计算机网络 Chapter3

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1、TransportLayer3-1Chapter3TransportLayerComputerNetworking:ATopDownApproach4thedition.JimKurose,KeithRossAddison-Wesley,July2007.TransportLayer3-2Chapter3:TransportLayerOurgoals:understandprinciplesbehindtransportlayerservices:multiplexing/demultiplexingrel

2、iabledatatransferflowcontrolcongestioncontrollearnabouttransportlayerprotocolsintheInternet:UDP:connectionlesstransportTCP:connection-orientedtransportTCPcongestioncontrolTransportLayer3-3Chapter3outline3.1Transport-layerservices3.2Multiplexinganddemultiplexi

3、ng3.3Connectionlesstransport:UDP3.4Principlesofreliabledatatransfer3.5Connection-orientedtransport:TCPsegmentstructurereliabledatatransferflowcontrolconnectionmanagement3.6Principlesofcongestioncontrol3.7TCPcongestioncontrolTransportLayer3-4Transportservicesa

4、ndprotocolsprovidelogicalcommunicationbetweenappprocessesrunningondifferenthoststransportprotocolsruninendsystemssendside:breaksappmessagesintosegments,passestonetworklayerrcvside:reassemblessegmentsintomessages,passestoapplayermorethanonetransportprotocolava

5、ilabletoappsInternet:TCPandUDPapplicationtransportnetworkdatalinkphysicalapplicationtransportnetworkdatalinkphysicallogicalend-endtransportTransportLayer3-5Transportvs.networklayernetworklayer:logicalcommunicationbetweenhoststransportlayer:logicalcommunicatio

6、nbetweenprocessesrelieson,enhances,networklayerservicesHouseholdanalogy:12kidssendinglettersto12kidsprocesses=kidsappmessages=lettersinenvelopeshosts=housestransportprotocol=AnnandBillnetwork-layerprotocol=postalserviceTransportLayer3-6Internettransport-layer

7、protocolsreliable,in-orderdelivery(TCP)congestioncontrolflowcontrolconnectionsetupunreliable,unordereddelivery:UDPno-frillsextensionof“best-effort”IPservicesnotavailable:delayguaranteesbandwidthguaranteesapplicationtransportnetworkdatalinkphysicalnetworkdatal

8、inkphysicalnetworkdatalinkphysicalnetworkdatalinkphysicalnetworkdatalinkphysicalnetworkdatalinkphysicalnetworkdatalinkphysicalapplicationtransportnetworkdatalinkphysicallogicalend-endtran