Address
Uniquely defines the connection of a host to its network The host with more than
one IP address is multi-homed host
IP Addressing
32 bit binary number usually represented as 4 decimal values Equivalent to 4 octets ( 8 bits each decimal value ) Dotted decimal notation Consists of 2 parts the network and the node
Network ndash identifier of particular network on the internet
Host ndash identifier of a particular device which can be a server or a
bull A large proportion of the circuits in the EIA interfaces are used forcontrol since these are necessary to implement control functions as
separate signals With a separate line control information is represented
only by positive and negative voltages But if control signals are encoded
using a meaningful control characters from a system such as ASCII it can be transmitted over data lines
bull X21 eliminates most of the control circuits of the EIA standards and
instead directs its traffic over the data circuits To make this consolidationof functionality possible both the DTE and the DCE must have added
circuit logic that enables them to transform the control codes into bit
streams that can be sent over the data line Both also need additional logicto discriminate between control information and data upon receipt
bull Design of X21 allows not only to use fewer pins but also to be used in
digital telecommunications where control information is sent from deviceto device over a network rather than just between a DTE and a DCE
bull X21 is useful both as an interface to connect digital computers to analogdevices such as modems and as a connector between digital computers and
digital interfaces such as ISDN and X25
Byte Timing
bull Another advantage offered by X21 is that of timing lines to control bytesynchronization in addition to the bit synchronization provided by the EIA
standards By adding a byte timing pulse improves the overall
synchronization of transmissions
Control and indication
bull Pins 3 and 5 of the DB-15 connector are used for the initial handshake or
agreement to begin transmitting Pin 3 is the equivalent of request to send
Pin 5 is the equivalent of clear to send
MODEMbull Modem stands for modulatordemodulator
bull A modulator converts a digital to an analog signalbull A demodulator converts an analog signal to a digital signal
bull The series of 1s and 0s are transformed through the mechanism of ASK
FSK PSK and QAM
Transmission Rate
Bandwidth
bull Every line has upper limit and a lower limit on the frequencies of the
signals it carry this limited range is called the bandwidth
It handles connection establishment and termination data transfer
and packet creation protocols Two types of PLP packets information and control
Up to 4096 channels may be multiplexed at the PLP level Specifies protocols to handle resizing of messages
FRAME RELAY LAYERSbull A technology that operates only at the physical and datalink layers No protocol is
specified for the physical layer the choice is up to the user
bull Eliminates the extensive error checking necessary in X25 protocol
bull It uses simplified version of HDLC protocol in the datalink layerbull It uses routing and switching functions of the datalink layers Frames not packets
are switched
bull It uses PVCs (permanent virtual circuits) Identified through a DLCI (dalta linkconnection identifier)
bull A switch in frame relay performs error checking and routing Error correction is
left to the other protocols at the higher layers
bull Flow control is handled through setting the BECN (backwards explicit congestionnotification) and FECN (forward explicit congestion notification) in the address
field of the frame
bull
ASYNCHRONOUS TRANSFER MODE (ATM)
bull Is the cell relay protocol designed by the ATM forum and adopted by theITU-T
bull In ATM some software functions have moved to hardware this can
increase the data rate
Terms
Cell is the data packet is called a and is composed of 53 bytes (5 bytes of header and 48 bytes of payload) Because each cell is the same size and all are relatively small delay
and other problems associated with multiplexing different sized packets are avoided
A cell network is based on permanent virtual circuit (PVC) routing
bull Virtual Path Identifier (VPI) specifies the path a cell should take
1 Virtual path (VP) switching ndash channels within each VP remain with the VP
2 Virtual path and channel (VPC) switching ndash a channel from one VP may pass into
another VP
IXSDHSONET
Synchronous Optical Network (SONET)
Developed by ANSI
Synchronous Digital Hierarchy (SDH)
Developed by ITU-T
SONETSDH
The two are nearly identical ANSI and ITU-T defined standards that arefundamentally similar and ultimately compatible
