Definition On Igmp V1.0 And V2.0 - Compex CGX3224 User Manual

Chapter 8 Advanced Configuration for Compex CGX3224
8.2.1

Definition on IGMP v1.0 and v2.0

For IGMP v1.0,
The Internet Group Management Protocol (IGMP v1.0) is used by IP hosts to
report their host group memberships to any immediately neighboring multicast
routers. IGMP is an asymmetric protocol and is specified here from the point
of view of a host, rather than a multicast router.
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 switch will not have any answers to
its query and will delete the Group Destination Addresses (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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