In a shared network, what mechanism does PIM-SM use to prevent duplicate traffic?( Single choice questions).

The PIM Assert mechanism is used to prevent duplicate multicast traffic on a shared network segment (multi-access network). When multiple routers are connected to the same segment, they might all try to forward the same multicast packet. If a router receives a multicast packet on an interface that it is also using to forward that packet, it initiates the Assert process. Routers on the segment exchange Assert messages to elect a single, unique forwarder for that multicast group, thereby eliminating data duplication.

A. The Register mechanism is used by a first-hop router to encapsulate and send multicast packets to the Rendezvous Point (RP), not to prevent duplicates on a shared link.
B. The BSR/RP mechanism is a dynamic method for discovering and advertising the Rendezvous Point (RP) in a PIM-SM domain, unrelated to duplicate traffic prevention.
D. The Join/Prune mechanism is used by routers to signal interest in receiving multicast traffic for a group, which helps build the distribution tree but does not resolve multiple forwarders.

1. Huawei HedEx Documentation, CloudEngine 8800, 7800, 6800, 5800 Series Switches V200R021C10 Configuration Guide - IP Multicast, "PIM Configuration > Configuring PIM-SM > (Optional) Configuring the PIM Assert Function". This section states: "On a broadcast network, if a device receives a multicast packet from the downstream interface that is the same as the multicast packet sent by the device, an Assert election is triggered... The winner becomes the unique forwarder of subsequent multicast packets on the shared network segment."

2. Huawei HedEx Documentation, NE40E V800R012C10 Configuration Guide - IP Multicast, "PIM Configuration > PIM-SM Configuration > Assert Mechanism". This guide explains: "The Assert mechanism ensures that only one of the PIM routers that are attached to the same network segment forwards multicast packets from a certain multicast source to this network segment."