Which of the following functions is not required in a PIM SSM network?

Protocol Independent Multicast - Source-Specific Multicast (PIM SSM) is designed to build a source-based distribution tree directly from the receiver to the source. In the SSM model, the receiver must explicitly specify both the group address (G) and the source address (S) it wishes to receive traffic from, using an (S,G) join. This allows the last-hop router to send a PIM Join message directly upstream toward the source 'S'. Consequently, the PIM-SM concept of a Rendezvous Point (RP), which acts as a meeting point for unknown sources and receivers in a (,G) model, is not used and is not required. The elimination of the RP is a fundamental architectural simplification in PIM SSM.

A. PIM routing protocol: PIM is the fundamental routing protocol that builds the multicast distribution trees. SSM is a specific mode of operation within the PIM protocol suite.
B. SSM translation on the access multicast router: This function, also known as IGMP SSM mapping, is required to support legacy IGMPv1 and IGMPv2 clients, which can only signal (,G) interest, within an SSM domain.
D. IGMP snooping: This is a critical Layer 2 function on switches that prevents multicast traffic from being flooded to all ports, ensuring it is only forwarded toward interested receivers.
E. IGMP Querier: An IGMP Querier is essential on each network segment to solicit membership reports from hosts, allowing the last-hop router to learn which multicast groups are active.

1. Nokia 7750 SR OS R19.10.R1 Services Configuration Guide, Part 2: VPRN, Section: PIM-SSM.

"PIM-SSM is a subset of PIM-SM that supports only source-specific multicast joins. PIM-SSM builds a shortest path tree (SPT) from the receiver to the source. There is no shared tree and no RP is used." (This statement directly confirms that an RP is not used).

"IGMPv3 is not required on the hosts to use PIM-SSM. If only IGMPv1 or IGMPv2 is available on the hosts, the multicast group can be configured as PIM-SSM only on the router. The router can then translate any (,G) join for this group to a (S,G) join." (This confirms the role of SSM translation).

2. RFC 4607: Source-Specific Multicast for IP, Section 1: Introduction.

"The PIM-SSM service model does not require a Rendezvous Point (RP), does not build a shared tree, and does not have source registration. Instead, it builds a shortest-path tree from each receiver to the source." (This is the defining standard for SSM and explicitly states the absence of an RP).