Upon completion you will be able to: Differentiate between a unicast, multicast, and broadcast message; know the many applications of multicasting; understand multicast link state routing and MOSPF; understand multicast link state routing and DVMRP; understand the Core-Based Tree Protocol; understand the Protocol Independent Multicast Protocols; understand the MBONE concept. | Chapter 14 Multicasting And Multicast Routing Protocols CONTENTS INTRODUCTION MULTICAST ROUTING MULTICAST TREES MULTICAST ROUTING PROTOCOLS DVMRP MOSPF CBT PIM MBONE INTRODUCTION Figure 14-1 Unicasting In unicast routing, the router forwards the received packet through only one of its interfaces. Figure 14-2 Multicasting In multicast routing, the router may forward the received packet through several of its interfaces. Figure 14-3:a Multicasting versus multiple unicasting Figure 14-3:b Multicasting versus multiple unicasting Emulation of multicasting through multiple unicasting is not efficient and may create long delays, particularly with a large group. MULTICAST ROUTING MULTICAST TREES In a source-based tree approach, the combination of source and group determines the tree. In the group-shared tree approach, the group determines the tree. MULTICAST ROUTING PROTOCOLS Figure 14-4 Multicast routing protocols DVMRP Figure 14-5 Reverse path forwarding In reverse path forwarding (RPF), the router forwards only the packets that have traveled the shortest path from the source to the router; all other copies are discarded. RPF prevents the formation of loops. Figure 14-6 Reverse path broadcasting Figure 14-7 RPF versus RPB RPB creates a shortest path broadcast tree from the source to each destination. It guarantees that each destination receives one and only one copy of the packet. Figure 14-8 RPF, RPB, and RPM RPM adds pruning and grafting to RPB to create a multicast shortest path tree that supports dynamic membership changes. MOSPF Figure 14-9 Unicast tree and multicast tree CBT Figure 14-10 Shared-group tree with rendezvous router Figure 14-11 Sending a multicast packet to the rendezvous router In CBT, the source sends the multicast packet (encapsulated in a unicast packet) to the core router. The core router decapsulates the packet and forwards it to all interested hosts. PIM PIM-DM is used in a dense multicast environment, such as a LAN environment. PIM-DM uses RPF and pruning/grafting strategies to handle multicasting. However, it is independent from the underlying unicast protocol. PIM-SM is used in a sparse multicast environment such as a WAN. PIM-SM is similar to CBT but uses a simpler procedure. MBONE Figure 14-12 Logical tunneling Figure 14-13 MBONE DVMRP supports MBONE | Chapter 14 Multicasting And Multicast Routing Protocols CONTENTS INTRODUCTION MULTICAST ROUTING MULTICAST TREES MULTICAST ROUTING PROTOCOLS DVMRP MOSPF CBT PIM MBONE INTRODUCTION Figure 14-1 Unicasting In unicast routing, the router forwards the received packet through only one of its interfaces. Figure 14-2 Multicasting In multicast routing, the router may forward the received packet through several of its interfaces. Figure 14-3:a Multicasting versus multiple unicasting Figure 14-3:b Multicasting versus multiple unicasting Emulation of multicasting through multiple unicasting is not efficient and may create long delays, particularly with a large group. MULTICAST ROUTING MULTICAST TREES In a source-based tree approach, the combination of source and group determines the tree. In the group-shared tree approach, the group determines the tree. MULTICAST ROUTING PROTOCOLS Figure 14-4 Multicast routing protocols DVMRP Figure 14-5 Reverse path forwarding .
