IP multicast uses the Protocol Independent Multicast
(PIM) routing protocol between routers to determine the path on
the distribution tree that multicast packets take from the source
to the receivers (multicast group members). A Palo Alto Networks®
firewall supports PIM Sparse Mode (PIM-SM) (
RFC 4601), PIM Any-Source Multicast (ASM)
(sometimes referred to as PIM Sparse Mode), and PIM Source-Specific
Multicast (SSM). In PIM-SM, the source does not forward multicast
traffic until a receiver (user) belonging to a multicast group requests
that the source send the traffic. When a host wants to receive multicast traffic,
its implementation of IGMP sends an IGMP Membership report message,
and the receiving router then sends a PIM Join message to the multicast
group address of the group it wants to join.