Alcatel OmniStack 6124, User Manual

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IGMP Multicast Filtering
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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 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 that 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 Protocol” on page 4-5.)
Configuring IGMP
This protocol allows a host to inform its local switch/router that it wants to receive
transmissions addressed to a specific multicast address group. Use the IGMP
Configuration screen to set key parameters for multicast filtering as shown below.
Note: The default values are indicated in the sample screen.
Parameter Description
IGMP Status If enabled, the switch will monitor network traffic to determine which hosts want
to receive multicast traffic.
Act as IGMP Querier* If enabled, the switch can serve as the “querier,” which is responsible for asking
hosts if they want to receive multicast traffic.
IGMP Query Count The maximum number of queries issued for which there has been no response
before the switch takes action to solicit reports.
IGMP Report Delay The time (in seconds) between receiving an IGMP Report for an IP multicast
address on a port before the switch sends an IGMP Query out that port and
removes the entry from its list.
* This function is not available for the current firmware release.