Mld Messages - HP A5500 SI Switch Series Configuration Manual

Figure 78 Flow paths of multicast-address-and-source-specific multicast traffic
Source 1
Source 2
In the case of MLDv1, Host B cannot select IPv6 multicast sources when it joins IPv6 multicast group G.
Therefore, IPv6 multicast streams from both Source 1 and Source 2 will flow to Host B whether it needs
them or not.
When MLDv2 is running on the hosts and routers, Host B can explicitly express its interest in the IPv6
multicast data that Source 1 sends to G—denoted as (S1, G), rather than the IPv6 multicast data that
Source 2 sends to G—denoted as (S2, G). Thus, only IPv6 multicast data from Source 1 will be
delivered to Host B.
MLD state
A multicast router that is running MLDv2 maintains the multicast address state per multicast address per
attached subnet. The multicast address state consists of the following items:
Filter mode—The router keeps tracing the Include or Exclude state.
•
List of sources—The router keeps tracing the newly added or deleted IPv6 multicast source.
•
Timers—Filter timer and source timer. The filter timer is the time the router waits before switching to
•
the Include mode after an IPv6 multicast address times out, and the source timer is for source
recording.
Receiver host state listening
By listening to the state of receiver hosts, a multicast router that is running MLDv2 records and maintains
information of hosts joining the source group on the attached subnet.

MLD Messages

The following descriptions are based on MLDv2 messages.
MLD query message
An MLD querier learns the multicast listening state of neighbor interfaces by sending MLD query
messages. In
Packets (S1,G)
Packets (S2,G)
Figure 79, the darker area in the figure shows the format of an MLDv1 message.
Host A
Receiver
Host B
Host C
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