EMPTCP: Towards High Performance Multipath Data Transmission by Leveraging SDN

Abstract

Motivated by the poor performance of MPTCP when used for bulk transfers in multipathed networks, in this paper we propose an efficient MPTCP protocol variant named eMPTCP aiming to achieve high throughput, low latency and good bottleneck fairness. The novel MPTCP variant eMPTCP can prevent in-network buffer overflow and packet loss using a distributed and reactive approach for bandwidth allocation and adjusting the congestion window of subflows on multiple paths in a coordinated fashion. It employs ECN feedback and latency (in terms of RTT) to modulate the congestion window via a gamma correction function. This novel congestion- and latency-aware window adjustment mechanism behaves very helpful in handling the traffic bursts, easing the buffer pressure on switches, and greatly mitigates the incast issue. Besides, in this solution SDN is leveraged to compute a set of optimal available routes for subflows and actively adjust the number of subflows of each MPTCP flow according to the instantaneous traffic condition. Moreover, this novel MPTCP protocol variant eMPTCP works well with existing switch hardware and is able to coexist with legacy TCP. It ensures that a multipath flow will not take up more capacity on any shared paths than if it was a single path TCP flow using only one of those paths, which guarantees it will not unduly harm other flows. Simulation results show that eMPTCP achieves smaller MPTCP convergence time, higher aggregate throughput and lower flow completion time than existing legacy competitors, and largely improves the application performance and user experience, making the network more robust and faster.