P4-CoDel: Active Queue Management in Programmable Data Planes

Today, networks are still vulnerable to high latencies. An important reason for that is the Bufferbloat problem caused by big packet buffers as part of the forwarding equipment of modern networks. Even if these buffer sizes are configured in a reasonable way, they still have a fixed size which is always a compromise. Indeed, the required buffer size strongly depends on the RTT of the end-to-end network connection. In order to support dynamic buffer sizes and to reduce the negative impact of Bufferbloat, different Active Queue Management (AQM) algorithms have been proposed recently, such as CoDel and PIE. However, these algorithms are typically not available in state of the art network equipment.In this paper we show how recent AQM algorithms can be implemented using P4 programmable network equipment. In consequence, communication networks can be easily enhanced to benefit from state-of-the-art AQM algorithms. To this end, we provide an open-source available implementation of CoDel, one of the most prominent queue management algorithms, in P4. The implementation of such AQMs in P4 data plane hardware enables a massive reduction of latency in many use cases, such as traffic shaping in ISP access networks.