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The Internet Group Management Protocol (IGMP) is a communications protocol used by hosts and adjacent routers on IPv4 networks to establish multicast group memberships. IGMP is an integral part of IP multicast and allows the network to direct multicast transmissions only to hosts that have requested them.
In support of link-local multicasts which do not use IGMP, any IPv4 multicast address that falls within the *.0.0.0 / 24 and *.128.0.0 / 24 ranges will be broadcast to all ports on many Ethernet switches, even if IGMP snooping is enabled, so addresses within these ranges should be avoided on Ethernet networks where the functionality of IGMP ...
The multicast tree construction is receiver driven and is initiated by network nodes that are close to the receivers. IP multicast scales to a large receiver population. The IP multicast model has been described by Internet architect Dave Clark as, "You put packets in at one end, and the network conspires to deliver them to anyone who asks." [5]
IGMP snooping is designed to prevent hosts on a local network from receiving traffic for a multicast group they have not explicitly joined. It provides switches with a mechanism to prune multicast traffic from links that do not contain a multicast listener (an IGMP client). Essentially, IGMP snooping is a layer 2 optimization for the layer 3 IGMP.
The LAN Prune receiver delays acting on it for 3 seconds, so that if another LAN router still needs the multicast stream, it can send a PIM Join message to counteract (cancel) the Prune. ("That router doesn't need it, but I still do!") Suppose a router has Pruned, and some time later a receiver requests the multicast stream with an IGMP message.
Multicast is what enables a node on a network to address one unit of data to a specific group of receivers. [1] In interactive multicast at the data link or network layer, such as IP multicast, Ethernet multicast or MBMS service over cellular network, receivers may join and leave the group using an interaction channel.
Modern Ethernet controllers filter received packets to reduce CPU load, by looking up the hash of a multicast destination address in a table, initialized by software, which controls whether a multicast packet is dropped or fully received. Ethernet multicast is available on all Ethernet networks. Multicasts span the broadcast domain of the network.
The Link-Local Multicast Name Resolution (LLMNR) is a protocol based on the Domain Name System (DNS) packet format that allows both IPv4 and IPv6 hosts to perform name resolution for hosts on the same local link.