Is a synchronous network a single clock is used to handle the timing of
transmissions and equipment across the entire network
SONET
It defines the hierarchy of signals called synchronous transport signals (STS)
Optical carrier (OC) levels are the implementation of STS
SONETSDH Rates
STS OC Rate (Mbps) STM
STS-1 OC-1 5184
STS-3 OC-3 15552 STM-1
STS-9 OC-9 46656 STM-3
STS-12 OC-12 62208 STM-4
STS-18 OC-18 93312 STM-6
STS-24 OC-24 124416 STM-8
STS-36 OC-36 186623 STM-12
STS-48 OC-48 248832 STM-16
STS-96 OC-96 497664 STM-32
STS-192 OC-192 995328 STM-64
STM-synchronous transport module
SONET Four Layers
1 Photonic layer is the lowest and performs physical layer activities
A frame at the photonic layer for STS-1 consists of 6480 bits (8000 framessec)
2-4 Section Line and Path layers correspond to the OSI modelrsquos datalink layer Eachof these layers is responsible for signal transfer across a specific portion of the
1 STS multiplexer combines several optical signals to make an STS signal2 Regenerator removes noise from optical signal
3 Adddrop multiplexer adds STS signals from different paths and removes STS signal
from a path
XTCPIP
Transmission Control ProtocolInternetworking Protocol (TCPIP)
Is a set of rules and procedures that governs the exchange of messages in an
internetwork Originally developed as a protocol for networks that wanted to be connected to
ARPANET a US Department of Defense project now known as Internet
Is a five-layer protocol suite whose bottom four layers match the OSI model fairly
closely The highest level the application layer corresponds to OSIrsquos top threelayers
Internet Protocol (IP) Is defined at the network layer
Unreliable and connectionless Is basically the set of rules for one network communicating with any other To be part of internet organization needs an internet network number unique
number to be included in any packet sent out of the network onto the internet
IP packet is known as datagram consists of a variable header and a variable data
field
IP Address
Uniquely defines the connection of a host to its network The host with more than
one IP address is multi-homed host
IP Addressing
32 bit binary number usually represented as 4 decimal values Equivalent to 4 octets ( 8 bits each decimal value ) Dotted decimal notation Consists of 2 parts the network and the node
Network ndash identifier of particular network on the internet
Host ndash identifier of a particular device which can be a server or a
It handles connection establishment and termination data transfer
and packet creation protocols Two types of PLP packets information and control
Up to 4096 channels may be multiplexed at the PLP level Specifies protocols to handle resizing of messages
FRAME RELAY LAYERSbull A technology that operates only at the physical and datalink layers No protocol is
specified for the physical layer the choice is up to the user
bull Eliminates the extensive error checking necessary in X25 protocol
bull It uses simplified version of HDLC protocol in the datalink layerbull It uses routing and switching functions of the datalink layers Frames not packets
are switched
bull It uses PVCs (permanent virtual circuits) Identified through a DLCI (dalta linkconnection identifier)
bull A switch in frame relay performs error checking and routing Error correction is
left to the other protocols at the higher layers
bull Flow control is handled through setting the BECN (backwards explicit congestionnotification) and FECN (forward explicit congestion notification) in the address
field of the frame
bull
ASYNCHRONOUS TRANSFER MODE (ATM)
bull Is the cell relay protocol designed by the ATM forum and adopted by theITU-T
bull In ATM some software functions have moved to hardware this can
increase the data rate
Terms
Cell is the data packet is called a and is composed of 53 bytes (5 bytes of header and 48 bytes of payload) Because each cell is the same size and all are relatively small delay
and other problems associated with multiplexing different sized packets are avoided
A cell network is based on permanent virtual circuit (PVC) routing
bull Virtual Path Identifier (VPI) specifies the path a cell should take
1 Virtual path (VP) switching ndash channels within each VP remain with the VP
2 Virtual path and channel (VPC) switching ndash a channel from one VP may pass into
another VP
IXSDHSONET
Synchronous Optical Network (SONET)
Developed by ANSI
Synchronous Digital Hierarchy (SDH)
Developed by ITU-T
SONETSDH
The two are nearly identical ANSI and ITU-T defined standards that arefundamentally similar and ultimately compatible
Is a synchronous network a single clock is used to handle the timing of
