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Internet Group Management Protocol (IGMP) is a way to restrain broadcast or multicast traffic in a switched network. With unicast traffic, an Ethernet switch learns MAC addresses by looking into the source address field of every frame. However, with multicast packets the Ethernet switch must deal with a multicast MAC header which may or may not appear in its table. Consequently, multicast packets are copied and transmitted or “flooded” to every port. During multicast floods or transmissions devices are unable to use the network, thus wasting bandwidth at best and preventing control data from being sent at worst. The effect of multicast floods is particularly bad with full-duplex links, because the bandwidth consumed is proportional to the number of attached nodes which each invite a multicast packet.
IGMP prevents a flood of packets from congesting a network segment where a node is not interested in receiving the packets. IGMP is an integral part of IP and is used by routers to report their multicast status to nearby routers. continue »
Keywords: connection, Definition, Ethernet, Ethernet Switches, IGMP Snooping, Multicast, MyTnConnection, Networks, Packets, Products, Transition Networks, Transmit, Unicast
