15.2 IPv4 multicast group management function
The multicast group management function learns the existence of multicast group members on a network directly connected to a router by sending and receiving group membership information between routers and hosts. The Switch supports IGMP as a management protocol for implementing the multicast group management function.
IGMP is a multicast group management protocol used between routers and hosts. The router uses queries to join multicast groups and reports of joining/leaving multicast groups from hosts to determine when a host multicast group is joined or left. The router then uses this information to forward or isolate multicast packets.
IGMPv3 is a protocol extended from IGMPv2 to implement IPv4 multicast group management functionality by introducing functionality to filter senders so that multicast packets are only received from specified senders. Because senders can be specified when the joining or leaving of an IPv4 multicast group is reported, IGMPv3 and PIM-SSM can be used in combination to implement more efficient IPv4 multicast forwarding.
The format and setting values for IGMPv2 messages sent by the Switch follows RFC 2236. Likewise, the format and setting values for IGMPv3 messages follow RFC 3376.