SMC Networks 8606SX - annexe 1, Руководство по управлению

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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 which 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 the hosts which 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 “IGMP
Snooping and IP Multicast Filtering” on page 4-6.)