China Mobile China Mobile China Mobile Centec Centec Network Slices realized over Segment Routing over IPv6 (SRv6) networks use slice-specific forwarding resources that are selected by a slice indicator carried in the IPv6 packet. For two-way active measurement results to reflect the conditions experienced by traffic within a given network slice, the probe packets generated by the Two- Way Active Measurement Protocol (TWAMP) and the Simple Two-Way Active Measurement Protocol (STAMP) need to be forwarded over the same slice-specific resources as the data traffic they are intended to characterize. This document specifies how a slice indicator is carried in TWAMP and STAMP probe packets so that those packets are forwarded through the resources of a target slice, and it defines the corresponding Session-Sender and Session-Reflector behavior. The procedures are independent of the specific encoding used to carry the slice indicator in the SRv6 data plane.