HP MSR ASM, Configuration Manual, Page: 29 / 493

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• 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 12 , 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 12 Flow paths of source-and-group-specific multicast traffic
In 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.
{
IS_EX —The source filtering mode is Exclude. The report sender requests the multicast data from
any sources but those defined in the specified multicast source list.
{
TO_IN —The filtering mode has changed from Exclude to Include.
{
TO_EX —The filtering mode has changed from Include to Exclude.