RFC 3376 IGMP v3.docx

RFC 3376 IGMP v3.docx

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RFC3376IGMPv3

NetworkWorkingGroupB.Cain

RequestforComments:

3376CerevaNetworks

Obsoletes:

2236S.Deering

Category:

StandardsTrackI.Kouvelas

CiscoSystems

B.Fenner

AT&TLabs-Research

A.Thyagarajan

Ericsson

October2002

InternetGroupManagementProtocol,Version3

StatusofthisMemo

ThisdocumentspecifiesanInternetstandardstrackprotocolforthe

Internetcommunity,andrequestsdiscussionandsuggestionsfor

improvements.Pleaserefertothecurrenteditionofthe"Internet

OfficialProtocolStandards"（STD1）forthestandardizationstate

andstatusofthisprotocol.Distributionofthismemoisunlimited.

CopyrightNotice

Copyright（C）TheInternetSociety（2002）.AllRightsReserved.

Abstract

ThisdocumentspecifiesVersion3oftheInternetGroupManagement

Protocol,IGMPv3.IGMPistheprotocolusedbyIPv4systemsto

reporttheirIPmulticastgroupmembershipstoneighboringmulticast

routers.Version3ofIGMPaddssupportfor"sourcefiltering",that

is,theabilityforasystemtoreportinterestinreceivingpackets

*only*fromspecificsourceaddresses,orfrom*allbut*specific

sourceaddresses,senttoaparticularmulticastaddress.That

informationmaybeusedbymulticastroutingprotocolstoavoid

deliveringmulticastpacketsfromspecificsourcestonetworkswhere

therearenointerestedreceivers.

ThisdocumentobsoletesRFC2236.

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RFC3376IGMPv3October2002

TableofContents

1.Introduction.........................2

2.TheServiceInterfaceforRequestingIPMulticastReception.3

3.MulticastReceptionStateMaintainedbySystems.......5

4.MessageFormats.......................7

5.DescriptionoftheProtocolforGroupMembers........19

6.DescriptionoftheProtocolforMulticastRouters......24

7.InteroperationwithOlderVersionsofIGMP..........35

8.ListofTimers,Counters,andTheirDefaultValues......40

9.SecurityConsiderations...................43

10.IANAConsiderations.....................47

11.Acknowledgments.......................47

12.NormativeReferences.....................47

13.InformativeReferences....................47

AppendixA.DesignRationale.................49

AppendixB.SummaryofchangesfromIGMPv2..........50

Authors'Addresses......................52

FullCopyrightStatement...................53

1.Introduction

TheInternetGroupManagementProtocol（IGMP）isusedbyIPv4systems

（hostsandrouters）toreporttheirIPmulticastgroupmembershipsto

anyneighboringmulticastrouters.NotethatanIPmulticastrouter

mayitselfbeamemberofoneormoremulticastgroups,inwhichcase

itperformsboththe"multicastrouterpart"oftheprotocol（to

collectthemembershipinformationneededbyitsmulticastrouting

protocol）andthe"groupmemberpart"oftheprotocol（toinform

itselfandother,neighboringmulticastroutersofitsmemberships）.

IGMPisalsousedforotherIPmulticastmanagementfunctions,using

messagetypesotherthanthoseusedforgroupmembershipreporting.

Thisdocumentspecifiesonlythegroupmembershipreportingfunctions

andmessages.

ThisdocumentspecifiesVersion3ofIGMP.Version1,specifiedin

[RFC-1112],wasthefirstwidely-deployedversionandthefirst

versiontobecomeanInternetStandard.Version2,specifiedin

[RFC-2236],addedsupportfor"lowleavelatency",thatis,a

reductioninthetimeittakesforamulticastroutertolearnthat

therearenolongeranymembersofaparticulargrouppresentonan

attachednetwork.Version3addssupportfor"sourcefiltering",

thatis,theabilityforasystemtoreportinterestinreceiving

packets*only*fromspecificsourceaddresses,asrequiredtosupport

Source-SpecificMulticast[SSM],orfrom*allbut*specificsource

addresses,senttoaparticularmulticastaddress.Version3is

designedtobeinteroperablewithVersions1and2.

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RFC3376IGMPv3October2002

MulticastListenerDiscovery（MLD）isusedinasimilarwaybyIPv6

systems.MLDversion1[MLD]implementsthefunctionalityofIGMP

version2;MLDversion2[MLDv2]implementsthefunctionalityofIGMP

version3.

Thecapitalizedkeywords"MUST","MUSTNOT","REQUIRED","SHALL",

"SHALLNOT","SHOULD","SHOULDNOT","RECOMMENDED","MAY",and

"OPTIONAL"inthisdocumentaretobeinterpretedasdescribedin

[RFC-2119].Duetothelackofitalics,emphasisisindicatedherein

bybracketingawordorphrasein"*"characters.

