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Network HardwareNetwork Hardware
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Types of Network TopologiesTypes of Network Topologies
BusBus
StarStar
RingRing
MeshMesh
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Bus TopologyBus Topology
1. A Bus Topology Network uses a long cable , called the BACKBONE
2. PC’s are connected to the BACKBONE with Small Cables ( called
DROP Cables ) using T-Connectors & BNC connectors .
3. To avoid Signal- Bouncing , the backbone is “Terminated” both ends
4. BUS is a Passive Topology as there are no Active electronics to
amplify the signal in this type of Network
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Bus TopologyBus Topology
1. Ethernet 10Base2 is a common BUS topology Network ( Thinnet )
Ethernet 10Base5 is known as Thicknet .
2. Cables used are Thick & Thin Co-Axial cable
3. Segment length is 185 metres for Thin Co-axial Cable ( RG-58 )&
500 metres for Thick Co-Axial Cable ( RG-11 )
4. Bandwidth is 10 MBPS
5. To increase the segment length REPEATERS are used .
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Advantages of BUS TopologyAdvantages of BUS Topology
1. The bus is simple, reliable in very small networks, easy to use & install , and easy to understand.
2. The bus requires the least amount of cable to connect the computers together and is therefore less expensive than other cabling arrangements.
3. It is easy to extend a bus. Two cables can be joined into one longer cable with a BNC barrel connector, making a longer cable and allowing more computers to join the network.
4. A repeater can also be used to extend a bus; a repeater boosts the signal and allows it to travel a longer distance.
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Disadvantages of BUS TopologyDisadvantages of BUS Topology
1. If there is any breakage in the BUS the whole network is down .
2. It is difficult to troubleshoot a bus. A cable break or malfunctioning computer anywhere between two computers can cause them not to be able to communicate with each other. A cable break or loose connector will also cause reflections and bring down the whole network, causing all network activity to stop.
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Star TopologyStar Topology
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In a star topology, all the cables run from the computers to a central location, where they are all connected by a device called a hub.
Stars are used in concentrated networks, where the endpoints are directly reachable from a central location; when network expansion is expected; and when the greater reliability of a star topology is needed.
Star TopologyStar Topology
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How a Star Network WorksHow a Star Network Works
Each computer on a star network communicates with a central hub that resends the message either to all the computers (in a broadcast star network) or only to the destination computer (in a switched star network).
An active hub regenerates the electrical signal and sends it to all the computers connected to it. This type of hub is often called a multiport repeater. Active hubs and switches require electrical power to run.
Ethernet 10baseT is a popular network based on the
star topology.
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Advantages of STAR TopologyAdvantages of STAR Topology
It is easy to modify and add new computers to a star network without disturbing the rest of the network.
Provides centralized monitoring and management of the network.
Single computer failures do not necessarily bring down the whole star Network.
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Disadvantages of STAR TopologyDisadvantages of STAR Topology
If the central hub fails, the whole network fails to operate.
It costs more to cable a star network because all network cables must be pulled to one central point, requiring more cable than other networking topologies.
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RING TopologyRING Topology
In a ring topology, each computer is connected to the next computer, with the last one connected to the first.
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How a Ring Network WorksHow a Ring Network Works
1. No terminators read.
2. Signals travels around the loop in one direction and passes through each computer .
3. It is an Active topology , because , each PC acts as a repeater to boost the signal to the next PC.
4. Because the signal passes through each PC , the failure of one PC can impact the entire network .
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5. One method of Transmitting data around the Ring is called Token passing.
6. The sending PC modifies the Token by putting electronic address on the data and sends it around the Ring .
7. The data passes through each PC until it finds the actual destination address PC that is encoded with the data .
8.The receiving PC returns a message to the sending PC indicating the receipt of data . After the acknowledgement is recd by the sending PC , it creates a new token and releases it on the network .
FDDI is a fast fiber-optic network based on the ring topology.
How a Ring Network Works (Cont.)How a Ring Network Works (Cont.)
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Advantages of RING TopologyAdvantages of RING Topology
Because every computer is given equal access to the token, no one computer can monopolize the network.
The fair sharing of the network allows the network to degrade gracefully (continue to function in a useful, if slower, manner rather than fail once capacity is exceeded) as more users are added.
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Failure of one computer on the ring can affect the whole network.
It is difficult to troubleshoot a ring network.
