Cisco Systems, Inc. Cisco Systems, Inc. ZTE Corporation Huawei Technologies Nokia This document specifies extensions to the Path Computation Element Communication Protocol (PCEP) to support Segment Routing (SR) with a focus on the use of Segment Identifiers (SIDs) and SR-Algorithms in Traffic Engineering (TE). The SR-Algorithm associated with a SID defines the path computation algorithm used by Interior Gateway Protocols (IGPs). This document proposes an approach for informing PCEP peers about the SR-Algorithm associated with each SID used, as well as signaling a specific SR-Algorithm as a constraint to the PCE. The mechanisms for specifying SR-Algorithm constraint is allowing refined path computations that meet specific operational needs, such as low-latency or high-bandwidth paths mostly based on operator- defined criteria using Flexible Algorithms.