Futurewei Technologies Ericsson Cisco Systems, Inc. Cisco Systems, Inc. Huawei Huawei Swisscom Verizon Inc. SK Telecom LG U+ The document describes a postcard-based telemetry method using packet-marking, referred to as PBT-M. PBT-M does not carry the telemetry data in user packets but sends the telemetry data through a dedicated packet. PBT-M does not require an extra instruction header but claims a bit as a trigger in existing header fields. PBT-M raises some unique issues that need to be considered. This document describes the high level scheme and covers the common requirements and issues when applying PBT-M in different networks. PBT-M is complementary to the other on-path telemetry schemes such as IOAM.