Adding or removing computers disrupts the network.
Advantages of RING TopologyAdvantages of RING Topology
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Mesh TopologyMesh Topology
4+3+2+1 = 10 concatenations
For 5 devices -------a Advantage :
1. Extremely fault tolerant
Disadvantage:
1. Very Complex to install & troubleshoot
2. High Cabling cost.
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Considerations When Choosing aTopology:
Money. A linear bus network may be the least expensive way to
install a network; you do not have to purchase concentrators.
Length of cable needed. The linear bus network uses shorter
lengths of cable.
Future growth. With a star topology, expanding a network is easily
done by adding another concentrator.
Cable type. The most common cable in schools is unshielded
twisted pair, which is most often used with star topologies.
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Summary Chart
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Network Media
Types of Network MediaTypes of Network Media
1. Cable Media
2. Wireless Media
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Cable Media:
1. Coaxial
2. Twisted Pair
3. Fiber-optic
Wireless Media :
1. Radio frequency
2. Microwave
3. Infrared
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CO-AXIALCO-AXIAL
Co-axial Cable (Commonly called “Coax”) is made of Two conductors that common axis , hence the name (“ co,” “axis” ). Typically the center of the cable is relatively stiff solid copper wire or stranded wire incased in insulating plastic foam . The foam is surrounded by the second conductor , a wire meshed tube ( Some include conductive foil wrap ), which serves as a shield from EMI. A tuff, insulating plastic tube forms the cover of the cable .
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1.Thin Ethernet
2.Thick Ethernet
3. Arc net
Types of Coaxial Cable:
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Parameters Thin Ethernet Thick Ethernet Arc net
Cable Code RG-58 RG-8,RG-11 RG-62
Terminator value 50 Ohm 50 Ohm 93 Ohm
Segment Length 185 Mts. 500 Mts. N / A
Connectors used BNC,T-connector AUI BNC
Data transmission rate 10 Mbps 10 Mbps 2.5 Mbps
Topology Bus Bus Star
Comparison between types of Co-axial CablesComparison between types of Co-axial Cables
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2. Twisted Pair2. Twisted Pair
Twisted pair cable uses one or more pairs of two twisted Copper wires. The twists in twisted - pair cable decrease cross talk because radiated signals from the twisted wires tend to cancel each other out.
Types of twisted-pair cables:
1. UTP
2. STP
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1. UTP (Unshielded twisted pair)
2. UTP cable consists of four pairs of twisted solid copper wires. All four pairs are colour coded and is encased in a plastic outer casing.
Normally category 3 and 5 (commonly known as CAT-3 & CAT-5) are used for computer networks . CAT-3 is meant for data transmission rate of 10 Mbps whereas CAT-5 is meant for upto 100 Mbps.
Connectors used is RJ – 45.
Topology is Physical STAR- Logical BUS
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Categories of Unshielded Twisted Pair
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2. STP (Shielded twisted pair)
STP has two pairs of color coded conductors
wrapped in a foil shielding above this shielding a
plastic encasement is provided.
STP cables are made for upto 155 Mbps data
transmission rate.
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3. Fiber optic 3. Fiber optic
Fiber optic cable is made of light-conducting glass or plastic core surrounded by more glass called Cladding, and a tuff outer sheet . The centre core provides the light path or wave-guide while the cladding is composed of varying layers of reflective glass. The Glass cladding is designed to refract light back in to the core. Each core and cladding strand is surrounded by a tight or loose sheath . Current fiber optic technologies allow data rates from 100 Mbps to 2 Gbps. Connectors used is ST connectors
