The Internet Group Management Protocol (IGMP) is a basic multicast protocol of the IP standard. It is defined in RFC 1112 (Version 1), RFC 2236 (Version 2) and RFC 3376 (Version 3).
IGMP is used by IP hosts and adjacent multicast routers to establish multicast group memberships. It is an integral part of the IP multicast[?] specification, like ICMP for simple IP.