PIM Flooding Mechanism and Source Discovery Enhancements

The Protocol Independent Multicast (PIM) Flooding Mechanism (PFM) provides a generic hop-by-hop message exchange framework for distributing multicast information among PIM routers. Existing PFM procedures enable efficient source discovery without reliance on Rendezvous Points, shared trees, or initial data registers. This document specifies enhancements to PFM forwarding behavior to improve efficiency and scalability. In particular, it introduces mechanisms to reduce redundant message transmission over multiple parallel links and extends the encoding of multicast information through additional Type-Length-Value (TLV) structures and sub-TLVs to convey richer flow-related data. These enhancements optimize control-plane overhead while preserving interoperability with existing PFM procedures, enabling more efficient dissemination of multicast state in PIM networks.