Huawei Old Dog Consulting This document updates the registration procedure within the IANA "Path Computation Element Protocol (PCEP) Numbers" group of registries. This specification changes some of the registries with Standards Action to IETF Review as defined in RFC 8126. This memo updates RFCs 8231, 8233, 8281, 8623, 8664, 8685, 8697, 8733, 8745, 8779, 8780, 8800, 8934, 9050, 9059, 9168, 9357, 9504, 9603, and 9604 for the same. Designating "experimental use" sub-ranges within code point registries is often beneficial for protocol experimentation in controlled environments. Although the registries for PCEP messages, objects, and TLV types have sub-ranges assigned for Experimental Use, the registry for PCEP Error-Types and Error-values currently does not. This document updates RFC 5440 by designating a specific range of PCEP Error-Types for Experimental Use.