Cisco Systems, Inc. Cisco Systems, Inc. Verizon Wireless ZTE Corp. This document specifies encapsulations for the Simple Two-Way Active Measurement Protocol (STAMP), defined in RFC 8762, and its optional extensions, defined in RFC 8972, in MPLS networks. It specifies the encapsulation of STAMP test packets for point-to-point Label Switched Paths (LSPs) and point-to-point single-segment Pseudowires (PWs), with or without an IP/UDP header, so that the test packets experience the same forwarding and Equal-Cost Multi-Path (ECMP) behavior as the data traffic being measured. In addition, two new MPLS Generic Associated Channel (G-ACh) types are defined. This document updates RFC 8762 for TTL and IPv6 Hop Limit processing and RFC 8972 for the STAMP Session Identifier for LSPs and PWs. This document specifies the requirements for IPv6 STAMP in unauthenticated mode using UDP zero-checksum that deviates from the integrity requirement specified in RFC 6936.