Overview of IGMP
Definition
The Internet Group Management Protocol (IGMP) is a part of the TCP/IP protocol suite used to manage IPv4 multicast group membership. IGMP sets up and maintains membership between receiver hosts and directly connected multicast routers by exchanging IGMP messages between them. IGMP messages are encapsulated in IP packets.
Purpose
IP multicast routing transmits packets from a source to a group of receivers. In the multicast communications model, the sender only needs to send data to a specified destination address and does not need to know the exact locations of the receivers. To forward multicast data packets to the receivers, the multicast router connected to the network segment of receiver hosts must know which receiver hosts are present on the network segment and ensure that these hosts have joined the specific group. IGMP implements this by setting up and maintaining membership between receiver hosts and directly connected multicast routers. Figure 1 indicates how the IGMP protocol is deployed on a multicast network.
