3Com 8807 Configuration Manual page 420

420 C 39: IGMP S
HAPTER
Implementing IGMP
Snooping
C
NOOPING ONFIGURATION
Figure 103 Multicast packet transmission when IGMP Snooping runs
Multicast router
Layer 2 Ethernet Switch
Video stream
Multicast group member
Related concepts of IGMP Snooping
To facilitate the description, this section first introduces some related switch
concepts of IGMP Snooping.
Router Port: The port of the switch, directly connected to the multicast router.
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Multicast member port: The Ethernet switch port connected to the multicast
■
member. The multicast member refers to a host joined a multicast group.
MAC multicast group: The multicast group is identified with MAC multicast
■
address and maintained by the Ethernet switch.
Router port aging time: Time set on the router port aging timer. If the switch
■
has not received any IGMP general query message when the timer times out, it
considers the port no longer as a router port.
Multicast group member port aging time: When a port joins an IP multicast
■
group, the aging timer of the port will begin timing. The multicast group
member port aging time is set on this aging timer. If the switch has not
received any IGMP report message when the timer times out, it transmits IGMP
specific query message to the port.
Maximum response time: When the switch transmits IGMP specific query
■
message to the multicast member port, the Ethernet switch starts a response
timer, which times before the response to the query. If the switch has not
received any IGMP report message before the timer times out, it will remove
the port from the multicast member ports
Implementing Layer 2 multicast with IGMP Snooping
The Ethernet switch runs IGMP Snooping to listen to the IGMP messages and map
the host and its ports to the corresponding multicast group address. To implement
IGMP Snooping, the Layer 2 Ethernet switch processes different IGMP messages in
the way illustrated in the figure below:
Internet / Intranet
Video stream
Video stream
Video stream
Non-multicast Non-multicast
group member group member
Video stream
VOD Server