H3C Technologies H3C S12500-X Series Switches - Manual (Page 62)

52
• If the host 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 the host 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 21 , the network has two multicast sources, Source 1 (S1) and Source 2 (S2). Both of
them can send multicast data to the 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 21 Flow paths of source-and-group-specific multicast traffic
In IGMPv1 or IGMPv2, Host B cannot select multicast sources when it joins the multicast group G, and
multicast streams from both Source 1 and Source 2 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 the 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
• Query message carrying the source addresses
Compatible with IGMPv1 and IGMPv2, IGMPv3 supports general queries and group-specific
queries. In addition, it introduces 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.
• 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 multicast source address list.
{
IS_EX—The source filtering mode is Exclude. The report sender requests the multicast data from
any sources except those defined in the multicast source address list.