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Fundamentals of Networking
(Topic 1)
Textbook:
Networking Basics, CCNA 1 Companion Guide, Cisco Press
Cisco Networking Academy Program, CCNA 1 and 2,Companion Guide, Cisco Press, Latest Edition
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Common Networking Icons
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Networks
A network is a set of devices (nodes)connected by media links. A node can bea computer, printer, or any other device
capable of sending and/or receiving datagenerated by other nodes on the network.The links connecting the devices are oftencalled communication channels.
E.g. two PCs connected with a cable, theInternet
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Requirements for Internet
Connection Physical connection
Network Interface Card (NIC)
Cable? Wireless
Logical connection A logical connection uses standards call protocols
A protocol is a set of rules and conventions thatgovern how devices on a network communicate
Transmission Control Protocol / Internet Protocol(TCP/IP) is a key protocol used in the Internet
Applications E.g. Web Browsers
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PC Basics
Transistor, Integrated circuit (IC), Resistor, Capacitor,CPU, memory etc.
Motherboard, Power Supply, Hard disk, CDROM, VideoCard, Sound Card, etc.
Serial Port, USB Port, Parallel Port Modem
A modem is an electronic device that is used for datacommunications through telephone lines
Network Interface Card (NIC)
An expansion board that provides a network communicationconnection to and from a PC.
Build in circuit
10 Mbps, 100 Mbps, 1000 Mbps
Media Access Control (MAC) address
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Binary Representation of Data
Computers can only understand and use data
that is in binary (two-state, on/off, 0/1) format
Each binary digit is called a bit
Each grouping of eight bits is called a byte
Kilo (1024), Mega (1024*1024), Giga, Tera
American Standard Code for Information
Interchange (ASCII) is the most commonly usedcode for representing alphanumeric data in a
computer. E.g. 65 is A, 66 is B
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Base 10 Number System
Symbols: 0,1,2,3,4,5,6,7,8,9
2134 (decimal) = 2*103 + 1*102 + 3*101 + 4*100
Base
Exponent103 102 101 100
Place
Value1000 100 10 1
e.g. 2134 2*103 1*102 3*101 4*100
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Base 2 Number System
Symbols: 0,1
10110 (binary) = 1*24 + 1*22 + 1*21 = 22 (decimal)
Base
Exp27 26 25 24 23 22 21 20
Place
Value128 64 32 16 8 4 2 1
e.g.
10110
0 0 0 1 0 1 1 0
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Base 16 Number System
Symbols: 0,1,2,3,4,5,6,7,8,9,A,B,C,D,E,F
0A08 (hex) = 0*163 + 10*162 + 0*161 + 8*160
= 2568 (decimal)
Base
Exponent163 162 161 160
Place
Value4096 256 16 1
e.g. 0A08 0*163 10*162 0*161 8*160
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Converting Decimal Numbers to
Binary Numbers
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Converting Binary Numbers to
Decimal Numbers
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Converting Decimal to
Hexadecimal
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Converting Hexadecimal to
Decimal
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Converting Binary to Hexadecimal
Binary -> Decimal -> Hexadecimal
Short Cut: 4 bits -> 1 Hexadecimal digit
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Basic Logic Operations
AND OR XOR
0 0 0 0 0
0 1 0 1 1
1 0 0 1 1
1 1 1 1 0
NOT
0 1
1 0
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Types of Networks
Local Area Network (LAN) LAN is usually privately owned and links the devices
in a single office, building, or campus
Designed to allow resources to be shared
Metropolitan Area Network (MAN) Designed to extend over an entire city
May involve service provided by public companies,e.g. local telephone company
Wide Area Network (WAN) Provides long-distance transmission of data overlarge geographical areas
Virtual Private Network (VPN), Intranet etc.
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Local Area Network (LAN)
Designed to
Operate within a limited geographic area
Allow many users to access high-bandwidth media
Provide full-time connectivity to local services
Connect physically adjacent devices
Some common LAN technologies
Ethernet
Token Ring
FDDI
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Wide Area Network (WAN)
Designed to Operate over large, geographically separated areas
Allow users to engage in real-time communicationwith other users
Provide full-time remote resources connected to localservices
Provide e-mail, WWW, file transfer, e-commerceservices
Some common WAN technologies Modems, ISDN,
DSL, Frame Relay
T1 or E1 leased lines
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Virtual Private Network (VPN)
A VPN is a private network that is
constructed within a public network
infrastructure (e.g. Internet)
Provides a secure tunnel
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Bandwidth
The amount of information that can flow througha network connection in a given period of time.
Analogy: the width of a pipe, the number oflanes on a highway
Measurement: bps
Why important Bandwidth is finite
Bandwidth is not free
Bandwidth is a key factor in analyzing networkperformance and designing new networks
Demand for bandwidth is ever-increasing
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Throughput
Bandwidth of a LAN is usually 100Mbps,
can you transfer file at that rate?
Throughput refers to actual measuredbandwidth
Factors
Client, Server, Other users, Routing,
Topology, Type of data, Time of day
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Network Protocols (1)
Protocol suites are collections of protocols that
enable network communication from one host
through the network to another host
A protocol is a formal description of a set of rulesand conventions that govern a particular aspect
of how devices on a network communicate. It
determines the format, timing, sequencing, and
error control
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Network Protocols (2)
Protocols are created and maintained by many
Standards organizations and committees
Institute of Electrical and Electronic Engineers (IEEE)
American National Standards Institute (ANSI)
Telecommunications Industry Association (TIA)
Electronic Industries Alliance (EIA)
International Telecommunications Union (ITU)
International Organization of Standardization (ISO)
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Networking Models
Conceptual Model helps you understand the action that occurs during
communication from one computer to another
Network communications is a very complex process,
difficult to understand it as a whole, so break it down intoa series of layers
Each layer is responsible for a specific part of networkcommunication
Layers interact with the layer above and below them only
Two common models Open System Interconnection (OSI) reference model
TCP/IP reference model
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OSI Model (1)
Released in 1984, by ISO
Provides vendors with a set of standardsthat ensure greater compatibility andinteroperability among various types ofnetwork technologies
Defines the network functions that occur at
each layer Acts as a framework for understanding the
network
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OSI Model (2)
7 layers 7: Application layer
6: Presentation layer
5: Session layer
4: Transport layer
3: Network layer
2: Data link layer
1: Physical layer
Layer 5,6,7 are concerned with applicationissues
Layer 4,3,2,1 are concerned with data-transportissues
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OSI Model (3)
Advantages of layering
Standardizes network components to allow
multiple-vendor development and support
Allows different types of network hardware
and software to communicate
Prevents changes in one layer from affecting
the other layers Breaks into smaller components to make
learning easier
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Layer 7: Application Layer
Closest to the user
Provides network services to the users
applications E.g. telnet, http
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Layer 6: Presentation Layer
Ensures that the information that the application
layer of one system sends out can be read by
the application layer of another system
Provides services to layer 7
Translates (if need) among multiple data formats
by using a common format
Encryption and Decryption E.g. layer 6 formats: TIFF, JPEG, MIDI, MPEG
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Layer 5: Session Layer
Establishes, manages, and terminates
sessions between two communicating
hosts
Synchronizes dialogue between the two
hosts presentation layers and manages
their data exchange
Provides services to layer 6
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Layer 4: Transport Layer
Segments data from the sending hosts system andreassembles it into data stream on the receiving hostssystem
Provides a data-transport service which handles issues
like Reliability of transport Establishment, maintenance, and proper termination of Virtual
circuits
Transport error detection, recovery, Information flowcontrol
Provides services to layer 5 E.g. Transmission Control Protocol (TCP), User
Datagram Protocol (UDP), Sequenced Packet Exchange(SPX)
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Layer 3: Network Layer
Provides connectivity and path selection
(routing) between two host systems that
might be on separated networks
Concerned with logical addressing
Provides services to layer 4
E.g. Internet Protocol (IP), InternetworkPacket Exchange (IPX)
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Layer 2: Data Link Layer
Provides reliable transit of data across aphysical link
Concerned with physical address, network
topology, network access, error notification,ordered delivery of frames, and flowcontrol
Provides services to layer 3 E.g. protocols include Ethernet, Token
Ring, ISDN, PPP, and Frame Relay
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Layer 1: Physical Layer
Defines the electrical, mechanical,
procedural, and functional specifications
for activating, maintaining, and
deactivating the physical link between end
systems
E.g. voltage levels, timing of signal,
physical data rates, physical connectors,etc.
