BGP SR Policy Extensions for State Report

This document extends BGP SR Policy, the same protocol used to configure SR Policies, to report operational state information of SR Policies, Candidate Paths, and Segment Lists. Optional State sub-TLVs, carried within the BGP Tunnel Encapsulation attribute, are introduced in this document to report the operational states (e.g., Down, Inactive, or Invalid) along with their associated reasons of the SR Policies from network elements to controller. These extensions are restricted to operational state reporting and do not alter SR Policy computation, path selection procedures, or the operations of the base BGP protocol.