Network management strategies depend on a timely and accurate knowledge of the network performance measures. Among these, one of the most relevant is the delay of the links, which unfortunately is not easy to measure with accuracy, especially when considering multi-hop paths. This is a classical networking problem, for which several solutions have been proposed. Nonetheless, we argue in this manuscript that there is still some room for improving accuracy and effectiveness in the measurement. This paper proposes a new solution based on the exploitation of the P4 data plane programming language. The basic idea is to handle lightweight probe packets that are forged ad-hoc at the edge of a link and processed at the other edge. Hosts generate the probe packets that are then exploited by the P4 programs in the switches to implement the measure. This approach provides an accurate and reliable measure of the link transit time, also effective in multi-hop links. In this latter case, we show that the measurement is not influenced much by the packet loss when the network is overloaded, thus providing more reliable results with respect to more conventional tools such as the classical ping utility. The manuscript explains the proposed P4 solution; then, it provides a comparison with several other approaches found in the literature, showing that outperform most of them, and finally show the behavior of the proposed methodology when facing a multi hop network path on a congested network to prove its robustness.
Keywords: Link Delay Measurement; P4; SDN.