Network Protocols IP Multicast TDC375 Winter 2002 John Kristoff DePaul University 1 Recall Unicast Broadcast Multicast Unicast sender address Send to received by specific IP address group TDC375 Winter 2002 John Kristoff DePaul University 1 Unicast one to many TDC375 Winter 2002 John Kristoff DePaul University 1 Multicast one to many TDC375 Winter 2002 John Kristoff DePaul University 1 Multicast operation overview Class D destination address space 224 0 0 0 4 First bits of first octet must be 1110 How do multicast groups become known How do receivers join leave multicast group How to get multicast data to all receivers How to map IP destination to MAC address TDC375 Winter 2002 John Kristoff DePaul University 1 IP multicast addressing Reserved assigned addresses 224 0 0 0 24 link local 239 0 0 0 8 administratively scoped Etc see IANA multicast address assignments IP to Ethernet MAC mapping Take IP destination low order 23 bits Put into Ethernet destination low order 23 bits Well known Ethernet OUI 01 00 5e TDC375 Winter 2002 John Kristoff DePaul University 1 Internet group multicast protocol IGMP Host router membership signalling protocol Hosts use IGMP to join leave groups Routers use IGMP to build forwarding state IGMPv1 1st generation host router protocol IGMPv2 hosts use explicit leave messages IGMPv3 hosts selectively filter sources TDC375 Winter 2002 John Kristoff DePaul University 1 IGMP packet formats TDC375 Winter 2002 John Kristoff DePaul University 1 IP multicast routing Broadcast and prune DVMRP PIM DM Reverse shortest path tree Routers do reverse path forwarding RPF check Explicit join CBT PIM SM Receivers send join to a rendevous point RP Senders send multicast data to RP up the tree RP fans out multicast data its a meeting point Optimizations in PIM SM short cut the RP TDC375 Winter 2002 John Kristoff DePaul University 1 Distance vector multicast routing protocol DVMRP Similar to RIP Infinity 32 hops Flood throughout prune back if necessary Graft back leafs if necessary requires state 1st generation MBONE protocol deprecated Scales poorly PIM DM is similar OK for dense population TDC375 Winter 2002 John Kristoff DePaul University 1 Protocol independent multicast sparse mode PIM SM Underlying unicast forwarding info is used Receivers must explicitly join groups Everyone meets at rendezvous point RP RP is the core of a unidirectional tree Senders encapsulate multicast data to RP RP can forward join or de register Optimization allows short cuts around RP Also has some scaling and RP reliance probs TDC375 Winter 2002 John Kristoff DePaul University 1 PIM SM illustrated TDC375 Winter 2002 John Kristoff DePaul University 1 Multiprotocol BGP Extensions to BGP to carry other routes e g Multicast Can provide aggregation routing policy etc Used between autonomous system AS domains Carries information about sources of multicast TDC375 Winter 2002 John Kristoff DePaul University 1 Multicast source discovery protocol MDSP Typically an RP is deployed per AS RPs must know about Internet wide sources MSDP sends session announcements SAs MSDP TCP sessions between RPs peers MSDP messages are flooded to all RPs TDC375 Winter 2002 John Kristoff DePaul University 1 Internet IP multicast From DVMRP MBONE to today Some deployment mostly Internet2 PIM SM MBGP MSDP used today Single source multicast SSM coming Security and denial of service attack issues Common tools and apps IP TV sdr mtrace etc TDC375 Winter 2002 John Kristoff DePaul University 1
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