Evaluation of Managing MPTCP Fairness via SDN versus Existing Congestion Control Techniques

The MPTCP Transport Layer protocol allows applications to make use of multiple network interfaces simultaneously, allowing for improved throughput and resilience. MPTCP deploys a number of coupled congestion control algorithms that couple congestion window growth across multiple subflows. This restricts window growth to allow competing TCP flows to attain a fair bandwidth share. We examine the performance of existing algorithms across both shared and disjoint paths, finding that these function reasonably only when the bottleneck is shared and the paths exhibit a low bandwidth-delay product. We then propose using uncoupled congestion control within MPTCP, instead managing fairness within the network using SDN. Experimental validation shows that this approach results in fair sharing across shared and disjoint paths, including those with higher bandwidth-delay products.