transmissions and equipment across the entire network
SONET
It defines the hierarchy of signals called synchronous transport signals (STS)
Optical carrier (OC) levels are the implementation of STS
SONETSDH Rates
STS OC Rate (Mbps) STM
STS-1 OC-1 5184
STS-3 OC-3 15552 STM-1
STS-9 OC-9 46656 STM-3
STS-12 OC-12 62208 STM-4
STS-18 OC-18 93312 STM-6
STS-24 OC-24 124416 STM-8
STS-36 OC-36 186623 STM-12
STS-48 OC-48 248832 STM-16
STS-96 OC-96 497664 STM-32
STS-192 OC-192 995328 STM-64
STM-synchronous transport module
SONET Four Layers
1 Photonic layer is the lowest and performs physical layer activities
A frame at the photonic layer for STS-1 consists of 6480 bits (8000 framessec)
2-4 Section Line and Path layers correspond to the OSI modelrsquos datalink layer Eachof these layers is responsible for signal transfer across a specific portion of the
1 STS multiplexer combines several optical signals to make an STS signal2 Regenerator removes noise from optical signal
3 Adddrop multiplexer adds STS signals from different paths and removes STS signal
from a path
XTCPIP
Transmission Control ProtocolInternetworking Protocol (TCPIP)
Is a set of rules and procedures that governs the exchange of messages in an
internetwork Originally developed as a protocol for networks that wanted to be connected to
ARPANET a US Department of Defense project now known as Internet
Is a five-layer protocol suite whose bottom four layers match the OSI model fairly
closely The highest level the application layer corresponds to OSIrsquos top threelayers
Internet Protocol (IP) Is defined at the network layer
Unreliable and connectionless Is basically the set of rules for one network communicating with any other To be part of internet organization needs an internet network number unique
number to be included in any packet sent out of the network onto the internet
IP packet is known as datagram consists of a variable header and a variable data
field
IP Address
Uniquely defines the connection of a host to its network The host with more than
one IP address is multi-homed host
IP Addressing
32 bit binary number usually represented as 4 decimal values Equivalent to 4 octets ( 8 bits each decimal value ) Dotted decimal notation Consists of 2 parts the network and the node
Network ndash identifier of particular network on the internet
Host ndash identifier of a particular device which can be a server or a
It handles connection establishment and termination data transfer
and packet creation protocols Two types of PLP packets information and control
Up to 4096 channels may be multiplexed at the PLP level Specifies protocols to handle resizing of messages
FRAME RELAY LAYERSbull A technology that operates only at the physical and datalink layers No protocol is
specified for the physical layer the choice is up to the user
bull Eliminates the extensive error checking necessary in X25 protocol
bull It uses simplified version of HDLC protocol in the datalink layerbull It uses routing and switching functions of the datalink layers Frames not packets
are switched
bull It uses PVCs (permanent virtual circuits) Identified through a DLCI (dalta linkconnection identifier)
bull A switch in frame relay performs error checking and routing Error correction is
left to the other protocols at the higher layers
bull Flow control is handled through setting the BECN (backwards explicit congestionnotification) and FECN (forward explicit congestion notification) in the address
field of the frame
bull
ASYNCHRONOUS TRANSFER MODE (ATM)
bull Is the cell relay protocol designed by the ATM forum and adopted by theITU-T
bull In ATM some software functions have moved to hardware this can
increase the data rate
Terms
Cell is the data packet is called a and is composed of 53 bytes (5 bytes of header and 48 bytes of payload) Because each cell is the same size and all are relatively small delay
and other problems associated with multiplexing different sized packets are avoided
A cell network is based on permanent virtual circuit (PVC) routing
bull Virtual Path Identifier (VPI) specifies the path a cell should take
1 Virtual path (VP) switching ndash channels within each VP remain with the VP
2 Virtual path and channel (VPC) switching ndash a channel from one VP may pass into
another VP
IXSDHSONET
Synchronous Optical Network (SONET)
Developed by ANSI
Synchronous Digital Hierarchy (SDH)
Developed by ITU-T
SONETSDH
The two are nearly identical ANSI and ITU-T defined standards that arefundamentally similar and ultimately compatible
Is a synchronous network a single clock is used to handle the timing of
transmissions and equipment across the entire network
SONET
It defines the hierarchy of signals called synchronous transport signals (STS)
Optical carrier (OC) levels are the implementation of STS
SONETSDH Rates
STS OC Rate (Mbps) STM
STS-1 OC-1 5184
STS-3 OC-3 15552 STM-1
STS-9 OC-9 46656 STM-3
STS-12 OC-12 62208 STM-4
STS-18 OC-18 93312 STM-6
STS-24 OC-24 124416 STM-8
STS-36 OC-36 186623 STM-12
STS-48 OC-48 248832 STM-16
STS-96 OC-96 497664 STM-32
STS-192 OC-192 995328 STM-64
STM-synchronous transport module
SONET Four Layers
1 Photonic layer is the lowest and performs physical layer activities
A frame at the photonic layer for STS-1 consists of 6480 bits (8000 framessec)
2-4 Section Line and Path layers correspond to the OSI modelrsquos datalink layer Eachof these layers is responsible for signal transfer across a specific portion of the
1 STS multiplexer combines several optical signals to make an STS signal2 Regenerator removes noise from optical signal
3 Adddrop multiplexer adds STS signals from different paths and removes STS signal
from a path
XTCPIP
Transmission Control ProtocolInternetworking Protocol (TCPIP)
Is a set of rules and procedures that governs the exchange of messages in an
internetwork Originally developed as a protocol for networks that wanted to be connected to
ARPANET a US Department of Defense project now known as Internet
Is a five-layer protocol suite whose bottom four layers match the OSI model fairly
closely The highest level the application layer corresponds to OSIrsquos top threelayers
Internet Protocol (IP) Is defined at the network layer
Unreliable and connectionless Is basically the set of rules for one network communicating with any other To be part of internet organization needs an internet network number unique
number to be included in any packet sent out of the network onto the internet
IP packet is known as datagram consists of a variable header and a variable data
field
IP Address
Uniquely defines the connection of a host to its network The host with more than
one IP address is multi-homed host
IP Addressing
32 bit binary number usually represented as 4 decimal values Equivalent to 4 octets ( 8 bits each decimal value ) Dotted decimal notation Consists of 2 parts the network and the node
Network ndash identifier of particular network on the internet
Host ndash identifier of a particular device which can be a server or a
It handles connection establishment and termination data transfer
and packet creation protocols Two types of PLP packets information and control
Up to 4096 channels may be multiplexed at the PLP level Specifies protocols to handle resizing of messages
FRAME RELAY LAYERSbull A technology that operates only at the physical and datalink layers No protocol is
specified for the physical layer the choice is up to the user
bull Eliminates the extensive error checking necessary in X25 protocol
bull It uses simplified version of HDLC protocol in the datalink layerbull It uses routing and switching functions of the datalink layers Frames not packets
are switched
bull It uses PVCs (permanent virtual circuits) Identified through a DLCI (dalta linkconnection identifier)
bull A switch in frame relay performs error checking and routing Error correction is
left to the other protocols at the higher layers
bull Flow control is handled through setting the BECN (backwards explicit congestionnotification) and FECN (forward explicit congestion notification) in the address
field of the frame
bull
ASYNCHRONOUS TRANSFER MODE (ATM)
bull Is the cell relay protocol designed by the ATM forum and adopted by theITU-T
bull In ATM some software functions have moved to hardware this can
increase the data rate
Terms
Cell is the data packet is called a and is composed of 53 bytes (5 bytes of header and 48 bytes of payload) Because each cell is the same size and all are relatively small delay
and other problems associated with multiplexing different sized packets are avoided
A cell network is based on permanent virtual circuit (PVC) routing
bull Virtual Path Identifier (VPI) specifies the path a cell should take
1 Virtual path (VP) switching ndash channels within each VP remain with the VP
2 Virtual path and channel (VPC) switching ndash a channel from one VP may pass into
another VP
IXSDHSONET
Synchronous Optical Network (SONET)
Developed by ANSI
Synchronous Digital Hierarchy (SDH)
Developed by ITU-T
SONETSDH
The two are nearly identical ANSI and ITU-T defined standards that arefundamentally similar and ultimately compatible
Is a synchronous network a single clock is used to handle the timing of
transmissions and equipment across the entire network
SONET
It defines the hierarchy of signals called synchronous transport signals (STS)
Optical carrier (OC) levels are the implementation of STS
SONETSDH Rates
STS OC Rate (Mbps) STM
