网络基础3-传输层.ppt

OSI传输层网络基础——第3章学****目标解释传输层的需求;确定传输层在终端应用程序之间传输数据的过程中所扮演的角色;描述两种TCP/IP传输层协议—TCP和UDP协议的作用。解释传输层的关键功能,包括可靠性、端口寻址以及数据分段;解释TCP和UDP协议如何发挥各自的关键功能;确定TCP或UDP协议的应用场合,并举出使用每个协议的应用程序的例子。————’worklayer:datatransferbetweenendsystemstransportlayer:datatransferbetweenprocessesrelieson,workdatalinkphysicallogicalend-:segment-unitofdataexchangedbetweentransportlayerentitiesakaTPDU:transportprotocoldataunitreceiverHtHnDemultiplexing:workP1MMMP3P4segmentheaderapplication-layerdataMultiplexing/demultiplexingmultiplexing/demultiplexing:basedonsender,receiverportnumbers,IPaddressessource,destport#sineachsegmentrecall:well-knownportnumbersforspecificapplicationsgatheringdatafrommultipleappprocesses,envelopingdatawithheader(laterusedfordemultiplexing)sourceport#destport#32bitsapplicationdata(message)otherheaderfieldsTCP/UDPsegmentformatMultiplexing: