Huawei Cisco Systems, Inc. Sympotech University of Liege Databricks Huawei Ostschweizer Fachhochschule - OST In situ measurement is performed by incorporating performance related information into in-flight data packets. This document specifies a new IOAM Option-Type that has a fixed length and can be updated by transit nodes along the path. It enables lightweight monitoring while maintaining a constant length that is not changed in-flight and is not affected by the number of hops in the network.