3Com Switch 8800 Configuration Guide Chapter 24 IGMP Snooping Configuration
24-2
Internet / Intranet
Video stream
VOD Server
Layer 2 Ethernet Switch
Video stream
Multicast group member Non-multicast
group member
Multicast router
Video stream Video stream
Video stream
Non-multicast
group member
Figure 24-2 Multicast packet transmission when IGMP Snooping runs
24.1.2 Implement IGMP Snooping I. Related concepts of IGMP Snooping
To facilitate the description, this section first introduces some related switch concepts of
IGMP Snooping:
z Router Port: The port of the switch, directly connected to the multicast router.
z Multicast member port: The port connected to the multicast member. The
multicast member refers to a host joined a multicast group.
z MAC multicast group: The multicast group is identified with MAC multicast
address and maintained by the Ethernet switch.
z Router port aging time: Time set on the router port aging timer. If the switch has
not received any IGMP general query message before the timer times out, it
considers the port no longer as a router port.
z 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 before the timer times out, it transmits IGMP specific query
message to the port.
z 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