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Introduction
Computer Networks
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Motivation and Scope
Computer networks and internets: an overview of concepts, terminology
and technologies that form the basis for digital communication in private corporate networks the the global
Internet.
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Motivation for Networks
Information AccessSharing of ResourcesFacilitate Communications
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What a Network Includes
Transmission hardwareSpecial-purpose hardware devices
interconnect transmission media control transmission run protocol software
Protocol software encodes and formats data detects and corrects problems
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What a Network Does
Provides communication that is Reliable Fair Efficient From one application to another
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What a Network Does [continued]
Automatically detects and corrects Data corruption Data loss Duplication Out-of-order delivery
Automatically finds optimal path from source to destination
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Data Communication versus Networking
With only two nodes, mostly EE issues.
With more than two nodes, lot more issues!
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Direction of Transmission
Point to Point Broadcast
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Network Topologies
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Transmission Media
Wireline String Garden Hose Copper
Twisted PairCoax
Optical Fiber
Wireless Sound Light and mirrors Infrared RF Microwave
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Network Scope
Local Area Network (LAN)Metropolitan Area Network (MAN)Wide Area Network (WAN)
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Data Transmission
Serial
Parallel
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Multiplexing
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Communication Modes
SimplexHalf-duplexFull-duplex
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Connection-oriented versus Connectionless
Connection SetupData TransferConnection
Termination
Data Transfer
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Circuit Switching versus Packet Switching
Dedicated fixed bandwidth route fixed at setup idle capacity
wasted network state
Best Effort end-to-end control multiplexing
technique re-route capability congestion
problems
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Examples
Public Switched Telephone NetworkInternetPostal ServiceTrainCar and highway system
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Standards
HardwareSoftwareProtocolsAdvantages and DisadvantagesProprietary, De Facto, De JureStandards Bodies
IETF, IEEE, OSI, ANSI, ATM Forum, etc.
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Protocols
Rules, standards and etiquetteMetric SystemEnglishDinner partyMorse CodeTCP/IPHTML
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Layering
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Headers, Data and Trailers
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Encapsulation
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ISO OSI Reference Model
7: Application Layer6: Presentation Layer5: Session Layer4: Transport Layer3: Network Layer2: Data link Layer1: Physical Layer
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Interfaces and Services
PDUsSDUsSAPsPeer communicationsService Primitivesetc... read Tanenbaum 1.3.3 and
1.3.5
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TCP/IP Model
5: Application Layer4: Transport Layer3: Network Layer2: Data link Layer1: Physical Layer
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OSI versus TCP/IP
“Rough consensus and running code”
SimplicityTime to marketAvailability
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Network Classification
Physical medium: copper, fiber, wireless
Scope: LAN, MAN, WANTopology: bus, star, ring, meshSwitching style: circuit, packetApplication: voice, data, videoProtocol: IP, OSI, Ethernet, ATMTransmission rate: 10Mb/s, Gigabit
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Terms I (we) Often Use
Frames: think data link layerPackets: think network layerDatagrams: think IPSegments: think TCPCells: think ATMLayer <x>: refer to reference
models
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The End-to-End Argument
“End-to-End Arguments in System Design” J.H. Saltzer, D.P. Reed, and D.D. Clark http://web.mit.edu/Saltzer/www/
publications/