R3303-HP HSR6800 Routers IP Multicast Configuration Guide

• If it expects 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 expects 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 26,

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 26 Flow paths of source-and-group-specific multicast traffic

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 or not it needs

them.

When IGMPv3 runs 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)). Only multicast data from Source 1

is delivered to Host B.

Enhancements in query and report capabilities

1. Query message carrying the source addresses:

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 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.

Group records include the following categories:

{ IS_IN—The source filtering mode is Include. The report sender requests the multicast data from

only the sources defined in the specified multicast source list.