Internet Group Management Protocol

/ˌaɪ dʒiː ɛm piː/

noun — "managing who joins and leaves network multicast groups."

IGMP (Internet Group Management Protocol) is a communications protocol used in IPv4 networks to manage membership in multicast groups. Multicast allows a single packet stream to be delivered efficiently to multiple recipients without sending separate copies to each host. IGMP enables hosts to report their interest in joining or leaving multicast groups to neighboring routers, which then control the distribution of multicast traffic across the network.