IGMPv1v2v3

IGMPv1v2v3, or Internet Group Management Protocol versions 1, 2, and 3, is a set of communication protocols used by IP hosts and adjacent routers to establish multicast group memberships. Multicast is a method of sending data to multiple recipients simultaneously, which is more efficient than sending the same data to each recipient individually.

IGMPv1, the first version, was introduced in 1989 and is relatively simple. It allows hosts to join and leave multicast groups, but it does not support leaving a group without leaving all groups. This can lead to inefficiencies in network traffic.

IGMPv2, introduced in 1997, improved upon IGMPv1 by allowing hosts to leave a specific group without leaving all groups. This is known as the "leave group" message. IGMPv2 also introduced the concept of "querier" routers, which are responsible for sending out membership queries to determine which groups are still active.

IGMPv3, introduced in 2000, further enhanced the protocol by allowing hosts to specify the source addresses from which they want to receive multicast traffic. This is known as "source-specific multicast" (SSM). IGMPv3 also introduced the concept of "include" and "exclude" modes, which allow hosts to specify whether they want to receive traffic from a specific set of sources or from all sources except a specific set.

All three versions of IGMP are widely used in modern networks, with IGMPv3 being the most commonly used due to its support for source-specific multicast. However, IGMPv1 and IGMPv2 are still in use in some networks, particularly older ones.