Internet Group Management Protocol

The Internet Group Management Protocol (IGMP) is a network protocol of the Internet protocol suite and is used to establish the multicast groups. IGMP uses ICMP as the Internet Protocol ( IP) and is a component of IP on all hosts that support the reception of IP multicast.

Use

The Internet Group Management Protocol is based on the Internet Protocol ( IP), enabling IPv4 multicast ( group communication ) on the Internet. IP multicasting is the distribution of IP packets with an IP address to multiple stations simultaneously. IGMP provides the ability to dynamically manage groups. The administration is not in the transmitting station instead, but in the routers to which recipients of a multicast group are connected directly. IGMP provides functions with which a station notifies a router that it wants to receive multicast IP packets of a particular multicast group. Multicast routing protocols ( DVMRP, MOSPF, PIM ) take over the coordination of communication between the routers. The sender of multicast IP packets do not know this, how many and which stations receive its packets, because it sends a single packet to its parent router. It duplicates the IP packet as needed when he has multiple outgoing interfaces with receivers.

IPv6 system is integrated in ICMPv6 Multicast Listener Discovery (MLD) use, which operates in a manner similar to the IGMP.

There are three versions of IGMP with the following basic characteristics:

  • IGMPv1 host can join a MC group. Logging out is not implemented here. After a timeout, the host is discharged again.
  • IGMPv2 host can now log out of the MC group ( Leave Message implemented). Therefore multicasts may be treated with a large bandwidth.
  • Here IGMPv3 can now be set, is desired by which the source of the multicast stream. This is an important safety aspect, if not the best.

Packet format

IGMP packets ( in version 1 and version 2) have a size of 64 bits. The following format is used:

The following values ​​for the type may be accepted:

IGMP packets, such as ICMP encapsulated in IP datagrams and use the IP protocol number of 2

Internet Control Message Protocol Host (network) Communication source Distance Vector Multicast Routing Protocol Multicast Open Shortest Path First Network packet Response time (technology)
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