TP-Link T3700G-28TQ T3700G-28TQ V1 UG - Page 221
Multicast Routing
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Chapter 11 Multicast Routing Overview of Multicast Routing Protocols Note: The router and router icon mentioned in this chapter represent the router in general or the switch that runs the layer 3 multicast routing protocols. The multicast routing protocols run in layer 3 multicast devices and they create and maintain multicast routes to forward the multicast packets correctly and efficiently. The multicast routing protocols establish routes for the point-to-multipoint transmissions, known as the multicast distributing tree. The multicast routing table consists of a group of (S, G) entries, and (S, G) route represents routing information from source S to group G. If no multicast source is specified, the entry will be described as (*, G) with * representing any multicast source. If the router supports multiple multicast routing protocols, its multicast routing table will contain multicast routes generated from multiple protocols. Multicast routing protocols include protocols as IGMP, PIM, MSDP, DVMRP, and static multicast routing. The domain mentioned in this guide refers to Autonomous System, which contains a group of routers exchanging routing information with the same routing protocol. IGMP stands for Internet Group Management Protocol. It is responsible for members management of IP multicast in the TCP/IP, and is used to establish and maintain the multicast member relationships between the IP host and its directly neighboring multicast routers. PIM (Protocol Independent Multicast) is a typical intra-domain multicast routing protocol among the AS. It provides IP multicast forwarding by leveraging static routes or unicast routing tables generated by any unicast routing protocols, such as RIP (Routing Information Protocol), OSPF (Open Shortest Path First), IS-IS (Intermediate System to Intermediate System) or Border Gateway Protocol (BGP). MSDP (Multicast Source Discovery Protocol) is an intra-domain multicast resolution which aims at the connection of different PIM SM domains and is used to discover the multicast source information among different ASs. DVMRP (Distance Vector Multicast Routing Protocol) is mainly applied in the multicast backbone network of the Internet. The following mainly introduces IGMP, PIM and Static Multicast Routing. Multicast Roles and Models There are several different roles in the multicast transmission: Multicast Source: The sender of the multicast information. Multicast Group Member: All the receivers of the multicast information. Multicast Group: The group consists of the multicast group members. Multicast Router(or the Layer 3 Multicast Device): The router or switch that supports the layer 3 multicast functions, which contains the multicast routing function and the management function of the multicast group members. 210