A Fairness-based Congestion Control Algorithm for Multipath TCP

Multipath TCP (MP-TCP) has been introduced as an extension to the legacy TCP transport protocol to support communication through multiple paths under a single connection session. The target is to improve both resource utilization and connection robustness. Several congestion control algorithms (CCAs) have emerged in the literature to adapt subflow rates to congestion conditions on the various paths without negatively impacting competing single-path TCP sources. The challenge is to provide a trade-off among three factors, namely, fairness, responsiveness, and window oscillation. In this paper, we propose a new fairness-based CCA (FCCA) based on the fluid model that improves fairness without degrading the other two metrics. The FCCA tracks the performance on each route and dynamically adapts the respective congestion windows, enhancing the overall performance. The proposed algorithm is implemented in a Linux kernel. Simulation results demonstrate that FCCA is capable of achieving almost maximal fairness (98%) while maintaining responsiveness, unlike existing CCAs.