P4air: Increasing Fairness among Competing Congestion Control Algorithms

Congestion control algorithms are usually developed in isolation without thoroughly investigating their co-existence and interactions with other protocols and/or congestion control algorithms. As a result, flows using different algorithms and/or having different Round-Trip Times may overpower each other, resulting in unfair resource distribution, with a subset of the flows usually claiming most of the capacity. To solve the aforementioned problem, we make use of programmable switches and the network programming language P4 to enforce fairness from within the network itself, instead of from the congestion control algorithms ran at the end-points. Our solution P4air continuously monitors the properties of all flows that pass through a switch and groups them based on the behavior of the congestion control algorithms used. Furthermore, for each group, it applies appropriate measures to suppress the aggressive flows and boost smaller flows. Our experiments, using modern programmable hardware (Barefoot Tofino switch), demonstrate significant performance gains for P4air in terms of fairness compared to state-of-the-art solutions.

I. Introduction

The field of congestion control – a key component of transport-layer protocols – continues to see innovation through many novel proposals, each claiming superiority for specific applications or scenarios [1], [2], [7], [13], [14], [20], [25], [29], [30], [41], [42], [44], [51], [55], [59], [63], [65]–[67]. Furthermore, new transport protocols, such as QUIC and MPQUIC, facilitate quick development of new transport features directly from the user space, enabling even more customization and more diverse network protocols in the future [12], [33], [62].