docsis3 组播转发机制要点分析

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1、DOCSIS3.0组播转发机制要点分析眩晕的猫2013081、Docsis3.0MDF设计核心思想：RemovingtheIGMPcontrolplanefromtheCMofferswiderangeofbenefitsasfollows:•EnsureswelldefinedandconsistentmulticastforwardingbehaviorintheCM.•SimplifiestheCMsinceprotocolspecificknowledgefortechnologiessuchasASMandSSMforI

2、Pv4andIPv6,includingtheprotocolsIGMPv3andMLDv2,isnolongerrequired.•EasiertoincorporatemulticastprotocolchangessincetheyonlyaffecttheCMTSandnottheCMs.•OthermulticastprotocolslikePIMcanbesupportedinthefuturebyutilizingthesameCMTStoCMsignalingwithoutaffectingtheCMs.•Itis

3、easiertosolveissuesrelatedtoMAClevelaliasing,accessandadmissioncontrolfromtheCMTS.2.MDF高层功能2.1CMTS用DSID标识组播报文a.CM通告CMTS加入组播组时会携带接口信息，CMTS在通告CMDSID组播转发绑定关系时会携带CM端口信息下来。b.非知名IPv6组播节目:不同的SSM(S,G)或ASM(*,G)在1个MACDomain要分配不同的DSID.PacketswithaknownDSIDarereceivedbytheCMandfo

4、rwardedtothesetofinterfacesassociatedwiththeDSID.AroutingCMTSMUSTlabeltrafficfordifferent"IPmulticastSSMChannels"or"IPmulticastASMGroups"withdifferentDSIDs,withtheexceptionofwell-knownIPv6multicasttraffic(refertoAnnexA.1.2).Thus,withMulticastDSID-basedForwarding,eachr

5、eplicationofan(S,G)IPmulticastsessiontoaparticularDCSisassignedauniqueDSIDlabelwithinaMACDomain.AbridgingCMTSSHOULD支持区分SSM(S,G)的能力，如果不具备至少要能为不同的GroupAddress分配不同的DSID.c.为了使用2.0/3.0CM混合场景，通过1个组播流会分配多个DSID。参见Figure9-3的场景。1）在此场景下bondingCM也只能从1条DC上接受组播节目。2）1个组播流在同一个channel

6、内分发多次。1个DSID是给nonbondingCM用的，另1个DSID是给bondingCM用的。这个应用下有一个问题，即2.0CM也会受到bondingDSID的同一个组播流的部分流量，但2.0的CM是不看DSID的，怎么办？answer:IsolationPacketPDUMACHeaderTheCMTSMUSTisolatebondedmulticasttrafficfromnon-bondedreplicationonthesamedownstreamchannelbytransmittingthesebondedmul

7、ticastpacketswiththeIsolationPacketPDUMACHeader(theFC_TypefieldoftheDOCSISframesettobinary10).BecausetheCMTSdoesnotknowoftheCM'scapabilitiesuntiltheCMregisters,theCMTSMUSTNOTisolatepre-registrationIPv6multicasttraffic(Section9.2.2.2)withtheIsolationPacketPDUMACHeader(

8、FC_Type10).DSIDlabelingenablesdifferentiationofmultiplereplicationsofanIPMulticastSession(bondedornon-bonded)ondownstreamcha