Two types of fiber optic cables are available
1. Single-mode fiber ( Segment length = 40 Kms.)
2. Multi-mode fiber ( Segment length = 2 Kms.)
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SMF (Single-mode Fiber)
Narrow core through which laser-generated light travels over one path, reflecting very little
Accommodates high bandwidths and long distances
Expensive
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MMF (Multimode Fiber)
Benefits over copper cabling:
Nearly unlimited throughput
Very high resistance to noise
Excellent security
Ability to carry signals for much longer distances before
requiring repeaters than copper cable
Industry standard for high-speed networking
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MMF (continued)
Throughput: transmission rates exceed 10 Gigabits per
second
Cost: most expensive transmission medium
Connector: 10 different types of connectors
Typically use ST or SC connectors
Noise immunity: unaffected by EMI
Size and scalability: segment lengths vary from
150 to 40,000 meters
Optical loss: degradation of light signal after it travels a
certain distance away from its source
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Cable Design and Management
Cable plant: hardware making up enterprise-wide cabling
system
Structured cabling: TIA/EIA’s 568 Commercial Building
Wiring Standard
Entrance facilities point where building’s internal cabling
plant begins
Demarcation point: division between service carrier’s
network and internal network
Backbone wiring: interconnection between
telecommunications closets, equipment rooms, and
entrance facilities
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Cable Design and Management (continued)
Structured cabling (continued): Equipment room: location of significant networking
hardware, such as servers and mainframe hosts
Telecommunications closet: contains connectivity for groups of workstations in area, plus cross connections to equipment rooms
Horizontal wiring: wiring connecting workstations to closest telecommunications closet
Work area: encompasses all patch cables and horizontal wiring necessary to connect workstations, printers, and other network devices from NICs to telecommunications closet
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Installing Cable
Many network problems can be traced to poor cable installation
techniques
Two methods of inserting UTP twisted pairs into RJ-45 plugs:
TIA/EIA 568A and TIA/EIA 568B
Straight-through cable allows signals to pass “straight through”
between terminations
Crossover cable: termination locations of transmit and receive wires
on one end of cable reversed
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Wireless Transmission
Networks that transmit signals through the atmosphere via
infrared or RF waves are known as wireless networks or
wireless LANs (WLANs)
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The Wireless Spectrum
Figure : The wireless spectrum
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Characteristics of Wireless Transmission
Figure : Wireless transmission and reception
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Antennas
Radiation pattern describes relative strength over three-
dimensional area of all electromagnetic energy the antenna
sends or receives
Directional antenna issues wireless signals along a single
direction
Omnidirectional antenna issues and receives wireless
signals with equal strength and clarity in all directions
Range: geographical area an antenna or wireless system
can reach
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Signal Propagation
Figure : Multipath signal propagation
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Signal Degradation
Fading: change in signal strength resulting from
electromagnetic energy being scattered, reflected, or
diffracted after being issued by transmitter
Wireless signals experience attenuation
May be amplified and repeated
Interference is significant problem for wireless
communications
Atmosphere saturated with electromagnetic waves
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Narrowband, Broadband, and Spread Spectrum Signals
Narrowband: transmitter concentrates signal energy at
single frequency or in very small range of frequencies
Broadband: uses relatively wide band of wireless spectrum
Offers higher throughputs
Spread spectrum: use of multiple frequencies to transmit a
signal
Frequency hopping spread spectrum (FHSS)
Direct sequence spread spectrum (DSSS)
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Fixed versus Mobile
Fixed wireless system: locations of transmitter and receiver
do not move
Point-to-point link
Efficient use of signal energy
Mobile wireless system: receiver can be located anywhere
within transmitter’s range
More flexible
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Infrared Transmission
Transmitted by frequencies in the 300-GHz to 300,000-GHz
range
Most often used for communications between devices in
same room
Relies on the devices being close to each other
May require line-of-sight path
Throughput rivals fiber-optics
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Wireless LAN (WLAN) Architecture
Figure : An ad-hoc WLAN
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Wireless LAN Architecture (continued)
Figure : An infrastructure WLAN
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Wireless LAN Architecture (continued)
Figure : Wireless LAN interconnection
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NETWORK COMPONENTS OVERVIEW
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Fundamentals of LAN
• Typically Ethernet based• Star topology oriented• UTP (twisted pair) and fiber media• Conforms to IEEE 802.3 standard• Works at 10, 100, 1024 Mbps• Reduced throughput as the nodes
increase (Collision)
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IEEE Standards
An association that promotes engineering and electronic
improvement
IEEE 802 was started in February 1980
IEEE 802 committee defines frames, speed, distances and types of
cabling to use for networking
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Protocols and Procedures
Protocols are set of rules which are used by the nodes on a network to
communicate with each other
Protocols are developed by committees, different companies developed products
confirming to those protocols
Standard Protocols
Ethernet Token Ring ARCnet
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LAN Architecture - I
802.3
Defines a standard for physical layer and data link layer of the Ethernet
architecture that uses wired connection
Ethernet is an architecture that mainly uses bus topology
Defines various cabling used for different types of topologies
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LAN Architecture - II
802.4
Defines a standard for Token Bus architecture
Token bus is similar to token ring, but it uses coaxial cables
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LAN Architecture - III
802.5
Defines a standard for Token ring architecture
Uses the 10 Base T cabling standard
Uses twisted pair cabling to connect devices instead of coaxial cable
Passes data from one computer to another like in a token bus network
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IEEE 802.3 Logical relationship with OSI Reference Model
IEEE 802.3 physical layer
corresponds to the OSI physical
layer
OSI data link layer is divided into two
IEEE 802 sublayers
The Media Access Control
(MAC) sublayer
The MAC-client sublayer
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Ethernet
Defined by IEEE as the 802.3 standard
Most widely adapted LAN technology
Supports data transfer rates of 10 Mbps, 100 Mbps and 1 Gbps
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Introduction to Ethernet
Three data rates currently defined for the operation over optical fiber and
twisted-pair cables
10 Mbps – 10Base-T Ethernet
100 Mbps - Fast Ethernet
1000 Mbps - Gigabit Ethernet
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Working of Ethernet
Ethernet frame is used to transfer data over a network
Each device in an Ethernet network is uniquely identified by a 48 bit
(6 bytes) address called Ethernet address
Ethernet addresses are represented as six pairs of hexadecimal
digits separated by a colon.
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Elements of Ethernet System
Elements of Ethernet System
MediumSet of Medium Access
Control RulesEthernet frame
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Ethernet Medium
Transmits information over the network
Computer D transmits information for
Printer C
Computer B and A also receives the
information
All device inspects the destination
address
If the received frame is not meant for
them, they will reject the frame
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Data Transmission
When a computer wants to transmit, it listens to the cable
(transmission medium)
If two or more devices simultaneously transmit data on an idle
cable, collision may occur
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Example of Collision
Each device decides to broadcast
an Ethernet frame to other device
Devices listens to the Ethernet
medium and detects that no
carrier is present
Devices transmit simultaneously,
causing a collision
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Carrier Sense Multiple Access/ Collision Detection (CSMA/CD)
Permits one device to access to the network media at a time to
avoid collision
Networks using CSMA/CD technology such as Ethernet, network
devices compete for the network media
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Working of CSMA/CD
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Carrier Sensing Multiple Access / Collision Avoidance (CSMA/CA)
Set of rules that can avoid collisions, unlike CSMA/CD that handles network
transmissions once collisions are detected
In CSMA/CA, all devices are forced to wait for a random number of time
slots and sense the medium again
If the medium is sensed to be busy, the device stops the timer until it
becomes free again.
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Token Ring - I
Token Ring is a network architecture developed by IBM
Also known as IEEE 802.5
Uses logical ring topology
Multiple MAUs can be connected to extend the ring
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Token Ring - II
Data transfer is facilitated with the help of token passing mechanism
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Token Ring - III
Speed is either 4 or 16 Mbps Performance is significantly faster than Ethernet networks Uses physical star topology Hides logical ring inside a hub, known as Multistation Access Unit (MAU) Unshielded Twisted Pair (UTP) or Shielded Twisted Pair (STP) cables are
used connect nodes to the hub
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Token Ring - IV
Advantages:
Data collision does not occur
Every station is allowed to
transmit data
Time required to carry the
amount of data can be
calculated
Minimum cable requirement
Disadvantages:
System collapses if links
between nodes are
malfunctioning
No alternative link to transmit the
data
Data transmission is through
single direction
Performance degrades when
junk data is transmitted
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Token Ring Vs Ethernet
Token Ring Ethernet
Token Ring network uses token passing
mechanism.
Ethernet network use CSMA/CD mechanism.
Physical star topology is used. Any topology can be used as physical
topology.
Defined by IEEE 802.5 standard. Defined by IEEE 802.3 standard.
Devices in token ring may transmit only at
specific time.
Devices can transmit as soon as the medium is
free.
Support heavy network traffic and maintains
the network performance.
The performance of the Ethernet network
degrades as network traffic increases.
Token Ring network is deterministic. Ethernet network is not deterministic as token
ring.
Token ring network provides bandwidth
efficiency up to 90%.
Ethernet network provides bandwidth
efficiency up to 40%.
The network setup and maintenance of token
ring is expensive than Ethernet.
The cost of network equipment is lower for
Ethernet.
