SMC Networks 8606T, Management Manual

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IGMP Multicast Filtering
Multicasting is used to support real-time applications such as video
conferencing or streaming audio. A multicast server does not have to
establish a separate connection with each client. It merely broadcasts
its service to the network, and any hosts that want to receive the
multicast register with their local multicast switch/router. Although
this approach reduces the network overhead required by a multicast
server, the broadcast traffic must be carefully pruned at every
multicast switch/router it passes through to ensure that traffic is only
passed on to the hosts that subscribed to this service.
This switch uses IGMP (Internet Group Management Protocol) to
query for any attached hosts who want to receive a specific multicast
service. The switch looks up the IP Multicast Group used for this
service and adds any port which received a similar request to that
group. It then propagates the service request on to any neighboring
multicast switch/router to ensure that it will continue to receive the
multicast service. (For more information, see the “IP Multicast
Filtering” section in Chapter 4 of this Users Guide.)