3.7. RP Discovery

PIM-SM routers need to know the RP address for each group they have (*,G) state for. This address is obtained via automatic means (e.g., embedded-RP), bootstrap mechanism, or static configuration.

Bootstrap Router (BSR) Mechanism:

1. BSR Election: One router per PIM domain elected as Bootstrap Router
2. RP Candidates: Configured routers periodically unicast candidacy to BSR
3. RP Set Selection: BSR selects RP set and announces in Bootstrap messages
4. Flooding: Bootstrap messages flood hop-by-hop throughout domain
5. Group-to-RP Mapping: Routers use order-preserving hash function to map group addresses to RP set

Benefits:

• Dynamic Configuration: Automatic RP discovery without manual configuration
• Redundancy: Multiple RP candidates for reliability
• Load Distribution: Hash function distributes groups across RPs

note

For complete BSR specification and embedded-RP mechanisms, see RFC 5059 and RFC 3956.