TCPIP协议原理ChapterIP组播.pptx

《TCPIP协议原理ChapterIP组播.pptx》由会员分享，可在线阅读，更多相关《TCPIP协议原理ChapterIP组播.pptx（61页珍藏版）》请在淘文阁 - 分享文档赚钱的网站上搜索。

1、单播、广播与组播单播、广播与组播单播组播广播第1页/共61页实现点对多点通信的两种途径(1)多个单播：发送者对每个接收者都采用一条单播传输；共有 90 个主机接收视频节目R1R3R4R2视频服务器 M30 个30 个90 个30 个30 个30 个30个第2页/共61页实现点对多点通信的两种途径(2)组播发送主机仅发送一个包；一旦该包需要转发，路由器才进行复制；组播组成员共有 90 个R1R3R4R2视频服务器 M组播1 个组播1 个1 个1 个1 个组播1 个1 个发送 1 次组播复制第3页/共61页IP Multicast How Does it Work?The sender(sourc

2、e)sends one copy of a single packet addressed to a group of receivers-multicast groupMulticast routers replicate and forward the packet to all the branches where receivers(may)existReceivers express（表达了）their interest in multicast traffic by sending control messages to routers第4页/共61页Why Multicast?m

3、ore and more multimedia communication application and service have emerged in Internet that all the recipients want the same type of dataEx.Digital TV,Digital Radio,Video ConferenceConsume much more bandwidth than usual applicationRequire high QoS supportBelong to one-to-many communication style第5页/

4、共61页Enhanced EfficiencyOptimized PerformanceDistributed ApplicationsExample:Audio StreamingAll clients listening to the same 8-Kbps audio00.20.40.60.8TrafficMbps120406080100Number of ClientsMulticastUnicastMulticast Advantages第6页/共61页组播应用一对多定时的媒体播放，“推送”服务（股票价格，天气预报）；多对多网络游戏，视频会议有反馈的多对一资源发现，数据收集第7页/共

5、61页IP Multicast ApplicationsCorporate BroadcastsDistance LearningTrainingVideo ConferencingWhiteboard/CollaborationMulticast File TransferData and File ReplicationReal-Time Data DeliveryFinancialVideo-On-DemandLive TV and Radio Broadcast to the Desktop第8页/共61页组播通信的几个问题如何标识组播通信的接收方？如何确定和维护组成员关系？如何为发送

6、给这些接收者的数据报寻址？IP组播编址机制组播编址机制组成员关系协议组成员关系协议组播路由协议组播路由协议组组播播体体系系结结构构第9页/共61页组播组和组播地址IP组播地址由D类IP地址标记。地址的最高四位为“1110”；范围224.0.0.0239.255.255.255。D类IP地址又进行了划分。224.0.0.255238.255.255.255239.255.255.255224.0.0.0本地管理组播地址用户组播地址保留组播地址第10页/共61页组播组和组播地址从224.0.0.0至224.0.0.255的地址被IANA保留为网络协议使用，作为永久组的地址，其中比较重要的地址有：2

7、24.0.0.1 网段上所有支持组播的主机224.0.0.2 网段上所有支持组播的路由器224.0.0.4 所有DVMRP路由器224.0.0.5 所有OSPF路由器224.0.0.6 指定的OSPF路由器224.0.0.9 所有RIP2路由器224.0.0.10 所有IGRP路由器224.0.0.13 所有PIM路由器第11页/共61页D类IP地址与以太网多播地址的映射关系 0000000000000001010111100111008162431D 类类 IP 地址地址这 5 位不使用48 位以太网地址0 1 0 0 5 E表示多播最低 23 位来自 D 类 IP 地址第12页/共61页组

8、播协议组成员关系协议主机-路由器之间；主要有IGMP，它负责建立并维护路由器直联网段的组成员关系信息。组播路由协议路由器-路由器之间；根据IGMP维护的这些组播组成员关系信息，运用一定的组播路由算法构造组播分布树进行组播分组转发，主要包括DVMRP、MOSPF、CBT、PIM-DM、PIM-SM等。第13页/共61页Internet组管理协议(IGMP)目前已使用的有3个版本：IGMPv1，v2和v3。它用于将局域网内主机的组成员关系报告给本网段内的组播路由器。第14页/共61页Internet组管理协议(IGMP)IGMP只工作在本地范围。128.56.24.34135.27.74.5213

