Path Computation Element Communication Protocol (PCEP) extensions for Circuit Style Policies

Segment Routing (SR) enables a node to steer packet flows along a specified path without the need for intermediate per-path states, due to the utilization of source routing. An SR Policy can consist of one or a set of candidate paths, where each candidate path is represented by a segment list or a set of segment lists, which are essentially instructions that define a source-routed path. This document specifies a set of extensions to the Path Computation Element Communication Protocol (PCEP) for Segment Routing Policies that are designed to satisfy requirements for connection-oriented transport services (Circuit-Style SR policies). They include the ability to control path modification and the option to request a strict hop-by-hop path, being also applicable for generic SR policy use cases where controlling path modification or deterministic and persistent path requirements are applicable.