HP A6600 Configuration Manual page 78

If it needs to receive multicast data from specific sources like S1, S2, ..., it sends a report with the
•
Filter-Mode denoted as "Include Sources (S1, S2, ...)".
If it needs to reject multicast data from specific sources like S1, S2, ..., it sends a report with the
•
Filter-Mode denoted as "Exclude Sources (S1, S2, ...)".
As shown in
both of which can send multicast data to multicast group G. Host B is interested only in the multicast data
that Source 1 sends to G but not in the data from Source 2.
Figure 26 Flow paths of source-and-group-specific multicast traffic
Source 1
Source 2
In the case of IGMPv1 or IGMPv2, Host B cannot select multicast sources when it joins multicast group G.
Therefore, multicast streams from both Source 1 and Source 2 will flow to Host B whether it needs them or
not.
When IGMPv3 is running between the hosts and routers, Host B can explicitly express that it needs to
receive the multicast data that Source 1 sends to multicast group G—denoted as (S1, G), rather than the
multicast data that Source 2 sends to multicast group G—denoted as (S2, G). Thus, only multicast data
from Source 1 will be delivered to Host B.
Enhancements in query and report capabilities
Query message carrying the source addresses
1.
IGMPv3 supports not only general queries (feature of IGMPv1) and group-specific queries (feature of
IGMPv2), but also group-and-source-specific queries.
A general query does not carry a group address, nor a source address;
•
A group-specific query carries a group address, but no source address;
•
• A group-and-source-specific query carries a group address and one or more source addresses.
Reports containing multiple group records
2.
Unlike an IGMPv1 or IGMPv2 report message, an IGMPv3 report message is destined to 224.0.0.22
and contains one or more group records. Each group record contains a multicast group address and a
multicast source address list.
Group record has the following types:
IS_IN—The source filtering mode is Include. Namely, the report sender requests the multicast data
•
from only the sources defined in the specified multicast source list.
Figure 26, the network comprises two multicast sources, Source 1 (S1) and Source 2 (S2),
Packets (S1,G)
Packets (S2,G)
Host A
Receiver
Host B
Host C
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