IGMP specifies how a host can register with a router in order to receive specific multicast traffic. IGMP is an IETF standard , where IGMPv1 is defined in RFC 1112, IGMPv2 in RFC 2236 and IGMPv3 in RFC 3376.
When you troubleshoot multicast networks, it is good to consider the signaling protocol used in the network and packet flows (source and receiver ). The signaling protocol is used to setup and tear down the multicast sessions (such as PIM dense mode, PIM sparse mode, and DVMRP), and packet flow is the actual sending, replicating, and receiving of the multicast packets between the source and receiver, based on the forwarding table created by the signaling process.
Adam, Paul (2014-07-12). All-in-One CCIE V5 Written Exam Guide (Kindle Locations 1976-1981). . Kindle Edition.