9、0.12.14.56130.12.14.43组播组226.15.37.123IGMPIGMPIGMPIGMPR1R4R3R2第15页/共61页Internet组管理协议(IGMP)第16页/共61页IGMP工作的两个阶段(1)当某个主机加入新的组播组时，该主机应向组播组的组播路由器发送IGMP 报文，声明自己要成为该组的成员。本地的组播路由器收到 IGMP 报文后，将组成员关系转发给因特网上的其他组播路由器。第17页/共61页IGMP工作的两个阶段(2)因为组成员关系是动态的，因此本地组播路由器要周期性地探询本网上的主机，以便知道这些主机是否还继续是组成员。只要对某个组有一个主机响应，那么组播

10、路由器就认为这个组是活跃的。但一个组在经过几次的探询后仍然没有一个主机响应，则不再将该组的成员关系转发给其他的组播路由器。第18页/共61页IGMP报文格式与类型报文格式v报文类型：查询，成员报告，退出报告。第19页/共61页IGMP报文的封装IGMP报文封装在IP数据报中发送。IP报头：协议字段值=2TTL=1（因为IGMP只在本地工作）目的IP地址：第20页/共61页H2Joining member sends report to 224.1.1.1 immediately upon joining(same as IGMPv1)H2224.1.1.1Report1.1.1.1H1H31.

11、1.1.101.1.1.111.1.1.12rtr-aIGMPv2Joining a Group第21页/共61页Router sends periodic queriesOne member per group per subnet reportsOther members suppress reportsQuery1.1.1.1IGMPv21.1.1.101.1.1.111.1.1.12224.1.1.1Report224.1.1.1SuppressedX224.1.1.1SuppressedXH1H2H3IGMPv2Maintaining a Group第22页/共61页IGMPv21.

12、1.1.11.1.1.2H1H2H31.1.1.101.1.1.111.1.1.12Initially,all routers send out a queryQueryQueryRouter with the lowest IP address is elected querierIGMPQuerierOther routers become non-queriersIGMPNon-Querierrtr-artr-bIGMPv2Querier Election第23页/共61页H2 leaves group;sends Leave messageLeave to224.0.0.2224.1.

13、1.1#1#1Router sends Group-Specific QueryGroup-SpecificQuery to 224.1.1.1#2#2A remaining member host sends reportReport to224.1.1.1224.1.1.1#3#3Group remains activeH11.1.1.101.1.1.1rtr-aH31.1.1.121.1.1.11H2H2IGMPv2Leaving a Group第24页/共61页Last host leaves group;sends Leave messageLeave to224.0.0.2224.

14、1.1.1#1#1Router sends Group-Specific QueryGroup-SpecificQuery to 224.1.1.1#2#2No report is receivedGroup times outH21.1.1.1rtr-aH11.1.1.101.1.1.121.1.1.11H3H3IGMPv2Leaving a Group第25页/共61页组播与单播在选路的不同组播转发必须动态地适应组播组成员的变化（这时网络拓扑并未发生变化）。请注意，单播路由选择通常是在网络拓扑发生变化时才需要更新路由。组播数据报可以由没有加入组播组的主机发出，也可以通过没有组成员接入的网络

15、。组播路由器在转发组播数据报时，不能仅仅根据组播数据报中的目的地址。在转发时，组播路由器使用数据报的源地址和目在转发时，组播路由器使用数据报的源地址和目的地址的地址第26页/共61页Multicast ForwardingMulticast routing works the opposite way of unicast routingUnicast routing is concerned with where the packet is goingMulticast routing is concerned with where the packet comes fromMulticas

16、t routing uses Reverse Path Forwarding(反向路径转发)to prevent forwarding loops第27页/共61页Reverse Path Forwarding(RPF)What is RPF?A router forwards a multicast datagram only if received on the upstream interface to the source,i.e.it follows the distribution treeThe RPF CheckThe routing table for unicast is

17、checked against the source address in the multicast datagramIf the datagram arrived on the interface specified in the routing table for the source address:The RPF check succeedsOtherwise,the RPF check fails第28页/共61页Reverse Path Forwarding(cont.)Reverse Path Forwarding(RPF)check:If the RPF check succ

18、eeds,the datagram is forwardedIf the RPF check fails,the datagram is typically silently discardedWhen a datagram is forwarded,it is sent out of each interface in the outgoing interface listThe packet is never sent back out of the RPF interface第29页/共61页RPF CheckingSource151.10.3.21Multicast Distribut

