TP-Link T3700G-28TQ T3700G-28TQ V1 UG - Page 226

IGMPv3 Work Process, Leave-Group Mechanism

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2. Leave-Group Mechanism When a host leaves a multicast group in IGMPv2: (1) The host will send leave group message to all the multicast routers in the local network with the multicast address 224.0.0.2. (2) After receiving this leave group message, the querier will send group-specific query message to the multicast group that the host announces to leave. (The querying multicast group address is filled in the destination address field and the group address field of this group-specific query message.) (3) When there are other members of this multicast group in the local network, these members will send their membership report messages after receiving the group-specific query message within the max response time set in the query message. (4) If the querier receives the other member's membership report message of this multicast group within the max response time, the querier will continue to maintain the memberships of this multicast group; otherwise the querier will assume that there is no member in this multicast group and will no longer maintain its memberships.  IGMPv3 Work Process Compatible of and Inherited from IGMPv1 and IGMPv2, IGMPv3 further enhances the control capacity of the hosts and broaden the functions of the query and report messages. 1. Enhancement of the Hosts IGMPv3 adds the filtering mode (INCLUDE/EXCLUDE) for the multicast source basing on the group-specific query. This mode allows the hosts to accept or reject multicast traffic from specified multicast sources when joining a multicast group. When a host joins a multicast group:  If it expects only the multicast data from specified multicast sources, such as S1, S2 ... Its report message can be marked with INCLUDE Sources (S1, S2 ...);  If it doesn't expect any multicast data from the specified multicast sources, such as S2, S2... Its report message can be marked with EXLUDE Sources (S1,S2 ...); As shown in Figure 11-4, there are two multicast sources, Source 1(S1) and Source 2(S2), sending multicast data to multicast group G. Host B is only expecting the multicast data sending from Source 1 to G. 215

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2. Leave-Group Mechanism
When a host leaves a multicast group in IGMPv2:
(1)
The host will send leave group message to all the multicast routers in the local network with
the multicast address 224.0.0.2.
(2)
After receiving this leave group message, the querier will send group-specific query message
to the multicast group that the host announces to leave. (The querying multicast group
address is filled in the destination address field and the group address field of this
group-specific query message.)
(3) When there are other members of this multicast group in the local network, these members
will send their membership report messages after receiving the group-specific query
message within the max response time set in the query message.
(4) If the querier receives the other member’s membership report message of this multicast
group within the max response time, the querier will continue to maintain the memberships of
this multicast group; otherwise the querier will assume that there is no member in this
multicast group and will no longer maintain its memberships.
IGMPv3 Work Process
Compatible of and Inherited from IGMPv1 and IGMPv2, IGMPv3 further enhances the control
capacity of the hosts and broaden the functions of the query and report messages.
1. Enhancement of the Hosts
IGMPv3 adds the filtering mode (INCLUDE/EXCLUDE) for the multicast source basing on the
group-specific query. This mode allows the hosts to accept or reject multicast traffic from specified
multicast sources when joining a multicast group.
When a host joins a multicast group:
If it expects only the multicast data from specified multicast sources, such as S1, S2 … Its
report message can be marked with INCLUDE Sources (S1, S2 …);
If it doesn’t expect any multicast data from the specified multicast sources, such as S2, S2…
Its report message can be marked with EXLUDE Sources (S1,S2 …);
As shown in Figure 11-4, there are two multicast sources, Source 1(S1) and Source 2(S2),
sending multicast data to multicast group G. Host B is only expecting the multicast data sending
from Source 1 to G.
215