第12章多播路由协议

[e-mail]1Chapter12MulticastingandMulticastRoutingProtocolsIntroductionMulticastaddressesandIGMPMulticastroutingMulticastroutingprotocol[e-mail]212.1IntroductionIPUnicasting，IP单播通信OnesourceOnedestinationintheInternetunicastunicastaddressaddressIPMulticasting，IP多播通信OnesourceAgroupofdestinationsintheInternetunicastmulticastaddressaddressIPBroadcasting，IP广播通信Onesource[e-mail]3DataLinkLayerPhysicalmulticastsupportMostLANssupportphysicalmulticastaddressingMappingIPmulticastaddressestophysicalmulticastaddressesNophysicalmulticastsupportMostWANsDONOTsupportphysicalmulticastaddressingUsingtunneling（隧道技术）toencapsulatethemulticastIPpacketinaunicastIPpacket[e-mail]•Lessbandwidth•Lessloadofsource•[e-mail]5MulticastApplicationsAccesstodistributeddatabase访问分布式数据库Informationdissemination信息传播DisseminationofNews传播新闻Teleconferencing电视会议Distancelearning远程学习[e-mail]612.2MulticastAddressandIGMPMulticastaddressFunction:defineahostgroupIPmulticastaddressesMACmulticastaddressesMappingclassDtoEthernetMACaddressIGMPInternetGroupManagementProtocol网际组管理协议[e-mail]712.2.1IPMulticastAddressAllocation:IANA（RFC3171）ClassD:224.0.0.0～239.255.255.255LocalNetworkControlBlock224.0.0.0/24:224.0.0.0～224.0.0.255NotbeforwardedbyrouterInternetworkControlBlock224.0.1.0/24:224.0.1.0～224.0.1.255MustbeforwardedthroughtheInternetAdministrativelyScopedAddressBlock239.0.0.0/8:239.0.0.0～239.255.255.255类似于私有IP单播地址（如10.0.0.0/8）[e-mail]812.2.2MACMulticastAddressIEEEMACaddressformatStandardGroupMACAddressesAllocation:IEEERegistrationAuthorityIEEE802.1DMACBridgeFilteredMACGroupAddresses01-80-C2-00-00-00～01-80-C2-00-00-0FStandardMACGroupAddresses01-80-C2-00-00-10～01-80-C2-FF-FF-FFOthers－IP-mappedEthernetMACgroupaddresses01-00-5E-[e-mail]912.2.3MappingClassDtoEthernetMACAddressExampleProblem:不明确的MAC地址IP多播地址:MAC多播地址＝25:1＝32:1例:0x0100.5E01.0101表示32个IP多播地址224.1.1.1,224.128.1.1,225.1.1.1,225.128.1.1,…239.128.1.1239.255.0.101-00-5E-7F-00-011110MulticastID:28bitsLost5bitsPrefix:25bitsMulticastID:[e-mail]1012.2.4IGMPInternetGroupManagementProtocol网际组管理协议Version1:RFC1112Version2:RFC2236Version3:RFC3376,RFC4604FunctionUsedbetweenhostsandmulticastroutersonasinglephysicalnetworkHelpthemulticastrouterscreateandupdatealistofloyalmembersrelatedtoeachrouterinterfaceNotamulticastroutingprotocol,butinc[e-mail]11IGMPOperationIGMPoperateslocallyJoiningagroupLeavingagroup[e-mail]1212.3MulticastRoutingObjectivesofmulticastingOptimalrouting[e-mail]1312.3.1ObjectivesofMulticastingEverymemberofthegroupshouldreceiveone,andonlyonecopyofthemulticastpacketNonmembersmustnotreceiveacopyTheremustbenoloopsinrouting,thatis,apacketmustnotvisitaroutermorethanonce[e-mail]1412.3.2OptimalRouting:ShortestPathTreesShortestpathtreeinunicastroutingEachrouterhasaroutingtablethatdefinesashortestpathtopossibledestinationsRoot:eachrouteritselfLeaf:possibledestinationsShortestpathtreeinmulticastroutingEachinvolvedrouterneedstoconstructashortestpathtreeforeachgroupTwotypesoftrees:source-based,[e-mail][e-mail]16Flooding，洪泛FloodingisrelatedtobothmulticastingandbroadcastingMethodForwardsapacketoutofallofitsinterfacesexcepttheonefromwhichthepacketcameFeatureProvidebroadcastingCreateloopsandtrafficjams:[e-mail]17ShortestPathTreeinMulticastRoutingSource-BasedTree源点基准树or有源树EachcombinationofsourceandgrouphasasingletreeEx.:NgroupsandMsourcesNxMtreesNotation:(S,G)——S＝多播源IP地址，G＝多播组地址Group-SharedTree组共享树or共享树EachgroupsharesthesametreeSteinertree,rendezvous-pointtree（汇集点树，RPT）Ex.:NgroupsNtreesNotation:(*,G)——*＝所有的多播源，G＝多播组地址[e-mail]18Source-BasedTree主机A主机B主机CR1R2R4R6192.1.1.1192.2.2.2192.3.3.3假设：A、B、C在多播组224.1.1.1中R1R5R3ABC(192.1.1.1,224.1.1.1)R5R3R1BCA(192.1.1.2,224.1.1.1)[e-mail]19Discuss:(S,G)（S,G）：最短路径树（SPT）树根：多播组G的信息源（S）在具体的多播路由协议中，S通常指源子网树叶：多播组G的接收成员（S,G）是单向树多播信息流只能沿树的下行方向传播典型的多播路由协议DVMRP：单播D-V路由选择的扩展MOSPF：单播L-S路由选择的扩展PIM-DM：根据需要使用单播路由选择协议[e-mail]20Group-SharedTree:RPT主机A主机B主机CR1R2R4R6192.1.1.1192.2.2.2192.3.3.3R3R5主机D192.4.4.4根主机E192.5.5.5(*,224.2.2.2)R5R2R4CR6R3BD假设：A、B、C、D、E在多播组224.2.2.2中[e-mail]21BidirectionalRPT主机A主机B主机CR1R2R4R6192.1.1.1192.2.2.2192.3.3.3假设：A、B、C、D、E在多播组224.2.2.2中R3R5主机D192.4.4.4(*,224.2.2.2)R5R2R1R4CAR6R3EB根主机E192.5.5.5D上行下行[e-mail]22UnidirectionalRPT主机A主机B主机CR1R2R4R6192.1.1.1192.2.2.219