19、ion TreeExample:RPF CheckingMulticast PacketsRPF Checks fail Packets arrived on wrong interface.第30页/共61页RPF Check SucceedsRPF Check Succeeds!Unicast Route TableNetwork Interface151.10.0.0/16S1198.14.32.0/24S0204.1.16.0/24E0E0S1S0S2Multicast packet fromsource 151.10.3.21Packet arrived on right inter

20、face!S1Forward out of all outgoing interfaces.(i.e.down the distribution tree)RPF Check(cont.)第31页/共61页RPF Check Fails!RPF Check FailsPacket arrived on wrong interface!E0S1S0S2Multicast acket fromsource 151.10.3.21XDiscard packet!Unicast Route TableNetwork Interface151.10.0.0/16S1198.14.32.0/24S0204

21、.1.16.0/24E0S1RPF Check第32页/共61页RPF InterfaceReverse Path Forwarding(RPF)check is done with respect（关于）to the RPF interfaceThe interface that is closest to the source Determined from any unicast or dedicated（专用）multicast table(DVMRP,MBGP)Periodic（周期性）recheck of the RPF interface第33页/共61页组播路由协议组播路由协议

22、负责构建组播分组的传输路径。组播分布树（Distribution Tree）在传输组播分组时，指派路由器构造一个连接所有组播组成员的树。根据这个树，路由器得出转发分组的一条唯一路径。由于组播组成员可以动态地加入和退出，因此组播分布树也必须动态更新。第34页/共61页组播路由协议根据构造方法的不同，有两种最基本的组播分布树：源分布树和共享分布树。源分布树（Source Distribution Tree）以组播源为根节点构造到所有组播组成员路径都最短的生成树。也称为最短路径树（Shortest Path Tree，SPT）。第35页/共61页Shortest-Path or Source Dis

23、tribution TreeReceiver 1BEADFSource 1Notation:(S,G)S=Source G=GroupCReceiver 2Source 2Shortest-Path Trees第36页/共61页Shortest-Path or Source Distribution TreeReceiver 1BEADFSource 1Notation:(S,G)S=Source G=GroupCReceiver 2Source 2The Tree is per SOURCEShortest-Path Trees第37页/共61页Shortest-Path Trees在每一个

24、组播组内，每个源节点建立一棵到所有其它成员的最短路径树，即源节点和组的每一种组合构成一棵树。每一个路由器必须有关于每一个特定树的信息，路由器根据组播分组的源地址及组地址确定使用哪棵多播树转发。优点：多播分组总是使用最佳路径转发。缺点：路由器需要维护大量的多播树。第38页/共61页Shared Distribution Tree共享分布树（Shared Distribution Tree）以网络中的某一个指定的路由器为根节点，该路由器称为汇聚点（Rendezvous Point，RP）或核心，由此节点生成包含所有组成员的组播树。也称为RP树（RPT）或基于核心的树（Core-Based Tree

25、，CBT）。第39页/共61页Shared Distribution TreeReceiver 1BEADFNotation:(*,G)*=All Sources G=GroupCReceiver 2(RP)(RP)PIM Rendezvous PointShared TreeShared Distribution Tree第40页/共61页Shared Distribution TreeReceiver 1BEADFNotation:(*,G)*=All Sources G=GroupSource 1CReceiver 2Source 2Source Tree(RP)(RP)PIM Rend

26、ezvous PointShared TreeShared Distribution Tree第41页/共61页Shared Distribution Tree每个组播组使用一棵以核心路由器为根的组播树。优点：路由器对于每个组只要维护一棵组播树，内存消耗减少。缺点：组播分组使用的转发路径可能不是最佳的，这是组共享树为实现可扩展性而付出的性能代价。第42页/共61页组播路由协议组播路由协议的主要任务就是构造组播的分布树，使组播分组能够传送到相应的组播组成员。根据对网络中的组播成员的分布和使用的不同，组播路由协议分为两类：密集模式路由协议（DM）稀疏模式路由协议（SM）。第43页/共61页DM路由

