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中科大,计算机网络课件13.ppt

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Chapter13Figure13.1TCP/IPprotocolsuiteSCTPisamessage-oriented,reliable protocolthatcombinesthe goodfeaturesofUDPandTCP.Table13.1SomeSCTPapplicationsFigure13.2Multiple-streamconceptAnassociationinSCTPcaninvolvemultiplestreams.Figure13.3MultihomingconceptSCTPassociationallowsmultipleIPaddressesforeachend. SCTP关联允许每一端使用多个IP地址全双工通信 面向连接的服务 面向连接强调建立关联（/协商），数据传送，关联终止。 无连接。 可靠的服务 确认机制，可靠也是面向连接的一个特点。InSCTP,adatachunkisnumberedusingaTSN.传输序号 不考虑传输层分片，从进程来的报文跟SCTP分组的数据块可以是一一对应的。Todistinguishbetweendifferentstreams,SCTPusesaSI.流标识符Todistinguishbetweendifferentdatachunksbelongingtothesamestream,SCTPusesSSNs.流序号Figure13.4ComparisonbetweenaTCPsegmentandanSCTPpacketTCPhassegments;报文段 SCTPhaspackets. 分组InSCTP,controlinformationanddatainformationarecarriedinseparatechunks.Figure13.5Packet,datachunks,andstreamsDatachunksareidentifiedbythreeidentifiers:TSN,SI,andSSN. TSNisacumulativenumberidentifyingtheassociation;SIdefinesthestream;SSNdefinesthechunkinastream.InSCTP,acknowledgmentnumbersareusedtoacknowledgeonlydatachunks;controlchunksareacknowledgedbyothercontrolchunksifnecessary.Figure13.6SCTPpacketformatInanSCTPpacket,controlchunkscomebeforedatachunks.Figure13.7GeneralheaderFigure13.8CommonlayoutofachunkChunksneedtoterminateona32-bit(4byte)boundary.Table13.2ChunksThenumberofpaddingbytesarenotincludedinthevalueofthelengthfield. 长度字段值不包含填充的字节数Figure13.9DATAchunkADATAchunkcannotcarrydatabelongingtomorethanonemessage,butamessagecanbesplitintoseveralchunks.ThedatafieldoftheDATAchunkmustcarryatleastonebyteofdata,whichmeansthevalueoflengthfieldcannotbelessthan17.Figure13.10INITchunkNootherchunkcanbecarriedinapacketthatcarriesanINITchunk.Figure13.11INITACKchunkNootherchunkcanbecarriedinapacketthatcarriesanINITACKchunk.Figure13.12COOKIEECHOchunkFigure13.13COOKIEACKFigure13.14SACKchunkFigure13.15HEARTBEATandHEARTBEATACKchunksFigure13.16SHUTDOWN,SHUTDOWNACK,andSHUTDOWNCOMPLETEchunksFigure13.17ERRORchunkTable13.3ErrorsFigure13.18ABORTchunkAconnectioninSCTPiscalledanassociation.Figure13.19Four-