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Types of Ethernet
Cabling Standards
10Base5 10Base2 10Base-T 10Base-F
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10Base-5
Thick coaxial cable is also referred to as thicknet 10Base5 refers to specifications of thick coaxial cable carrying Ethernet
signals The 5 refers to the maximum segment length being 500 meters RG-8 coaxial cable is used A 15-pin female DB connector called AUI connector is used to connect the
device
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10Base-2
10Base-2 (thin coaxial cable) is also referred to as thinnet In 10Base-2, “2” refers to approximate maximum segment length of the
cable which is 185 meters 10Base2 uses RG-58 coaxial cable with BNC connectors
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10Base-T
Allows stations to be attached via twisted pair cable 10 refers to the transmission speed of 10 Mbps “T” refers to twisted pair cable In a 10BaseT network, each computer (node) is connected to a hub
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10 Base-F
Uses fiber optics
Possesses excellent noise immunity and is the method of choice when
running between buildings or widely separated hubs
10 Base-F is expensive as the connectors and terminators used in 10
Base-F are costly
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5-4-3 Rule - I
Developed to limit the size of an Ethernet collision domain. Implemented by Ethernet (IEEE 802.3) for number of repeaters and
segments on shared access The rule states that: Any two nodes in the network should not be separated
by more than 5 segments, 4 repeaters and 3 populated segments
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Network using 5-4-3 rule
5 – Specifies that maximum 5 segments can be used in the network 4 – Specifies the number of repeaters/concentrators used to connect the
network segments 3 – Specifies the number of populated segments
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Comparing Ethernet Types
Ethernet types 10Base5 10Base2 10BaseT 10BaseF
Media Type Thick coaxial
(RG8)
Thin coaxial
(RG58)
UTP Fiber-optic
Max.segment
length
(meters)
500 185 100 1000
Frequency(MHZ) 10 10 10 10
Max
Nodes/Segme
nt
100 30 1024 1024k
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Extending the network
A computer network can be extended using repeaters, hubs and bridges
In computer networks, a bridge is an Internetworking device
Repeater regenerates signal
Repeaters remove the unwanted noise in an incoming signal
A hub is a multi port repeater which provides a common point for the
connection of network devices
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Introduction to Advanced Ethernet
Ethernet is most widely used network technology
Introduced by IEEE 802.3
Ethernet systems are 10Base-T and 10Base-FL
High speed Ethernet includes
100Base Ethernet
Gigabit Ethernet
Switched Ethernet
Full Duplex Ethernet
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Features of Advanced Ethernet
Advanced Ethernet would use a physical star to match the robustness of
Token ring
It would not use more expensive coaxial cables and adopt inexpensive UTP
cabling
It would use the same frame types and speeds of the older Ethernets so
that new Ethernets will be compatible with older ones
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10BASE-T - I
Ethernet standard known as twisted pair Ethernet
Uses a star bus topology
Stations are connected to a hub using pairs of twisted cables
Features:
Failure of one system does not affect entire network
Easy troubleshooting
Addition and removal of device does not affect network
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10BASE-T Topology
It uses a physical star topology in which each node connects to a central hub The hub is a multiport repeater. It receives the signal from one port, regenerates
it and passes the signal to all the other ports
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Meaning of 10BASE-T
10 refer to 10 Mbps transmission speed, Base is for baseband signaling and
T stands for twisted pair cable
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10Base T Specifications and Limitations
Specifications include:
Fault Tolerant
Easy Troubleshooting
Easy Moves and Changes
Limitations include:
Distance
Sensitive to noise
Number of computers connected
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10BASE-FL
Ethernet standard that operates over fiber optic cable and covers a distance up
to 2 k.m.
Multimode fiber and Straight Tip (ST) connector are used to build 10Base-FL
segment
10Base FL components
Network MediumMedium Attachment
Unit (MAU)
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5-4-3 Rule - I
Developed to limit the size of an Ethernet collision domain. Implemented by Ethernet (IEEE 802.3) for number of repeaters and
segments on shared access The rule states that: Any two nodes in the network should not be separated
by more than 5 segments, 4 repeaters and 3 populated segments
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5-4-3 Rule - II
Categories of physical segments:
User segments used to connect the systems in the network. These
segments are also known as populated segments.
Link segments used to connect repeaters in the network. These segments
are also known as unpopulated segments.
