Huawei Quidway S5600 Series Operation Manual page 446

Operation Manual – Multicast Protocol
Quidway S5600 Series Ethernet Switches-Release 1510
I. Multicast router election mechanism on a shared network segment
A shared network segment is a network segment with multiple multicast routers. In this
case, all routers running IGMP on this network segment can receive the membership
report messages from hosts. Therefore, only one router is necessary to send
membership query messages. In this case, the querier selection mechanism is
required to specify a router as the querier.
In IGMP Version 1, the multicast routing protocol selects the querier. In IGMP Version 2,
it is defined that the multicast router with the lowest IP address is selected as the
querier when there are multiple multicast routers in a network segment.
II. Leave group mechanism
In IGMP Version 1, hosts leave the multicast group quietly without informing any
multicast router. Only when a query message times out can the multicast router know
that a host has left the group. In IGMP Version 2, when a host replying to the last
membership query message decides to leave a multicast group, it will send a leave
group message to the multicast router.
III. Group-specific query
In IGMP Version 1, a multicast query message of the multicast router aims at all the
multicast groups in the network segment. This query is called general query.
IGMP Version 2 adds group-specific query, where the IP address of a multicast group is
taken as the destination IP address and the group address domain of the query
message, to prevent the member hosts of other groups from responding to this
message.
IV. Maximum response time
The Maximum Response Time field is added in IGMP Version 2. It is used to
dynamically adjust the maximum time for a host to respond to the membership query
message.
6.1.3 Working Procedure of IGMP
The working procedure of IGMP is as follows:
The receiver host reports the membership to its shared network.
A querier (IGMPv2) is selected from all the IGMP-enabled routers in the same
network segment.
The querier periodically sends group member query messages to the shared
network segment.
The receiver host responds to the received query message to report the group
membership.
Huawei Technologies Proprietary
6-2
Chapter 6 IGMP Configuration