Chapter 11 Multicast Routing - TP-Link T3700G-28TQ User Manual

Chapter 11 Multicast Routing

Overview of Multicast Routing Protocols
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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
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There are several different roles in the multicast transmission：
Multicast Source: The sender of the multicast information.
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Multicast Group Member: All the receivers of the multicast information.
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Multicast Group: The group consists of the multicast group members.
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