Cisco Systems, Inc. Cisco Systems, Inc. Bell Canada Universita di Roma "Tor Vergata" Huawei Segment Routing (SR) leverages the source routing paradigm. RFC 6374 specifies protocol mechanisms to enable the efficient and accurate measurement of packet loss, one-way and two-way delay, as well as related metrics such as delay variation in MPLS networks using probe messages. This document utilizes these mechanisms for Performance Delay and Loss Measurements in Segment Routing networks with MPLS data plane (SR-MPLS), for both SR-MPLS Links and end-to-end Paths including SR-MPLS Policies. In addition, this document defines Return Path TLV for two-way performance measurement and Block Number TLV for loss measurement.