27、协议DM路由协议通常用于组播组成员（接收者）密集地分布且有足够带宽的网络环境。DM路由协议采用一种定期广播组播组的扩散-剪枝技术来维护组播分布树，它只使用源分布树（SPT）。DM路由协议有：DVMRP（Distance Vector Multicast Routing Protocol，距离向量组播路由协议）MOSPF（Multicast Open Shortest Path First，组播OSPF协议）PIM-DM（Protocol Independent Multicast-Dense Mode，协议无关组播协议-密集模式）第44页/共61页PIM-Dense Mode(PIM-DM)P

28、rotocol independent supports all underlying（已有）unicast routing protocols:static,RIP,IGRP,EIGRP,IS-IS,OSPF,and BGPUses flood and prune mechanismFloods network and prunes back based on multicast group membershipAssert mechanism used to prune off redundant flows on multiaccess networksAppropriate for s

29、maller implementations and pilot networks（适用于小规模实验型网络）第45页/共61页Initial FloodingSourceReceiverMulticast Packets(S,G)state created inevery router in the network!PIM-DM Flood and Prune第46页/共61页Pruning Unwanted TrafficSourceReceiverMulticast PacketsPrune MessagesPIM-DM Flood and Prune(cont.)第47页/共61页Sou

30、rceResults after PruningReceiverMulticast PacketsFlood and Prune processrepeats every three minutes!(S,G)state still exists inevery router in the network!PIM-DM Flood and Prune(cont.)第48页/共61页SM路由协议在网络中稀疏分布组播组成员、网络也没有充足带宽的情况（如广域网环境）下可以使用SM路由协议。SM路由协议采用选择性的建立和维护分布树的方式，由空树开始，仅当成员显式的请求加入分布树才做出修改。SM路由协议

31、有：CBT：基于核心的分布树协议PIM-SM（Protocol Independent Multicast-Sparse Mode，协议无关组播协议-稀疏模式）第49页/共61页ReceiverRP(*,G)JoinShared Tree(*,G)State created onlyalong the Shared Tree.PIM-SM Shared Tree Join第50页/共61页ReceiverRP(S,G)JoinSourceShared Tree(S,G)Register(unicast)Source Tree(S,G)State created onlyalong the So

32、urce Tree.Traffic FlowPIM-SM Sender Registration第51页/共61页ReceiverRPSourceShared TreeSource TreeRP sends a Register-Stop back to the first-hop router to stop the Register process.(S,G)Register-Stop(unicast)Traffic Flow(S,G)Register(unicast)(S,G)traffic begins arriving at the RP via the Source tree.PI

33、M-SM Sender Registration(cont.)第52页/共61页ReceiverRPSourceShared TreeSource TreeTraffic FlowSource traffic flows nativelyalong SPT to RP.From RP,traffic flows downthe Shared Tree to Receivers.PIM-SM Sender Registration(cont.)第53页/共61页ReceiverRP(S,G)JoinSourceSource TreeShared TreeLast-hop router joins

34、 the Source Tree.Additional(S,G)State is created along new part of the Source Tree.Traffic FlowPIM-SM SPT Switchover第54页/共61页ReceiverRPSourceSource TreeShared Tree(S,G)RP-bit PruneTraffic begins flowing down the new branch of the Source Tree.Additional(S,G)State is created along along the Shared Tre

35、e to prune off(S,G)traffic.Traffic FlowPIM-SM SPT Switchover第55页/共61页ReceiverRPSourceSource TreeShared Tree(S,G)Traffic flow is now pruned off of the Shared Tree and is flowing to the Receiver via the Source Tree.Traffic FlowPIM-SM SPT Switchover(cont.)第56页/共61页ReceiverRPSourceSource TreeShared Tree

36、(S,G)traffic flow is no longer needed by the RP,so it Prunes the flow of(S,G)traffic.Traffic Flow(S,G)PrunePIM-SM SPT Switchover(cont.)第57页/共61页ReceiverRPSourceSource TreeShared Tree(S,G)Traffic flow is now only flowing to the Receiver via a single branch of the Source Tree.Traffic FlowPIM-SM SPT Switchover(cont.)第58页/共61页习题组播路由器的表中有4个组（W、X、Y和Z），局域网上有3台主机。主机A有3个属于组W的成员，有一个属于组X的成员。主机B有2个属于组W的成员，有1个属于组Y的成员。主机C没有属于任何组的进程。试给出处于监视状态的IGMP报文。第59页/共61页组播路由协议第60页/共61页谢谢您的观看！第61页/共61页