IGMP
The Internet Group Management Protocol (IGMP) is used with IPv4 to control the handling of group membership in the Internet. Version 3, specified in RFC 3376, is supported and is interoperable with Versions 1 and 2. Version 1 of the protocol is specified in RFC 1112, and Version 2 is specified in RFC 2236.
IGMP normally works in an environment in which there are a number of IGMP-capable hosts connected to one or more IGMP routers. The routers forward membership information and packets to other IGMP routers and receive group membership information and packets from other IGMP routers.
The Ixia hardware simulates one or more hosts, while the DUTs are assumed to be IGMP routers. The simulation calls for groups of simulated hosts to respond to IGMP router-generated queries and to automatically generate reports at regular intervals. A number of IGMP groups are randomly shared across a group of hosts.
Version 3 adds the concept of filtering, based on the IP source address, to cut down on the reception of unwanted multicast traffic. This filtering consists of limiting the receipt of packets to only those from specific sources (INCLUDE) or to those from all but specific sources (EXCLUDE). Refer to MLD for information about similar functions for multicast traffic in IPv6 environments.
Compatibility with earlier versions of IGMP is an important part of IGMPv3. The Group Compatibility Modes for an IGMPv3 router are summarized as follows:
- IGMPv3 Compatibility Mode (default): An IGMPv2 and/or IGMPv1 Host is present, but NOT running.
- IGMPv2 Compatibility Mode: An IGMPv2 Host may be present and running. An IGMPv1 Host is present, but NOT running.
- IGMPv1 Compatibility Mode: An IGMPv1 Host is present and running.