全套英文版《计算机网络》ppt电子课件教案_1

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1、Chapter4:NetworkLayerChaptergoals:understandprinciplesbehindnetworklayerservices:routing(pathselection)dealingwithscalehowarouterworksadvancedtopics:IPv6,multicastinstantiationandimplementationintheInternetOverview:networklayerservicesroutingprinciple:pathselectionhierarch

2、icalroutingIPInternetroutingprotocolsreliabletransferintra-domaininter-domainwhat’sinsidearouter?IPv6multicastrouting14:NetworkLayerNetworklayerfunctionstransportpacketfromsendingtoreceivinghostsnetworklayerprotocolsineveryhost,routerthreeimportantfunctions:pathdeterminati

3、on:routetakenbypacketsfromsourcetodest.Routingalgorithmsswitching:movepacketsfromrouter’sinputtoappropriaterouteroutputcallsetup:somenetworkarchitecturesrequireroutercallsetupalongpathbeforedataflowsnetworkdatalinkphysicalnetworkdatalinkphysicalnetworkdatalinkphysicalnetwo

4、rkdatalinkphysicalnetworkdatalinkphysicalnetworkdatalinkphysicalnetworkdatalinkphysicalnetworkdatalinkphysicalapplicationtransportnetworkdatalinkphysicalapplicationtransportnetworkdatalinkphysical24:NetworkLayerNetworkservicemodelQ:Whatservicemodelfor“channel”transportingp

5、acketsfromsendertoreceiver?guaranteedbandwidth?preservationofinter-packettiming(nojitter)?loss-freedelivery?in-orderdelivery?congestionfeedbacktosender????virtualcircuitordatagram?Themostimportantabstractionprovidedbynetworklayer:serviceabstraction34:NetworkLayerVirtualcir

6、cuitscallsetup,teardownforeachcallbeforedatacanfloweachpacketcarriesVCidentifier(notdestinationhostOD)everyrouteronsource-destpathsmaintain“state”foreachpassingconnectiontransport-layerconnectiononlyinvolvedtwoendsystemslink,routerresources(bandwidth,buffers)maybeallocated

7、toVCtogetcircuit-likeperf.“source-to-destpathbehavesmuchliketelephonecircuit”performance-wisenetworkactionsalongsource-to-destpath44:NetworkLayerVirtualcircuits:signalingprotocolsusedtosetup,maintainteardownVCusedinATM,frame-relay,X.25notusedintoday’sInternetapplicationtra

8、nsportnetworkdatalinkphysicalapplicationtransportnetworkdatalinkphysical1.Initiatecall2.i