Appendix A. Functionality Removed from RFC 4601
This appendix documents the functionality that was present in RFC 4601 but has been removed in this specification due to lack of sufficient deployment experience.
Removed Features
(,,RP) State: The (,,RP) state was an optimization to reduce state when multiple groups shared the same RP. Due to minimal deployment, this feature has been removed.
PIM Multicast Border Router (PMBR): PMBR functionality was designed to connect PIM-SM domains with other multicast routing protocols. This has been removed due to lack of deployment.
IPsec Authentication: RFC 4601 described using IPsec to authenticate PIM messages. This has been removed because other authentication mechanisms are more commonly used in practice.
Rationale
These features were removed to simplify the specification and focus on functionality that has proven deployment experience. Implementers should refer to RFC 4601 if they need to support these legacy features for backward compatibility.
For complete details on removed functionality and migration guidance, see Appendix A of RFC 7761.