Internet Group Management Protocol (IGMP)

Introduction

• IGMP stands for Internet Group Management Protocol,
• IGMP is an important protocol for supporting efficient multicast communication in IP networks.
• Multicasting is a technique used in network communication to deliver packets from a sender to multiple recipients simultaneously. 

Definition

• IGMP is a communications protocol used by IP network hosts and adjacent routers to establish & manage multicast group memberships.

Characteristics

• IGMP operates at the network layer (layer 3) of the OSI model and is used in conjunction with multicast routing protocols such as Protocol Independent Multicast (PIM) and Distance Vector Multicast Routing Protocol (DVMRP) to control multicast group membership and optimize the delivery of multicast traffic.
• There are several versions of IGMP, including IGMPv1, IGMPv2, and IGMPv3. Each version of IGMP has its own features and capabilities, with IGMPv3 being the most recent and comprehensive version.   IGMPv3 includes source filtering capabilities, which allow hosts to specify which sources of multicast traffic they are interested in receiving. IGMPv3 also introduces the ability for hosts to join and leave multicast groups using source-specific multicast (SSM).
• IGMP is supported by most modern network devices, including routers, switches, and hosts.
• IGMP allows multicast routers to dynamically learn about multicast group memberships within their network and forward multicast traffic only to those network segments where there are interested receivers. This helps to conserve network bandwidth and reduce unnecessary multicast traffic.

Working Mechanism

• IGMP enables routers to learn which hosts are interested in receiving multicast traffic for a specific multicast group and to forward the traffic only to the appropriate interfaces on the network.
• IGMP is used by routers to query hosts on a network and learn about the multicast groups they are interested in. Hosts respond to these queries by sending IGMP messages to the router indicating their interest in a particular multicast group.

Use/Function

• IGMP is used to manage and control the multicast group membership of hosts on a network.
• IGMP allows a router to learn which hosts are interested in receiving multicast traffic and which multicast groups they are interested in, and then forward the traffic only to those hosts.