A BSR candidate message is seen with a higher priority than the existing BSR. Which of the following describes the action that occurs?

The Protocol Independent Multicast - Sparse Mode (PIM-SM) Bootstrap Router (BSR) election mechanism is preemptive. According to RFC 5059, when a router in a PIM domain receives a Bootstrap message from a candidate BSR, it compares the priority in the message to that of its currently known BSR. If the priority of the new candidate is higher, the router immediately and unconditionally accepts the new candidate as the active BSR for the domain. This ensures that the router with the highest configured priority is always selected as the BSR as soon as its advertisements are received.

A. The BSR election is preemptive; a higher priority candidate does not need to wait for the existing BSR to fail.

B. There is no "bootstrap message wait interval" for preemption; the switch to a higher-priority BSR is immediate.

D. The preemptive behavior based on priority is a fundamental part of the PIM BSR standard and is not a configurable parameter.

1. RFC 5059: Bootstrap Router (BSR) Mechanism for PIM, Section 3.1, "BSR Election", Page 6. The document states: "A router that receives a Bootstrap message first checks the BSR Priority field. If the Priority of the new BSR is higher than the Priority of the existing BSR, the new BSR is unconditionally accepted."

2. Nokia 7750 SR OS R21.10.R1 Multicast Routing Protocols Guide, "PIM > Bootstrap Router (BSR)", Page 128. The guide describes the election process: "The candidate BSR with the highest priority value is elected as the BSR. If the priority values are the same, the candidate BSR with the highest IP address is elected as the BSR." This implies standard, preemptive RFC-compliant behavior.