What protocol is utilized for managing multicast group memberships?

The correct answer is the Internet Group Management Protocol (IGMP), which is specifically designed for managing multicast group memberships. In networking, multicast allows a single data transmission to be sent to multiple recipients efficiently. IGMP is part of the Internet Protocol suite and is used by hosts and adjacent routers on an IP network to establish and control the membership of hosts in multicast groups.

When hosts want to receive data from a multicast address, they signal their intention by sending IGMP messages. These messages inform the local router to add the host to the multicast group, which allows efficient data delivery since the router can distribute the multicast traffic only to those hosts that have expressed interest in it. This is crucial in environments like digital audio networks, where multiple devices may need to receive the same audio streams simultaneously without congesting the network with redundant transmissions.

Other protocols mentioned do not serve this specific purpose. HTTP is used for transferring hypertext documents on the web, TCP is a transport layer protocol that ensures reliable delivery of data packets, and FTP is focused on transferring files. None of these facilitates multicast group management like IGMP does.