2.TheServiceInterfaceforRequestingIPMulticastReception

WithinanIPsystem,thereis（atleastconceptually）aservice

interfaceusedbyupper-layerprotocolsorapplicationprogramsto

asktheIPlayertoenableanddisablereceptionofpacketssentto

specificIPmulticastaddresses.Inordertotakefulladvantageof

thecapabilitiesofIGMPv3,asystem'sIPserviceinterfacemust

supportthefollowingoperation:

IPMulticastListen（socket,interface,multicast-address,

filter-mode,source-list）

where:

o"socket"isanimplementation-specificparameterusedto

distinguishamongdifferentrequestingentities（e.g.,programsor

processes）withinthesystem;thesocketparameterofBSDUnix

systemcallsisaspecificexample.

o"interface"isalocalidentifierofthenetworkinterfaceonwhich

receptionofthespecifiedmulticastaddressistobeenabledor

disabled.Interfacesmaybephysical（e.g.,anEthernetinterface）

orvirtual（e.g.,theendpointofaFrameRelayvirtualcircuitor

theendpointofanIP-in-IP"tunnel"）.Animplementationmayallow

aspecial"unspecified"valuetobepassedastheinterface

parameter,inwhichcasetherequestwouldapplytothe"primary"

or"default"interfaceofthesystem（perhapsestablishedbysystem

configuration）.Ifreceptionofthesamemulticastaddressis

desiredonmorethanoneinterface,IPMulticastListenisinvoked

separatelyforeachdesiredinterface.

o"multicast-address"istheIPmulticastaddress,orgroup,towhich

therequestpertains.Ifreceptionofmorethanonemulticast

addressonagiveninterfaceisdesired,IPMulticastListenis

invokedseparatelyforeachdesiredmulticastaddress.

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RFC3376IGMPv3October2002

o"filter-mode"maybeeitherINCLUDEorEXCLUDE.InINCLUDEmode,

receptionofpacketssenttothespecifiedmulticastaddressis

requested*only*fromthoseIPsourceaddresseslistedinthe

source-listparameter.InEXCLUDEmode,receptionofpacketssent

tothegivenmulticastaddressisrequestedfromallIPsource

addresses*except*thoselistedinthesource-listparameter.

o"source-list"isanunorderedlistofzeroormoreIPunicast

addressesfromwhichmulticastreceptionisdesiredornotdesired,

dependingonthefiltermode.AnimplementationMAYimposealimit

onthesizeofsourcelists,butthatlimitMUSTNOTbelessthan

64addressesperlist.Whenanoperationcausesthesourcelist

sizelimittobeexceeded,theserviceinterfaceMUSTreturnan

error.

Foragivencombinationofsocket,interface,andmulticastaddress,

onlyasinglefiltermodeandsourcelistcanbeineffectatanyone

time.However,eitherthefiltermodeorthesourcelist,orboth,

maybechangedbysubsequentIPMulticastListenrequeststhatspecify

thesamesocket,interface,andmulticastaddress.Eachsubsequent

requestcompletelyreplacesanyearlierrequestforthegivensocket,

interfaceandmulticastaddress.

PreviousversionsofIGMPdidnotsupportsourcefiltersandhada

simplerserviceinterfaceconsistingofJoinandLeaveoperationsto

enableanddisablereceptionofagivenmulticastaddress（from*all*

sources）onagiveninterface.Theequivalentoperationsinthenew

serviceinterfacefollow:

TheJoinoperationisequivalentto

IPMulticastListen（socket,interface,multicast-address,

EXCLUDE,{}）

andtheLeaveoperationisequivalentto:

IPMulticastListen（socket,interface,multicast-address,

INCLUDE,{}）

where{}isanemptysourcelist.

AnexampleofanAPIprovidingthecapabilitiesoutlinedinthis

serviceinterfaceisin[FILTER-API].

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RFC3376IGMPv3October2002

3.MulticastReceptionStateMaintainedbySystems

3.1.SocketState

ForeachsocketonwhichIPMulticastListenhasbeeninvoked,the

systemrecordsthedesiredmulticastreceptionstateforthatsocket.

Thatstateconceptuallyconsistsofasetofrecordsoftheform:

（interface,multicast-address,filter-mode,source-list）

Thesocketstateevolvesinresponsetoeachinvocationof

IPMulticastListenonthesocket,asfollows:

oIftherequestedfiltermodeisINCLUDE*and*therequestedsource

listisempty,thentheentrycorrespondingtotherequested

interfaceandmulticastaddressisdeletedifpresent.Ifnosuch

entryispresent,therequestisignored.

oIftherequestedfiltermodeisEXCLUDE*or*therequestedsource

listisnon-empty,thentheentrycorrespondingtotherequested

interfaceandmulticastaddress,ifpresent,ischangedtocontain

therequestedfiltermodeandsourcelist.Ifnosuchentryis

present,anewentryiscreated,usingtheparametersspecifiedin

therequest.

3.2.InterfaceState

Inadditiontotheper-socketmulticastreceptionstate,asystem

mustalsomaintainorcomputemulticastrece