HP A5500 EI Switch Series, Configuration Manual

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Enhancements in control capability of hosts
IGMPv3 introduced two source filtering modes—Include and Exclude. These modes allow a host to join
a designated multicast group and to choose whether to receive or reject multicast data from a
designated multicast source. When a host joins a multicast group, one the following occurs:
•
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 Figure 30 , the network comprises two multicast sources, Source 1 (S1) and Source 2 (S2),
both of which can send multicast data to multicast group G. Host B is interested in the multicast data that
Source 1 sends to G but not in the data from Source 2.
Figure 30 Flow paths of source-and-group-specific multicast traffic
Source 2
Receiver
Host A
Host B
Host C
Packets (S1,G)
Packets (S2,G)
Source 1
In the case of IGMPv1 or IGMPv2, Host B cannot select multicast sources when it joins multicast group
G. Multicast streams from both Source 1 and Source 2 will flow to Host B whether or not it needs them.
When IGMPv3 is running between the hosts and routers, Host B can explicitly express its interest in 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). Only multicast data from Source 1
will be delivered to Host B.
Enhancements in query and report capabilities
1.
Query message carrying the source addresses
IGMPv3 supports not only general queries—a feature of IGMPv1—and group-specific queries—a feature
of IGMPv2, but also group-and-source-specific queries.
•
A general query does not carry a group address or 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.
2.
Reports containing multiple group records
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.