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Chapter 7
Advanced Configuration for Compex SGX3226
NOTE
Note: IGMPv1 has no leave mechanism. If a host no longer wants to receive
the traffic, it simply quits. If it is the last, the router will not have any
answers to its query and will delete the GDA for that subnet.
For IGMP v2.0,
IGMP v2.0 allows group membership termination to be quickly reported to the routing protocol,
which is important for high-bandwidth multicast groups and/or subnets with highly volatile group
membership.
Multicast routers use IGMP v2.0 to learn which groups have members on each of their attached
physical networks. A multicast router keeps a list of multicast group memberships for each
attached network, and a timer for each membership. "Multicast group memberships" means the
presence of at least one member of a multicast group on a given attached network, not a list of all
of the members.
When a host receives a General Query, it sets delay timers for each group (excluding the all-
systems group) of which it is a member on the interface from which it received the query.
When a router receives a Report, it adds the group being reported to the list of multicast group
memberships on the network on which it received the Report and sets the timer for the
membership to the [Group Membership Interval].
When a host joins a multicast group, it should immediately transmit an unsolicited Version 2
Membership Report for that group, in case it is the first member of that group on the network
When a host leaves a multicast group, if it was the last host to reply to a Query with a
Membership Report for that group, it SHOULD send a Leave Group message to the all-routers
multicast group.
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