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Peer-to-Peer Communications
Each layer of the OSI model at the source mustcommunicate with its peer layer at thedestination
The protocols at each layer exchangeinformation, called protocol data units (PDU),between peer layers
Layer 4 (Segments)
Layer 3 (Packets) Layer 2 (Frames)
Layer 1 (Bits)
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Encapsulation
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De-Encapsulation
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Networking Devices (1)
Network Interface Card (NIC) Each carries a unique code, Media Access Control (MAC)
address
Repeaters
To regenerate and retime network signals, allowing them totravel a longer distance on the medium
Work at Layer 1, physical layer, of the OSI reference Model
Hubs To regenerate and retime signals, a common connection point
for devices in a network Connect segments of a LAN
No filtering, no switching, no routing
Work at Layer 1
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Networking Devices (2)
Bridges A Layer 2 device designed to create two or more LAN
segments, each of which is a separate collisiondomain
To filter traffic on a LAN to keep local traffic local(using MAC address) yet allow connectivity to othersegments
More intelligent than hubs, with filtering capability
Create more collision domains, allowing more than
one device to transmit simultaneously without causinga collision
Maintain MAC address tables (bridge tables)
Broadcast: to all segments, i.e. one broadcast domain
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Networking Devices (3)
Layer 2 Switches
Like bridges, switches connect LAN segments, use a
table of MAC addresses to determine the on which a
frame needs to be transmitted, and reduce traffic Operate at much higher speeds than bridges
(performed in hardware)
Consider each switch port is a microbridge, and gives
each host the mediums full bandwidth
(microsegmentation)
Broadcast: to all segments, i.e. one broadcast domain
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Switch
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Networking Devices (4)
Routers
Internetworking device that passes data
packets between networks based on Layer 3
addresses
Make decisions regarding the best path for
delivery of data (based on network addresses)
Examine incoming packets (Layer 3 data) Choose the best path
Switch them to the proper outgoing port
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Networking Devices (4)
Voice gateway
For handling packetized voice and data traffic
Digital Subscriber Line Access Multiplexers
(DSLAMs) Used at the service providers central office for
concentrating DSL modem connections from homes
Cable Modem
Wireless Access Point
Many more
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Network Topologies (1)
A network topology defines how computers,printers, network devices, and other devices areconnected
Describes the layout of the wire and devices and
the paths used by data transmissions Physical Topology
Refers to the physical layout of the devices andmedia
Bus, Ring, Star, Extended Star, Hierarchical, Mesh Logical Topology
Defines how the medium is accessed by the hostssending data
Broadcast, Token passing
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Network Topologies (2)
Bus
Connects all the devices using a single cable
Main cable segment must end with a
terminator
Adv?
Disadv?
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Network Topologies (3)
Star
Made up of a central connection point that is a
device such as hub, switch, or router, where
all the cabling segments meet. Each host inthe network is connected to the central device
with its own cable
Commonly used in Ethernet LANs
Adv?
Disadv?
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Network Topologies (4)
Ring Hosts are connected in a circle
Data frame travels around the ring, stopping at eachnode. If a node wants to transmit data, it adds dataand the destination address to it. The frame thencontinues around the ring until it reaches thedestination node, which takes the data out.
Adv: no collision
Single Ring (one direction) Vs Dual Ring (bothdirections, fault tolerance)
Usually logical in ring but physical in star
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Network Topologies (5)
Full-Mesh and Partial-Mesh
Full-mesh topology connects all devices to
each other for redundancy and fault tolerance
Adv?
Disadv?
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Network Topologies (6)
Logical Topology
How the hosts communicate across the medium
Broadcast
Data frame is broadcasted to all hosts No order that the stations must follow to use the network
Collision?
Token ring
Control network access by passing an electronic token
sequentially to each host
The host gets an empty token has the right to send data