3Com 400 Family, Configuration Manual

Page: 126 / 344

124 C
HAPTER
7: IGMP S
NOOPING
Figure 33 Multicast packet transmission when IGMP Snooping runs
IGMP Snooping Terminology
Table 127 explains switching terminology relevant to IGMP Snooping.
The Switch 4500 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 34 .
Table 127 Switching Terminology relevant to IGMP Snooping
Term Meaning
Router Port The port of the switch, directly connected to the multicast
router.
Multicast member port The port connected to the multicast member. The multicast
member refers to a host that joined a multicast group.
MAC multicast group The multicast group is identified with MAC multicast address
and maintained by the Switch 4500.
Router port aging time 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.
Multicast group member port
aging time 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.
Maximum response time When the switch transmits IGMP specific query message to
the multicast member port, the Switch 4500 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
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
Switch 4500