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1、RTP:ATransportProtocolforReal-TimeApplications1IntroductionThismemorandumspecifiesthereal-timetransportprotocol(RTP),whichprovidesend-to-enddeliveryservicesfordatawithreal-timecharacteristics,suchasinteractiveaudioandvideo.Thoseservicesincludepayloadtypeidentification,sequencenumb
2、ering,timestampinganddeliverymonitoring.ApplicationstypicallyrunRTPontopofUDPtomakeuseofitsmultiplexingandchecksumservices;bothprotocolscontributepartsofthetransportprotocolfunctionality.However,RTPmaybeusedwithothersuitableunderlyingnetworkortransportprotocols(seeSection10).RTPsu
3、pportsdatatransfertomultipledestinationsusingmulticastdistributionifprovidedbytheunderlyingnetwork.NotethatRTPitselfdoesnotprovideanymechanismtoensuretimelydeliveryorprovideotherquality-of-serviceguarantees,butreliesonlower-layerservicestodoso.Itdoesnotguaranteedeliveryorpreventou
4、t-of-orderdelivery,nordoesitassumethattheunderlyingnetworkisreliableanddeliverspacketsinsequence.ThesequencenumbersincludedinRTPallowthereceivertoreconstructthesender'spacketsequence,butsequencenumbersmightalsobeusedtodeterminetheproperlocationofapacket,forexampleinvideodecoding,w
5、ithoutnecessarilydecodingpacketsinsequence.WhileRTPisprimarilydesignedtosatisfytheneedsofmulti-participantmultimediaconferences,itisnotlimitedtothatparticularapplication.Storageofcontinuousdata,interactivedistributedsimulation,activebadge,andcontrolandmeasurementapplicationsmayals
6、ofindRTPapplicable.ThisdocumentdefinesRTP,consistingoftwoclosely-linkedparts:[1].Thereal-timetransportprotocol(RTP),tocarrydatathathasreal-timeproperties.[2].TheRTPcontrolprotocol(RTCP),tomonitorthequalityofserviceandtoconveyinformationabouttheparticipantsinanon-goingsession.Thela
7、tteraspectofRTCPmaybesufficientfor"looselycontrolled"sessions,i.e.,wherethereisnoexplicitmembershipcontrolandset-up,butitisnotnecessarilyintendedtosupportallofanapplication'scontrolcommunicationrequirements.Thisfunctionalitymaybefullyorpartiallysubsumedbyaseparatesessioncontrolpro
8、tocol,whichisbeyondthescopeofthis
