Huawei Technologies Huawei Technologies China Mobile Cisco Systems, Inc. ZTE Corporation The Path Computation Element (PCE) provides path computation functions in support of traffic engineering in Multiprotocol Label Switching (MPLS) and Generalized MPLS (GMPLS) networks. The Source Packet Routing in Networking (SPRING) architecture describes how Segment Routing (SR) can be used to steer packets through an IPv6 or MPLS network using the source routing paradigm. A Segment Routed Path can be derived from a variety of mechanisms, including an IGP Shortest Path Tree (SPT), explicit configuration, or a Path Computation Element (PCE). Path identification is needed for several use cases such as performance measurement in Segment Routing (SR) network. This document specifies extensions to the Path Computation Element Communication Protocol (PCEP) to support requesting, replying, reporting and updating the Path Segment ID (Path SID) between PCEP speakers.