IGMPv3

The Internet Group Management Protocol (IGMP) is a used by hosts and adjacent routers on IPv4 networks to establish multicast group memberships. IGMP is an integral part of IP multicast.

IGMP can be used for one-to-many networking applications such as online streaming video and gaming, and allows more efficient use of resources when supporting these types of applications.

IGMP is used on IPv4 networks. Multicast management on IPv6 networks is handled by Multicast Listener Discovery (MLD) which is a part of ICMPv6 in contrast to IGMP's bare IP encapsulation.

A network designed to deliver a multicast service using IGMP might use this basic architecture:

IGMP operates between a host and a local multicast router. Switches featuring IGMP snooping derive useful information by observing these IGMP transactions. (PIM) is then used between the local and remote multicast routers, to direct multicast traffic from hosts sending multicasts to hosts that have registered through IGMP to receive them.

IGMP operates on the network layer, just the same as other network management protocols like .

The IGMP protocol is implemented on a particular host and within a router. A host requests membership to a group through its local router while a router listens for these requests and periodically sends out subscription queries. A single router per subnet is elected to perform this querying function. Some multilayer switches include an IGMP querier capability to allow their IGMP snooping features to work in the absence of an IP multicast capability in the larger network.

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