10internet组播-新.pptx

InternetInternet组播简介组播简介1清华大学 研究生课程为什么需要组播？组播地址主机和路由器的交互：IGMP 组播分发树组播转发域内组播路由协议域间组播路由协议IPv62清华大学 研究生课程主要内容主要内容为什么需要组播？组播地址主机和路由器的交互：IGMP 组播分发树组播转发域内组播路由协议域间组播路由协议IPv63清华大学 研究生课程主要内容主要内容清华大学 研究生课程4单播和组播的比较单播和组播的比较ServerRouterUnicastServerRouterMulticast Enhanced EfficiencyEnhanced Efficiency: Controls network traffic and reduces server and CPU loads Optimized PerformanceOptimized Performance: Eliminates traffic redundancy Distributed ApplicationsDistributed Applications: Makes multipoint applications possible5清华大学 研究生课程组播的优势组播的优势Example: Audio Streaming All clients listening to the same 8 Kbps audio00.20.40.60. 8Traffic Mbps120406080100 # ClientsMulticast UnicastBest Effort Delivery: Drops are to be expected. Multicast applications should not expect reliable delivery of data and should be designed accordingly. Reliable Multicast is still an area for much research No Congestion Avoidance: Lack of TCP windowing and “slow-start” mechanisms can result in network congestion. If possible, Multicast applications should attempt to detect and avoid congestion conditions6清华大学 研究生课程组播带来的问题组播带来的问题组播是基于UDP的！Duplicates: Some multicast protocol mechanisms (e.g. Asserts, Registers and SPT Transitions) result in the occasional generation of duplicate packetsOut of Order Delivery: Some protocol mechanisms may also result in out of order delivery of packets7清华大学 研究生课程组播带来的问题组播带来的问题MultimediaStreaming media, IPTVTraining, corporate communications Conferencing—video/audioNet GameAny one-to-many data push applications8清华大学 研究生课程组播的应用组播的应用为什么需要组播？组播地址主机和路由器的交互：IGMP 组播分发树组播转发域内组播路由协议域间组播路由协议IPv69清华大学 研究生课程主要内容主要内容清华大学 研究生课程10组播地址组播地址 IPv4 Multicast Group Addresses  224.0.0.0–239.255.255.255  Class “D” Address Space High order bits of 1st Octet = “1110”Reserved Link-local Addresses  224.0.0.0–224.0.0.255  Transmitted with TTL = 1  Examples:224.0.0.1 All systems on this subnet224.0.0.2 All routers on this subnet224.0.0.4 DVMRP routers224.0.0.5 OSPF routers224.0.0.13 PIMv2 routers清华大学 研究生课程11组播地址组播地址 Administratively Scoped Addresses239.0.0.0–239.255.255.255Private address spaceSimilar to RFC1918 unicast addressesNot used for global Internet trafficUsed to limit “scope” of multicast trafficSame addresses may be in use at different locations for different multicast sessionsExamplesSite-local scope: 239.253.0.0/16Organization-local scope: 239.192.0.0/14清华大学 研究生课程12组播地址组播地址32 Bits28 Bits25 Bits23 Bits48 Bits01-00-5e-7f-00-0111105 Bits LostIP Multicast MAC Address Mapping (FDDI and Ethernet)239.255.0.1清华大学 研究生课程13组播地址组播地址224.1.1.1 224.129.1.1 225.1.1.1 225.129.1.1... 238.1.1.1 238.129.1.1 239.1.1.1 239.129.1.10x0100.5E01.01011 - Multicast MAC Address (FDDI and Ethernet)32 - IP Multicast AddressesBe Aware of the 32:1 Address OverlapIP Multicast MAC Address Mapping (FDDI then the RPF checksucceeds • Otherwise, the RPF Check failsReverse Path Forwarding (RPF)清华大学 研究生课程43组播转发组播转发Source 151.10.3.21Example: RPF CheckingMcast PacketsRPF Check FailsRPF Check FailsPacket arrived on wrong interface! Packet arrived on wrong interface!清华大学 研究生课程44组播转发组播转发RPF Check Fails!Unicast Route Table Network Interface 151.10.0.0/16S1 198.14.32.0/24S0 204.1.16.0/24E0A closer look: RPF Check FailsPacket Arrived on Wrong Interface!E0S1S0S2S1S1Multicast Packet from Source 151.10.3.21XDiscard Packet!清华大学 研究生课程45组播转发组播转发A closer look: RPF Check SucceedsRPF Check SucceedsRPF Check Succeeds!Unicast Route TableUnicast Route Table NetworkNetwork Interface Interface 151.10.0.0/16151.10.0.0/16S1S1 198.14.32.0/24198.14.32.0/24S0S0 204.1.16.0/24204.1.16.0/24E0E0E0S1S0S2Multicast Packet from Source 151.10.3.21Packet Arrived on Correct Interface!S1S1 Forward out all outgoing interfaces. (i. e. down the distribution tree)为什么需要组播？组播地址主机和路由器的交互：IGMP 组播分发树组播转发域内组播路由协议域间组播路由协议IPv646清华大学 研究生课程主要内容主要内容Multicast Routing is not unicast routing You have to think of it differently It is not like OSPF It is not like RIP It is not like anything you may be familiar with47清华大学 研究生课程组组播播路由和单播路由路由和单播路由Dense-mode •Uses “Push” Model •Traffic Flooded throughout network •Pruned back where it is unwanted •Flood & Prune behavior (typically every 3 minutes) Sparse-mode •Uses “Pull” Model •Traffic sent only to where it is requested •Explicit Join behavior48清华大学 研究生课程组播路由协议的类型组播路由协议的类型Currently, there are four multicast routing protocolsDVMRPv3 (Internet-draft)DVMRPv1 (RFC 1075) is obsolete and unused. A variant is currently implementedMOSPF (RFC 1584)PIM-DM (Internet-draft)PIM-SM (RFC 2362- v2) Others (CBT, OCBT, QOSMIC, SM, etc.)49清华大学 研究生课程域内组播路由协议概况域内组播路由协议概况Dense Mode ProtocolDistance vector-basedSimilar to RIPInfinity = 32 hopsSubnet masks in route advertisementsDVMRP Routes usedFor RPF CheckTo build Truncated Broadcast Trees (TBTs)Uses special “Poison-Reverse” mechanism50清华大学 研究生课程DVMRPDVMRP概况概况Dense Mode ProtocolUses Flood and Prune operationTraffic initially flooded down TBT’sTBT。