Huawei Technologies Huawei Technologies Huawei Technologies Etheric Networks Tencent Holdings Ltd. Expedia, Inc. HPE Telus Communications Mobile TeleSystems JLLC LLC "Lifetech" The Path Computation Element (PCE) is a core component of a Software- Defined Networking (SDN) system. It can compute optimal paths for traffic across a network and can also update the paths to reflect changes in the network or traffic demands. PCE was developed to derive paths for MPLS Label Switched Paths (LSPs), which are supplied to the head end of the LSP using the Path Computation Element Communication Protocol (PCEP). SDN has a broader applicability than signaled MPLS traffic-engineered (TE) networks, and the PCE may be used to determine paths in a range of use cases including static LSPs, segment routing (SR), Service Function Chaining (SFC), and most forms of a routed or switched network. It is, therefore, reasonable to consider PCEP as a control protocol for use in these environments to allow the PCE to be fully enabled as a central controller. This document describes general considerations for PCECC deployment and examines its applicability and benefits, as well as its challenges and limitations, through a number of use cases. PCEP extensions required for stateful PCE usage are covered in separate documents. This is a living document to catalogue the use cases for PCECC. There is currently no intention to publish this work as an RFC.