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Multicast Configuration
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 the hosts which subscribed
to this service.
This switch uses IGMP (Internet Group Management Protocol) to
query for any attached hosts that want to receive a specific
multicast service. It identifies the ports containing hosts requesting
to join the service and sends data out to those ports only. It then
propagates the service request up to any neighboring multicast
switch/router to ensure that it will continue to receive the multicast
service. This procedure is called multicast filtering.
The purpose of IP multicast filtering is to optimize a switched
network’s performance, so multicast packets will only be
forwarded to those ports containing multicast group hosts or
multicast routers/switches, instead of flooding traffic to all ports in
the subnet (VLAN).
Configuring IGMP Parameters
You can configure the switch to forward multicast traffic
intelligently. Based on the IGMP query and report messages, the
switch forwards traffic only to the ports that request multicast
traffic. This prevents the switch from broadcasting the traffic to all
ports and possibly disrupting network performance.
b_mgmt.book Page 113 Tuesday, July 8, 2003 5:24 PM
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