STS-1 OC-1 5184
STS-3 OC-3 15552 STM-1
STS-9 OC-9 46656 STM-3
STS-12 OC-12 62208 STM-4
STS-18 OC-18 93312 STM-6
STS-24 OC-24 124416 STM-8
STS-36 OC-36 186623 STM-12
STS-48 OC-48 248832 STM-16
STS-96 OC-96 497664 STM-32
STS-192 OC-192 995328 STM-64
STM-synchronous transport module
SONET Four Layers
1 Photonic layer is the lowest and performs physical layer activities
A frame at the photonic layer for STS-1 consists of 6480 bits (8000 framessec)
2-4 Section Line and Path layers correspond to the OSI modelrsquos datalink layer Eachof these layers is responsible for signal transfer across a specific portion of the
1 STS multiplexer combines several optical signals to make an STS signal2 Regenerator removes noise from optical signal
3 Adddrop multiplexer adds STS signals from different paths and removes STS signal
from a path
XTCPIP
Transmission Control ProtocolInternetworking Protocol (TCPIP)
Is a set of rules and procedures that governs the exchange of messages in an
internetwork Originally developed as a protocol for networks that wanted to be connected to
ARPANET a US Department of Defense project now known as Internet
Is a five-layer protocol suite whose bottom four layers match the OSI model fairly
closely The highest level the application layer corresponds to OSIrsquos top threelayers
Internet Protocol (IP) Is defined at the network layer
Unreliable and connectionless Is basically the set of rules for one network communicating with any other To be part of internet organization needs an internet network number unique
number to be included in any packet sent out of the network onto the internet
IP packet is known as datagram consists of a variable header and a variable data
field
IP Address
Uniquely defines the connection of a host to its network The host with more than
one IP address is multi-homed host
IP Addressing
32 bit binary number usually represented as 4 decimal values Equivalent to 4 octets ( 8 bits each decimal value ) Dotted decimal notation Consists of 2 parts the network and the node
Network ndash identifier of particular network on the internet
Host ndash identifier of a particular device which can be a server or a
It handles connection establishment and termination data transfer
and packet creation protocols Two types of PLP packets information and control
Up to 4096 channels may be multiplexed at the PLP level Specifies protocols to handle resizing of messages
FRAME RELAY LAYERSbull A technology that operates only at the physical and datalink layers No protocol is
specified for the physical layer the choice is up to the user
bull Eliminates the extensive error checking necessary in X25 protocol
bull It uses simplified version of HDLC protocol in the datalink layerbull It uses routing and switching functions of the datalink layers Frames not packets
are switched
bull It uses PVCs (permanent virtual circuits) Identified through a DLCI (dalta linkconnection identifier)
bull A switch in frame relay performs error checking and routing Error correction is
left to the other protocols at the higher layers
bull Flow control is handled through setting the BECN (backwards explicit congestionnotification) and FECN (forward explicit congestion notification) in the address
field of the frame
bull
ASYNCHRONOUS TRANSFER MODE (ATM)
bull Is the cell relay protocol designed by the ATM forum and adopted by theITU-T
bull In ATM some software functions have moved to hardware this can
increase the data rate
Terms
Cell is the data packet is called a and is composed of 53 bytes (5 bytes of header and 48 bytes of payload) Because each cell is the same size and all are relatively small delay
and other problems associated with multiplexing different sized packets are avoided
A cell network is based on permanent virtual circuit (PVC) routing
bull Virtual Path Identifier (VPI) specifies the path a cell should take
1 Virtual path (VP) switching ndash channels within each VP remain with the VP
2 Virtual path and channel (VPC) switching ndash a channel from one VP may pass into
another VP
IXSDHSONET
Synchronous Optical Network (SONET)
Developed by ANSI
Synchronous Digital Hierarchy (SDH)
Developed by ITU-T
SONETSDH
The two are nearly identical ANSI and ITU-T defined standards that arefundamentally similar and ultimately compatible
Is a synchronous network a single clock is used to handle the timing of
transmissions and equipment across the entire network
SONET
It defines the hierarchy of signals called synchronous transport signals (STS)
Optical carrier (OC) levels are the implementation of STS
SONETSDH Rates
STS OC Rate (Mbps) STM
STS-1 OC-1 5184
STS-3 OC-3 15552 STM-1
STS-9 OC-9 46656 STM-3
STS-12 OC-12 62208 STM-4
STS-18 OC-18 93312 STM-6
