H3C S5500-EI Series Operation Manual page 96

Operation Manual – Multicast
H3C S5500-EI Series Ethernet Switches
is interested only in the multicast data that Source 1 sends to G but not in the data from
Source 2.
Source 1
Source 2
Figure 6-2 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 it needs them or not.
When IGMPv3 is running between the hosts and routers, Host B can explicitly express
its interest in the multicast data Source 1 sends to multicast group G (denoted as (S1,
G)), rather than the multicast data Source 2 sends to multicast group G (denoted as (S2,
G)). Thus, only multicast data from Source 1 will be delivered to Host B.
II. 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, 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.
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 record types include:
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
Packets (S1,G)
Packets (S2,G)
Receiver
6-5
Chapter 6 IGMP Configuration
Host A
Host B
Host C