Computer Networks86097

《Computer Networks86097》由会员上传分享，免费在线阅读，更多相关内容在行业资料-天天文库。

1、ComputerNetworksNetworkLayerTopicsIntroductionRoutingCongestionControlInternetworkingTheInternetIntroductiontoNetworkLayerGettingpacketsfromsourcetodestinationmayrequiremanyhopsdatalinklayerfromoneendofwiretoanotherMustknowtopologyofsubnetAvoidoverloadingroutesDealwithdif

2、ferentnetworksNetworkLayerServicesServicestoTransportLayerOftencarriertocustomerverywelldefinedGoalsservicesindependentofsubnettechnologyshieldtransportlayerfromtopologyuniformnumberofnetworkaddesses,acrossLANsorWANSLotsoffreedom,buttwofactions:connection-orientedandconnec

3、tionlessConnectionlessInternetcamp30yearsofexperiencewithrealnetworkssubnetisunreliable,nomatterhowwelldesignedhostsshouldacceptthisanddoerrorcontrolandflowcontrolSEND_PACKETandRECV_PACKETeachpacketfullinformationnoordering,flowcontrolsincewillberedundantConnectionOriented

4、Telephonecompanycamp100yearsofinternationalexperiencesetupconnectionbetweenendhostsnegotiateaboutparameters,qualityandcostcommunicateinbothdirectionsallpacketsdeliveredinsequencesomemightstillbelostflowcontroltohelpslowsendersConnectedvsConnectionlessReally,wheretoputtheco

5、mplexitytransportlayer(connectionless)computerscheapdon’tclutternetworklayersincerelieduponforyearssomeapplicationsdon’twantallthoseservicessubnet(connected)mostusersdon’twantcomplexprotocolsontheirmachinesembeddedsystemsdon’treal-timeservicesmuchbetteronconnected(Un)Conne

6、cted,(Un)Reliable4classes,buttwomostpopularInternalOrganizationVirtualCircuitdonotchoosenewrouteperpacketestablishrouteandre-useterminateroutewhenterminateconnectionDatagramsnoadvancerouteseachpacketroutedindependentlymoreworkbutmorerobustSummaryComparisonExamplesofService

7、sRoutingAlgorithmscorrectnessandsimplicity(obviously)robustnesspartscanfail,butsystemshouldnottopologycanchangestabilityfairnessandoptimalityconflict!ReviewDescribeeachofthefollowingintermsofnetworklayersRepeaterHubBridgeRouterOptimalityvs.FairnessWhattooptimize?Minimizede

8、layMaximizenetworkthroughputButbasicqueuingtheorysaysifsystemnearcapacitythenlongdelays!C