NetworkLayer:RoutingGoals:worklayerservices:routing(pathselection)worklayerservicesroutingprinciple:routingprotocols:intra-domaininter-worklayerprotocolsineveryhost,routerthreeimportantfunctions:pathdetermination::movepacketsfromrouter’sinputtoappropriaterouteroutput(.)callsetup:workservicemodelQ:Whatservicemodelfor“channel”transportingpacketsfromsendertoreceiver?guaranteedbandwidth?preservationofinter-packettiming(nojitter)?loss-freedelivery?in-orderdelivery?congestionfeedbacktosender????virtualcircuitordatagram?worklayer:workLayerVirtualcircuitscallsetup,teardownforeachcallbeforedatacanfloweachpacketcarriesVCidentifier(notdestinationhostID)everyrouteronsource-destpathsmaintain“state”foreachpassingconnectionlink,routerresources(bandwidth,buffers)maybeallocatedtoVCtogetcircuit-likeperf.“source-to-destpathbehavesmuchliketelephonecircuit”performance-workactionsalongsource-to-workLayerVirtualcircuits:signalingprotocolsusedtosetup,maintainteardownVCusedinATM,frame-relay,’Cisco’:worklayerrouters:nostateaboutend-to-work-levelconceptof“connection”packetstypicallyroutedusingdestinationhostIDpacketsbetweensamesource-(inferredvialoss)nocongestionnocongestionyesnoGuarantees?modelbeingextended:Intserv,workLayerRoutingGraphabstractionforroutingalgorithms:graphnodesareroutersgraphedgesarephysicallinkslinkcost:delay,$cost,orcongestionlevelsinglecostGoal:determine“good”path(sequenceofrouters)“good”path:typicallymeansminimumcostpathotherdef’workLayerRoutingAlgorithmclassificationGlobalordecentralizedinformation?Global:pletetopology,linkcostin
路由协议 来自淘豆网m.daumloan.com转载请标明出处.