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Network using 5-4-3 rule
5 – Specifies that maximum 5 segments can be used in the network 4 – Specifies the number of repeaters/concentrators used to connect the
network segments 3 – Specifies the number of populated segments
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High Speed Ethernet
Developed to increase connectivity speed between the terminals or computers in a network.
Ethernet Standards
Fast Ethernet(100Base Ethernet)
Gigabit Ethernet 10-Gigabit Ethernet
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100Base Ethernet
Supports data transfer rate up to 100 Mbps Also called as Fast Ethernet Makes use of CAT 5 cable and fiber cable
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Advantages and Disadvantages
Advantages Speed – Ten times faster than regular 10Base-T network Throughput – Faster for video, multimedia, graphics, Internet surfing and
other applications that require high speed Disadvantages Mode of data transfer – 100Base-T4 Ethernet cannot support full duplex
mode of data transfer Wiring – 100Base-T4 requires four pair of wiring for data transfer
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Gigabit Ethernet
Supports data transfer rate up to 1000 Mbit/s
Also called as 1000BASE-T Ethernet
Gigabit Ethernet
Standards
1000Base-SX 1000Base-LX 1000Base-CX 1000Base-T 1000Base-TX
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10-Gigabit Ethernet - I
Was developed by IEEE 802.3ae in 2002.
Supports data transfer rate that is ten times faster than Gigabit ethernet
Compatible with Synchronous Optical Network (SONET)
Supports segment length up to 40 Kms
Uses Media Access Control (MAC) protocol
Uses full-duplex mode of transmission and mostly run on fiber
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10-Gigabit Ethernet - II
Standards included:
10GBASE-CX4
10GBASE-T
10GBASE-SR (Short Range)
10GBASE-LRM (Long Reach Multimode)
10GBASE-LR (Long Range)
10GBASE-ER (Extended Range)
10GBASE-LX4
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Summary of Physical Layer Standard
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Summary of Physical Layer Standard (Contd)
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Switched Ethernet
Employs a switch instead of a repeater or an Ethernet hub to connect
individual hosts or segments
Uses three types of switching:
Cut-through
Store and forward
Fragment-free
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Basic Structure of Switched Ethernet
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Full-Duplex Ethernet
Devices at both ends can send and receive data at the same time
Provides twice the bandwidth of normal (half duplex) Ethernet
Each pairs of wires acts as a separate channel and allows the devices at
each end to communicate with one another in full duplex mode
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Case Study
The MoneyMaker bank has recently upgraded its Ethernet network from 10Base-T to 100Base-T network. It has also changed its cabling from CAT5 to CAT6 straight through cables and 10 Mbps NIC cards are replaced with 10/100 Mbps for future compatibility. After upgradation, some computers in the accounts department of the bank are facing the slower connectivity problems.
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Problem
Identifying problem related to cabling and crimping of RJ-45 jack for new CAT6 cables.
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Suggested Solution
Check the crimping of RJ-45 connector and configure the NIC to operate in 100 Base full duplex mode.
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Summary
Information can be transmitted via two methods: analog or digital
In multiplexing, the single medium is logically separated into multiple channels, or sub channels
Throughput is the amount of data that the medium can transmit during a given period of time
Baseband is a form of transmission in which digital signals are sent through direct current pulses applied to the wire
Noise is interference that distorts an analog or digital signal
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Summary (continued)
Analog and digital signals may suffer attenuation
Cable length contributes to latency, as does the presence
of any intervening connectivity device
Coaxial cable consists of a central copper core surrounded
by a plastic insulator, a braided metal shielding, and an
outer plastic cover (sheath)
Twisted-pair cable consists of color-coded pairs of
insulated copper wires
There are two types of twisted-pair cables: STP and UTP
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Summary (continued)
There are a number of Physical layer specifications for
Ethernet networks
Fiber-optic cable provides the benefits of very high
throughput, very high resistance to noise, and excellent
security
Fiber cable variations fall into two categories: single-mode
and multimode
Structured cabling is based on a hierarchical design that
divides cabling into six subsystems
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Summary (continued)
The best practice for installing cable is to follow the TIA/EIA
568 specifications and the manufacturer’s
recommendations
Wireless transmission requires an antenna connected to a
transceiver
Infrared transmission can be used for short-distance
transmissions
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THANK YOU
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