【文章內(nèi)容簡介】 rrived on Correct Interface! Forward out all outgoing interfaces. (i. e. down the distribution tree) 38 169。 2022, Cisco Systems, Inc. 2214 1197_05_2022_c2 Agenda ? Why Multicast? ? Multicast Addressing ? HostRouter Signaling: IGMP ? Multicast Distribution Trees ? Multicast Forwarding ? Multicast Routing Protocols 39 169。 2022, Cisco Systems, Inc. 2214 1197_05_2022_c2 Multicast vs. Unicast Routing 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 with. 40 169。 2022, Cisco Systems, Inc. 2214 1197_05_2022_c2 Types of Multicast Protocols ?Densemode ? Uses ―Push‖ Model ? Traffic Flooded throughout work ? Pruned back where it is unwanted ? Flood amp。 Prune behavior (typically every 3 minutes) ?Sparsemode ? Uses ―Pull‖ Model ? Traffic sent only to where it is requested ? Explicit Join behavior 41 169。 2022, Cisco Systems, Inc. 2214 1197_05_2022_c2 Multicast Protocol Overview ?Currently, there are four multicast routing protocols: – DVMRPv3 (Interdraft) – DVMRPv1 (RFC 1075) is obsolete and unused. A variant is currently implemented – MOSPF (RFC 1584) – PIMDM (Interdraft) – PIMSM (RFC 2362 v2) – Others (CBT, OCBT, QOSMIC, SM, etc.) 42 169。 2022, Cisco Systems, Inc. 2214 1197_05_2022_c2 DVMRP Overview ?Dense Mode Protocol – Distance vectorbased ?Similar to RIP ?Infinity = 32 hops ?Sub masks in route advertisements – DVMRP Routes used: ?For RPF Check ?To build Truncated Broadcast Trees (TBTs) –Uses special ―PoisonReverse‖ mechanism – Uses Flood and Prune operation ?Traffic initially flooded down TBT’s ?TBT branches are pruned where traffic is unwanted. ?Prunes periodically timeout causing reflooding. 43 169。 2022, Cisco Systems, Inc. 2214 1197_05_2022_c2 DVMRP—Source Trees Route for source work of metric ―n‖ n m Source Network E X Y A B C D 2 34 Poison reverse (metric + infinity) sent to upstream ―parent‖ router. Router depends on ―parent‖ to receive traffic for this source. 2 2 33 33 1 1 1 35 35 ? Truncated Broadcast Trees Are Built using Best DVMRP Metrics Back to Source Network. ? Lowest IP Address Used in Case of a Tie. (Note: IP Address of D C B A) 3 3 mrouted mrouted mrouted mrouted mrouted Resulting Truncated Broadcast Tree for Source Network mrouted mrouted 44 169。 2022, Cisco Systems, Inc. 2214 1197_05_2022_c2 DVMRP—Source Trees Forwarding onto Multiaccess Networks Network X A B C 2 2 1 1 mrouted mrouted mrouted Route advertisement for work X of metric ―n‖ n ? Both B and C have routes to work X. ? To avoid duplicates, only one router can be ―Designated Forwarder‖ for work X. ? Router with best metric is elected as the ―Designated Forwarder‖. ? Lowest IP address used as tiebreaker. ? Router C wins in this example. (Note: IP Address of C B ) 45 169。 2022, Cisco Systems, Inc. 2214 1197_05_2022_c2 E X Y A B C D DVMRP—Source Trees Resulting Truncated Broadcast Tree for Source Network ―S1‖ Source Network ―S1‖ S1 Source Tree mrouted mrouted mrouted mrouted mrouted mrouted mrouted 46 169。 2022, Cisco Systems, Inc. 2214 1197_05_2022_c2 DVMRP—Source Trees Each Source Network has it’s Own Truncated Broadcast Tree E X Y A B C D Note: IP Address of D C B A S2 Source Tree Source ―S2‖ mrouted mrouted mrouted mrouted mrouted mrouted mrouted 47 169。 2022, Cisco Systems, Inc. 2214 1197_05_2022_c2 DVMRP—Flood amp。 Prune Source ―S‖ Receiver 1 (Group ―G‖) Truncated Broadcast Tree based on DVMRP route metrics (S, G) Multicast Packet Flow Initial Flooding of (S, G) Multicast Packets Down Truncated Broadcast Tree E X Y A B C D 1 mrouted mrouted mrouted mrouted mrouted mrouted mrouted 48 169。 2022, Cisco Systems, Inc. 2214 1197_05_2022_c2 DVMRP—Flood amp。 Prune Routers C is a Leaf Node so it sends an ―(S, G) Prune‖ Message Prune Source ―S‖ Receiver 1 (Group ―G‖) E X Y A B C D mrouted Router B Prunes interface. mrouted mrouted mrouted mrouted mrouted mrouted Truncated Broadcast Tree based on DVMRP route metrics (S, G) Multicast Packet Flow 49 169。 2022, Cisco Systems, Inc. 2214 1197_05_2022_c2 DVMRP—Flood amp。 Prune Routers X, and Y are also Leaf Nodes so they send ―Prune (S, G)‖ Messages Prune Prune Source ―S‖ Receiver 1 (Group ―G‖) E X Y A B C D mrouted mrouted mrouted mrouted mrouted mrouted Router E prunes interface. mrouted Truncated Broadcast Tree based on DVMRP route metrics (S, G) Multicast Packet Flow 50 169。 2022, Cisco Systems, Inc. 2214 1197_05_2022_c2 DVMRP—Flood amp。 Prune Router E is now a Leaf Node。 it sends an (S, G) Prune message. Prune Source ―S‖ Receiver 1 (Group ―G‖) E X Y A B C D mrouted mrouted mrouted mrouted mrouted mrouted Router D prunes interface. mrouted Truncated Broadcast Tree based on DVMRP route metrics (S, G) Multicast Packet Flow 51 169。 2022, Cisco Systems, Inc. 2214 1197_05_2022_c2 DVMRP—Flood amp。 Prune Final Pruned State Source ―S‖ Receiver 1 (Group ―G‖) E X Y A B C D mrouted mrouted mrouted mrouted mrouted mrouted mrouted Truncated Broadcast Tree based on DVMRP route metrics (S, G) Multicast Packet Flow 52 169。 2022, Cisco Systems, Inc. 2214 1197_05_2022_c2 Receiver 2 joins Group ―G‖ Receiver 2 (Group ―G‖) Router Y sends a ―Graft (S, G)‖ Message Graft DVMRP—Grafting Source ―S‖ Receiver 1 (Group ―G‖) E X Y A B C D mrouted mrouted mrouted mrouted mrouted mrouted mrouted Truncated Broadcast Tree based on DVMRP r