3Com 5500-SI Configuration Manual page 315

Figure 81 Multicast packet transmission when IGMP Snooping runs
Multicast router
Layer 2 Ethernet Switch
Switch 5500
Video stream
Multicast group member Non-multicast
group member
IGMP Snooping Terminology
Table 308 explains switching terminology relevant to IGMP Snooping.
Table 308 Switching Terminology relevant to IGMP Snooping
Term
Router Port
Multicast member port
MAC multicast group
Router port aging time
Multicast group member port
aging time
Maximum response time
The Switch 5500 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 switch processes different IGMP messages as shown in Figure 82.
Internet / Intranet
Video stream
Video stream
Video stream
Non-multicast
group member
Meaning
The port of the switch, directly connected to the multicast
router.
The port connected to the multicast member. The multicast
member refers to a host that joined a multicast group.
The multicast group is identified with MAC multicast address
and maintained by the Switch 5500.
Time set on the router port aging timer. If the switch has not
received any IGMP general query messages before the timer
times out, it is no longer considered a router port.
When a port joins an IP multicast group, the aging timer of the
port will begin timing. If the switch has not received any IGMP
report messages before the timer times out, it transmits IGMP
specific query message to the port.
When the switch transmits IGMP specific query message to the
multicast member port, the Switch 5500 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
IGMP Snooping 315
Video stream
VOD Server