STS-24 OC-24 124416 STM-8
STS-36 OC-36 186623 STM-12
STS-48 OC-48 248832 STM-16
STS-96 OC-96 497664 STM-32
STS-192 OC-192 995328 STM-64
STM-synchronous transport module
SONET Four Layers
1 Photonic layer is the lowest and performs physical layer activities
A frame at the photonic layer for STS-1 consists of 6480 bits (8000 framessec)
2-4 Section Line and Path layers correspond to the OSI modelrsquos datalink layer Eachof these layers is responsible for signal transfer across a specific portion of the
1 STS multiplexer combines several optical signals to make an STS signal2 Regenerator removes noise from optical signal
3 Adddrop multiplexer adds STS signals from different paths and removes STS signal
from a path
XTCPIP
Transmission Control ProtocolInternetworking Protocol (TCPIP)
Is a set of rules and procedures that governs the exchange of messages in an
internetwork Originally developed as a protocol for networks that wanted to be connected to
ARPANET a US Department of Defense project now known as Internet
Is a five-layer protocol suite whose bottom four layers match the OSI model fairly
closely The highest level the application layer corresponds to OSIrsquos top threelayers
Internet Protocol (IP) Is defined at the network layer
Unreliable and connectionless Is basically the set of rules for one network communicating with any other To be part of internet organization needs an internet network number unique
number to be included in any packet sent out of the network onto the internet
IP packet is known as datagram consists of a variable header and a variable data
field
IP Address
Uniquely defines the connection of a host to its network The host with more than
one IP address is multi-homed host
IP Addressing
32 bit binary number usually represented as 4 decimal values Equivalent to 4 octets ( 8 bits each decimal value ) Dotted decimal notation Consists of 2 parts the network and the node
Network ndash identifier of particular network on the internet
Host ndash identifier of a particular device which can be a server or a
1 Virtual path (VP) switching ndash channels within each VP remain with the VP
2 Virtual path and channel (VPC) switching ndash a channel from one VP may pass into
another VP
IXSDHSONET
Synchronous Optical Network (SONET)
Developed by ANSI
Synchronous Digital Hierarchy (SDH)
Developed by ITU-T
SONETSDH
The two are nearly identical ANSI and ITU-T defined standards that arefundamentally similar and ultimately compatible
Is a synchronous network a single clock is used to handle the timing of
transmissions and equipment across the entire network
SONET
It defines the hierarchy of signals called synchronous transport signals (STS)
Optical carrier (OC) levels are the implementation of STS
SONETSDH Rates
STS OC Rate (Mbps) STM
STS-1 OC-1 5184
STS-3 OC-3 15552 STM-1
STS-9 OC-9 46656 STM-3
STS-12 OC-12 62208 STM-4
STS-18 OC-18 93312 STM-6
STS-24 OC-24 124416 STM-8
STS-36 OC-36 186623 STM-12
STS-48 OC-48 248832 STM-16
STS-96 OC-96 497664 STM-32
STS-192 OC-192 995328 STM-64
STM-synchronous transport module
SONET Four Layers
1 Photonic layer is the lowest and performs physical layer activities
A frame at the photonic layer for STS-1 consists of 6480 bits (8000 framessec)
2-4 Section Line and Path layers correspond to the OSI modelrsquos datalink layer Eachof these layers is responsible for signal transfer across a specific portion of the
1 STS multiplexer combines several optical signals to make an STS signal2 Regenerator removes noise from optical signal
3 Adddrop multiplexer adds STS signals from different paths and removes STS signal
from a path
XTCPIP
Transmission Control ProtocolInternetworking Protocol (TCPIP)
Is a set of rules and procedures that governs the exchange of messages in an
internetwork Originally developed as a protocol for networks that wanted to be connected to
ARPANET a US Department of Defense project now known as Internet
Is a five-layer protocol suite whose bottom four layers match the OSI model fairly
closely The highest level the application layer corresponds to OSIrsquos top threelayers
Internet Protocol (IP) Is defined at the network layer
Unreliable and connectionless Is basically the set of rules for one network communicating with any other To be part of internet organization needs an internet network number unique
number to be included in any packet sent out of the network onto the internet
IP packet is known as datagram consists of a variable header and a variable data
field
IP Address
Uniquely defines the connection of a host to its network The host with more than
one IP address is multi-homed host
IP Addressing
