3Com 10014298 manual Implement Igmp Snooping, Multicast Packet Transmission With Igmp Snooping

IGMP Snooping 125

Figure 29 Multicast Packet Transmission With IGMP Snooping

Video stream

Internet/Intranet

Multicast router

Video stream

VOD server

Layer 2

Ethernet switch

Video stream	Video	Video stream
	stream

Multicast
	Nonmulticast	Nonmulticast
group	group	group
member	member	member

Implement IGMP Snooping

This section introduces related switch concepts of IGMP Snooping:

■Router Port: The port 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 7750.

■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 begins 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 7750 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

The Switch 7750 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, Switch 7750 processes different IGMP messages shown in the figure below: