Basics Of Comuter Networking

Basics Of Comuter Networking

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  Basics of ComputerNetworkingProf. Anish Goel
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  ContentsIntroductionHistory of CommunicationComputerNetworksCurrent ScenarioComplexityLayered ArchitectureComputer Networks
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  IntroductionWhere do yousee computers ?What is the purpose of connecting them in network ?Transmission from Analog to Digital Communication.Impact of computers on the communication methods.Most common form of communication ???Magic number of 64Kbps !!!!Computer Networks
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  Telephone Networks andCircuit SwitchingSignal for “ae” as in catMicrophoneLoudspeakeranalogelectricalsignalsoundsoundAlexander Graham Bell (1875) working on harmonic telegraph to multiplex telegraph signalsDiscovered voice signals can be transmitted directlyMicrophone converts voice pressure variation (sound) into analogous electrical signalLoudspeaker converts electrical signal back into sound Telephone patent granted in 1876Bell Telephone Company founded in 1877Computer Networks
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  The N2 Problem12N.. .34For N users to be fully connected directlyRequires N(N – 1)/2 connections Requires too much space for cablesInefficient & costly since connections not always onN = 1000N(N – 1)/2 = 499500Computer Networks
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  Circuit SwitchingPatch cordpanel switch invented in 1877Operators connect users on demandEstablish circuit to allow electrical current to flow from inlet to outletOnly N connections required to a central officeComputer Networks
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  Digitization of TelephoneNetworkPulse Code Modulation digital voice signalVoice gives 8 bits/sample x 8000 samples/sec = 64x103 bpsTime Division Multiplexing for digital voiceT-1 multiplexing (1961): 24 voice signals = 1.544x106 bpsDigital Switching (1980s)Switch TDM signals without conversion to analog formDigital Cellular Telephony (1990s)Optical Digital Transmission (1990s)One OC-192 optical signal = 10x109 bpsOne optical fiber carries 160 OC-192 signals = 1.6x1012 bps!All digital transmission, switching, and controlComputer Networks
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  Computer Connection ControlComputerSwitchconnectsInlets to Outlets. . .. . .VoiceA computer controls connection in telephone switchComputers exchange signaling messages to:Coordinate set up of telephone connectionsTo implement new services such as caller ID, voice mail, . . .To enable mobility and roaming in cellular networks“Intelligence” inside the networkA separate signaling network is requiredComputer Networks
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  Computer Network EvolutionOverview1950s: Telegraph technology adapted to computers 1960s: Dumb terminals access shared host computer1970s: Computers connect directly to each otherARPANET packet switching networkTCP/IP internet protocolsEthernet local area network1980s & 1990s: New applications and Internet growthCommercialization of InternetE-mail, file transfer, web, P2P, . . .Internet traffic surpasses voice trafficComputer Networks
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  What is aprotocol?Communications between computers requires very specific unambiguous rulesA protocol is a set of rules that governs how two or more communicating parties should interactInternet Protocol (IP)Transmission Control Protocol (TCP)HyperText Transfer Protocol (HTTP)Simple Mail Transfer Protocol (SMTP)Computer Networks
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  Computer-to-Computer NetworksAs costof computing dropped, terminal-oriented networks viewed as too inflexible and costlyNeed to develop flexible computer networksInterconnect computers as requiredSupport many applicationsApplication ExamplesFile transfer between arbitrary computersExecution of a program on another computerMultiprocess operation over multiple computersComputer Networks
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  Packet SwitchingMessage SwitchingTransferarbitrary message sizeBut in store-and-forward operation, long messages induce high delay on interactive traffic that consists of short messagesPacket switching introducedNetwork transfers packets using store-and-forwardPackets have maximum lengthBreak long messages into multiple packetsLow delays for interactive trafficARPANET testbed led to many innovationsComputer Networks
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  Current ScenarioHigh-speed datatransmission.More bandwidth.Multimedia traffic increasing.Wi-Fi and Wi-Max.ATM Networks.Optical Bandwidth Exploration.Speed limitation on electronic switching.Computer Networks