Chapter 3_Transport Layer传输层

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1、2013/9/18内容提要•传输层提供的服务Chapter3•传输层的功能•无连接服务与面向连接服务•传输层寻址与端口•传输层复用/分解•无连接的传输协议——UDP•可靠数据传输的原理TransportLayer•停止-等待协议•回退N协议传输层•选择重传协议•滑动窗口协议•面向连接的传输协议——TCP•TCP报文段•TCP的可靠传输•TCP的流量控制•TCP的连接管理3:TransportLayer2•TCP的拥塞控制ContentsContents•Transport-layerservices•Transport-layerservices•Functionsofthetransport

2、layer•Functionsofthetransportlayer•ConnectionlessandConnection-orientedservices•ConnectionlessandConnection-orientedservices•Transportlayeraddressingandport•Transportlayeraddressingandport•Transportlayermultiplexing/de-multiplexing•Transportlayermultiplexing/de-multiplexing•Connectionlesstransportpr

3、otocol:UDP•Connectionlesstransportprotocol:UDP•Principlesofreliabledatatransfer•Principlesofreliabledatatransfer•Stop-and-wait•Stop-and-wait•Go-back-N•Go-back-N•Selectiverepeat•Selectiverepeat•Sliding-window•Sliding-window•Connection-orientedtransportprotocol:TCP•Connection-orientedtransportprotocol

4、:TCP•TCPsegmentstructure•TCPsegmentstructure•TCPreliabledatatransfer•TCPreliabledatatransfer•TCPflowcontrol•TCPflowcontrol•TCPconnectionmanagement•TCPconnectionmanagement•TCPcongestioncontrol•TCPcongestioncontrol3:TransportLayer33:TransportLayer4FunctionsofthetransportlayerFunctionsofthetransportlay

5、er•providelogicalcommunicationapplicationtransportbetweenappprocessesrunningnetworkdatalinkondifferenthosts为运行在不physical同主机上的应用进程之间提供逻辑通信–end-to-endcommunication端到端的通信–reliesonandenhancesnetworklayerservicesapplicationtransport依赖、强化网络层服务networkdatalink–从“点-点”通信到“端-端”physical通信是一次质的飞跃，为此传输层需要引入很多新的概念

6、和机制。3:TransportLayer53:TransportLayer612013/9/18TPDU结构与IP分组、帧结构的关系Contents•Transport-layerservices•传输层之间传输的报文称为传输协议数据TPDU•Functionsofthetransportlayer•ConnectionlessandConnection-orientedservices•TPDU有效载荷是应用层的数据•Transportlayeraddressingandport•Transportlayermultiplexing/de-multiplexing•传输层在有效载荷TPDU之

7、前加上TPDU头，就•Connectionlesstransportprotocol:UDP形成了TPDU传输协议数据单元。•Principlesofreliabledatatransfer•Stop-and-wait•Go-back-N•Selectiverepeat•Sliding-window•Connection-orientedtransportprotocol:TCP•TCPsegme