SMC Networks 1000BASE-X 用户手册

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information, and configures multicast filters accordingly. IGMP Snooping 
generates no additional network traffic, allowing you to significantly reduce 
the multicast traffic passing through your switch. 

The Internet Group Management Protocol (IGMP) runs between hosts 
and their immediately neighboring multicast router/switch. IGMP is a 
multicast host registration protocol that allows any host to inform its local 
router that it wants to receive transmissions addressed to a specific 
multicast group. 

A router, or multicast-enabled switch, can periodically ask their hosts is 
they want to receive multicast traffic. If there is more than one router/
switch on the LAN performing IP multicasting, one of these devices is 
elected “querier” and assumes the responsibility of querying the LAN for 
group members.

Based on the group membership information learned from IGMP, a 
router/switch can determine which (if any) multicast traffic needs to be 
forwarded to each of its ports. At Layer 3, multicast routers use this 
information, along with a multicast routing protocol such as DVMRP, to 
support IP multicasting across the Internet.

Note that IGMP neither alters nor routes any IP multicast packets. A 
multicast router/switch must be used to deliver IP multicast packets across 
different subnetworks. 

The TigerStack 100 provides two transmit queues on each port, with a 
weighted round-robin scheme. This function can be used to provide 
independent priorities for various types of data such as real-time video or 
voice, and best-effort data.