IGMPv3and MLDv2 allows a receiver to join a group and specify that it only wants to receive traffic for a group if that traffic comes from a specific source. If a receiver does this, and no other receiver on the LAN requires all the traffic for the group, then the Designated Router (DR) can omit performing a (*,G) join to set up the shared tree, and instead issue a source-specific (S,G) join only.
For IPv4, the range of multicast addresses from 232.0.0.0 to 232.255.255.255 is currently set aside for source-specific multicast. For groups in this range, receivers should only issue source specific IGMPv3 joins. If a PIM router receives a non-source-specific join for a group in this range, it should ignore it.
For IPv6, the multicast prefix FF3x::/32 is currently set aside for source-specific multicast. For groups in this range, receivers should only issue source specific MLDv2 joins. If a PIM router receives a non-source-specific join for a group in this range, it should ignore it.
A Nokia PIM router must silently ignore a received (*, G) PIM join message where G is a multicast group address from the multicast address group range that has been explicitly configured for SSM. This occurrence should generate an event. If configured, the IGMPv2 (MLDv1for IPv6) request can be translated into IGMPv3 (MLDv2 for IPv6). The SR allows for the conversion of an IGMPv2 (*,G) request into a IGMPv3 (S,G) request based on manual entries. A maximum of 32 SSM ranges is supported.
IGMPv3 and MLDv2 also allows a receiver to join a group and specify that it only wants to receive traffic for a group if that traffic does not come from a specific source or sources. In this case, the DR performs a (*,G) join as normal, but can combine this with a prune for each of the sources the receiver does not want to receive.