rfc3376

NetworkWorkingGroupB.CainRequestforComments:3376CerevaNetworksObsoletes:2236S.DeeringCategory:StandardsTrackI.KouvelasCiscoSystemsB.FennerAT&TLabs-ResearchA.ThyagarajanEricssonOctober2002InternetGroupManagementProtocol,Version3StatusofthisMemoThisdocumentspecifiesanInternetstandardstrackprotocolfortheInternetcommunity,andrequestsdiscussionandsuggestionsforimprovements.PleaserefertothecurrenteditionoftheInternetOfficialProtocolStandards(STD1)forthestandardizationstateandstatusofthisprotocol.Distributionofthismemoisunlimited.CopyrightNoticeCopyright(C)TheInternetSociety(2002).AllRightsReserved.AbstractThisdocumentspecifiesVersion3oftheInternetGroupManagementProtocol,IGMPv3.IGMPistheprotocolusedbyIPv4systemstoreporttheirIPmulticastgroupmembershipstoneighboringmulticastrouters.Version3ofIGMPaddssupportforsourcefiltering,thatis,theabilityforasystemtoreportinterestinreceivingpackets*only*fromspecificsourceaddresses,orfrom*allbut*specificsourceaddresses,senttoaparticularmulticastaddress.Thatinformationmaybeusedbymulticastroutingprotocolstoavoiddeliveringmulticastpacketsfromspecificsourcestonetworkswheretherearenointerestedreceivers.ThisdocumentobsoletesRFC2236.Cain,et.al.StandardsTrack[Page1]RFC3376IGMPv3October2002TableofContents1.Introduction.........................22.TheServiceInterfaceforRequestingIPMulticastReception.33.MulticastReceptionStateMaintainedbySystems.......54.MessageFormats.......................75.DescriptionoftheProtocolforGroupMembers........196.DescriptionoftheProtocolforMulticastRouters......247.InteroperationwithOlderVersionsofIGMP..........358.ListofTimers,Counters,andTheirDefaultValues......409.SecurityConsiderations...................4310.IANAConsiderations.....................4711.Acknowledgments.......................4712.NormativeReferences.....................4713.InformativeReferences....................47AppendixA.DesignRationale.................49AppendixB.SummaryofchangesfromIGMPv2..........50Authors’Addresses......................52FullCopyrightStatement...................531.IntroductionTheInternetGroupManagementProtocol(IGMP)isusedbyIPv4systems(hostsandrouters)toreporttheirIPmulticastgroupmembershipstoanyneighboringmulticastrouters.NotethatanIPmulticastroutermayitselfbeamemberofoneormoremulticastgroups,inwhichcaseitperformsboththemulticastrouterpartoftheprotocol(tocollectthemembershipinformationneededbyitsmulticastroutingprotocol)andthegroupmemberpartoftheprotocol(toinformitselfandother,neighboringmulticastroutersofitsmemberships).IGMPisalsousedforotherIPmulticastmanagementfunctions,usingmessagetypesotherthanthoseusedforgroupmembershipreporting.Thisdocumentspecifiesonlythegroupmembershipreportingfunctionsandmessages.ThisdocumentspecifiesVersion3ofIGMP.Version1,specifiedin[RFC-1112],wasthefirstwidely-deployedversionandthefirstversiontobecomeanInternetStandard.Version2,specifiedin[RFC-2236],addedsupportforlowleavelatency,thatis,areductioninthetimeittakesforamulticastroutertolearnthattherearenolongeranymembersofaparticulargrouppresentonanattachednetwork.Version3addssupportforsourcefiltering,thatis,theabilityforasystemtoreportinterestinreceivingpackets*only*fromspecificsourceaddresses,asrequiredtosupportSource-SpecificMulticast[SSM],orfrom*allbut*specificsourceaddresses,senttoaparticularmulticastaddress.Version3isdesignedtobeinteroperablewithVersions1and2.Cain,et.al.StandardsTrack[Page2]RFC3376IGMPv3October2002MulticastListenerDiscovery(MLD)isusedinasimilarwaybyIPv6systems.MLDversion1[MLD]implementsthefunctionalityofIGMPversion2;MLDversion2[MLDv2]implementsthefunctionalityofIGMPversion3.ThecapitalizedkeywordsMUST,MUSTNOT,REQUIRED,SHALL,SHALLNOT,SHOULD,SHOULDNOT,RECOMMENDED,MAY,andOPTIONALinthisdocumentaretobeinterpretedasdescribedin[RFC-2119].Duetothelackofitalics,emphasisisindicatedhereinbybracketingawordorphrasein*characters.2.TheServiceInterfaceforRequestingIPMulticastReceptionWithinanIPsystem,thereis(atleastconceptually)aserviceinterfaceusedbyupper-layerprotocolsorapplicationprogramstoasktheIPlayertoenableanddisablereceptionofpacketssenttospecificIPmulticastaddresses.InordertotakefulladvantageofthecapabilitiesofIGMPv3,asystem’sIPserviceinterfacemustsupportthefollowingoperation:IPMulticastListen(socket,interface,multicast-address,filter-mode,source-list)where:osocketisanimplementation-specificparameterusedtodistinguishamongdifferentrequestingentities(e.g.,programsorprocesses)withinthesystem;thesocketparameterofBSDUnixsystemcallsisaspecificexample.ointerfaceisalocalidentifierofthenetworkinterfaceonwhichreceptionofthespecifiedmulticastaddressistobeenabledordisabled.Interfacesmaybephysical(e.g.,anEthernetinterface)orvirtual(e.g.,theendpointofaFrameRelayvirtualcircuitortheendpointofanIP-in-IPtunnel).Animplementationmayallowaspecialunspecifiedvaluetobepassedastheinterfaceparameter,inwhichcasetherequestwouldapplytotheprimaryordefaultinterfaceofthesystem(perhapsestablishedbysystemconfiguration).Ifreceptionofthesamemulticastaddressisdesiredonmorethanoneinterface,IPMulticastListenisinvo