32 bit binary number usually represented as 4 decimal values Equivalent to 4 octets ( 8 bits each decimal value ) Dotted decimal notation Consists of 2 parts the network and the node
Network ndash identifier of particular network on the internet
Host ndash identifier of a particular device which can be a server or a
1 Virtual path (VP) switching ndash channels within each VP remain with the VP
2 Virtual path and channel (VPC) switching ndash a channel from one VP may pass into
another VP
IXSDHSONET
Synchronous Optical Network (SONET)
Developed by ANSI
Synchronous Digital Hierarchy (SDH)
Developed by ITU-T
SONETSDH
The two are nearly identical ANSI and ITU-T defined standards that arefundamentally similar and ultimately compatible
Is a synchronous network a single clock is used to handle the timing of
transmissions and equipment across the entire network
SONET
It defines the hierarchy of signals called synchronous transport signals (STS)
Optical carrier (OC) levels are the implementation of STS
SONETSDH Rates
STS OC Rate (Mbps) STM
STS-1 OC-1 5184
STS-3 OC-3 15552 STM-1
STS-9 OC-9 46656 STM-3
STS-12 OC-12 62208 STM-4
STS-18 OC-18 93312 STM-6
STS-24 OC-24 124416 STM-8
STS-36 OC-36 186623 STM-12
STS-48 OC-48 248832 STM-16
STS-96 OC-96 497664 STM-32
STS-192 OC-192 995328 STM-64
STM-synchronous transport module
SONET Four Layers
1 Photonic layer is the lowest and performs physical layer activities
A frame at the photonic layer for STS-1 consists of 6480 bits (8000 framessec)
2-4 Section Line and Path layers correspond to the OSI modelrsquos datalink layer Eachof these layers is responsible for signal transfer across a specific portion of the
1 STS multiplexer combines several optical signals to make an STS signal2 Regenerator removes noise from optical signal
3 Adddrop multiplexer adds STS signals from different paths and removes STS signal
from a path
XTCPIP
Transmission Control ProtocolInternetworking Protocol (TCPIP)
Is a set of rules and procedures that governs the exchange of messages in an
internetwork Originally developed as a protocol for networks that wanted to be connected to
ARPANET a US Department of Defense project now known as Internet
Is a five-layer protocol suite whose bottom four layers match the OSI model fairly
closely The highest level the application layer corresponds to OSIrsquos top threelayers
Internet Protocol (IP) Is defined at the network layer
Unreliable and connectionless Is basically the set of rules for one network communicating with any other To be part of internet organization needs an internet network number unique
number to be included in any packet sent out of the network onto the internet
IP packet is known as datagram consists of a variable header and a variable data
field
IP Address
Uniquely defines the connection of a host to its network The host with more than
one IP address is multi-homed host
IP Addressing
32 bit binary number usually represented as 4 decimal values Equivalent to 4 octets ( 8 bits each decimal value ) Dotted decimal notation Consists of 2 parts the network and the node
Network ndash identifier of particular network on the internet
Host ndash identifier of a particular device which can be a server or a
1 STS multiplexer combines several optical signals to make an STS signal2 Regenerator removes noise from optical signal
3 Adddrop multiplexer adds STS signals from different paths and removes STS signal
from a path
XTCPIP
Transmission Control ProtocolInternetworking Protocol (TCPIP)
Is a set of rules and procedures that governs the exchange of messages in an
internetwork Originally developed as a protocol for networks that wanted to be connected to
ARPANET a US Department of Defense project now known as Internet
Is a five-layer protocol suite whose bottom four layers match the OSI model fairly
closely The highest level the application layer corresponds to OSIrsquos top threelayers
Internet Protocol (IP) Is defined at the network layer
Unreliable and connectionless Is basically the set of rules for one network communicating with any other To be part of internet organization needs an internet network number unique
number to be included in any packet sent out of the network onto the internet
IP packet is known as datagram consists of a variable header and a variable data
field
IP Address
Uniquely defines the connection of a host to its network The host with more than
one IP address is multi-homed host
IP Addressing
32 bit binary number usually represented as 4 decimal values Equivalent to 4 octets ( 8 bits each decimal value ) Dotted decimal notation Consists of 2 parts the network and the node
Network ndash identifier of particular network on the internet
Host ndash identifier of a particular device which can be a server or a