As networks develop and permeate ever deeper many aspects of today’s society, the need for performance monitoring techniques has become crucial in a wide variety of contexts. Among such methods figure Explicit Host-to-Network Flow Measurement techniques (EFM), which allow to extract network metrics from a data transmission without accessing the connection’s endpoints. The objective of this thesis is twofold: on one hand, it involves implementing Spin Bit and Delay Bit, two EFM techniques capable of measuring in-network latency; on the other, it aims to test these techniques on L4S, a state-of-the-art network suite for TCP. This research introduces a functioning implementation of these EFM techniques.