高级计算机网络 传输层ppt课件.ppt

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1、Lecture5:TheTransportLayer(BasicPrinciples)AdvancedComputerNetworkYangQinDepartmentofComputerScienceShenzhenGraduateSchoolHarbinInstituteofTechnologyTheTransportServiceServicesProvidedtotheUpperLayersTransportServicePrimitivesBerkeleySocketsAnExampleofSocketProgramming:AnInternetF

2、ileServerServicesProvidedtotheUpperLayersThenetwork,transport,andapplicationlayers.TransportServicePrimitivesTheprimitivesforasimpletransportservice.TransportServicePrimitives(2)ThenestingofTPDUs,packets,andframes.TransportServicePrimitives(3)Astatediagramforasimpleconnectionmanage

3、mentscheme.Transitionslabeledinitalicsarecausedbypacketarrivals.Thesolidlinesshowtheclient'sstatesequence.Thedashedlinesshowtheserver'sstatesequence.BerkeleySocketsThesocketprimitivesforTCP.SocketProgrammingExample:InternetFileServerClientcodeusingsockets.6-6-1SocketProgrammingExa

4、mple:InternetFileServer(2)Servercodeusingsockets.ElementsofTransportProtocolsAddressingConnectionEstablishmentConnectionReleaseFlowControlandBufferingMultiplexingCrashRecoveryTransportProtocol(a)Environmentofthedatalinklayer.(b)Environmentofthetransportlayer.AddressingTSAPs,NSAPsa

5、ndtransportconnections.ConnectionEstablishmentHowauserprocessinhost1establishesaconnectionwithatime-of-dayserverinhost2.ConnectionEstablishment(cont.)Threeprotocolscenariosforestablishingaconnectionusingathree-wayhandshake.CRdenotesCONNECTIONREQUEST.(a)Normaloperation,(b)OldCONNECT

6、IONREQUESTappearingoutofnowhere.(c)DuplicateCONNECTIONREQUESTandduplicateACK.ConnectionReleaseAbruptdisconnectionwithlossofdata.ConnectionRelease(2)Thetwo-armyproblem.ConnectionRelease(3)Fourprotocolscenariosforreleasingaconnection.(a)Normalcaseofathree-wayhandshake.(b)finalACKlost

7、.6-14,a,bConnectionRelease(4)(c)Responselost.(d)ResponselostandsubsequentDRslost.6-14,c,dFlowControlandBuffering(a)Chainedfixed-sizebuffers.(b)Chainedvariable-sizedbuffers.(c)Onelargecircularbufferperconnection.Multiplexing(a)Upwardmultiplexing.(b)Downwardmultiplexing.CrashRecovery

8、Differentcombinationsofcli