An Evaluation of Multipath TCP in Lossy Environment

Multipath TCP (MPTCP) has been increasingly adopted in the current and next generation of mobile wireless networks. MPTCP can exploit multiple wireless links for an application; hence it enhances not only the reliability but also the performance of TCP in the same scenario. However, most of the state-of-the-art congestion controls for MPTCP share the same behavior of TCP when a lost packet happens on a path. Therefore, MPTCP also incurs performance degradation when the number of lost packets increases (i.e., the well-known problem of TCP). Comparing to TCP, the deterioration in MPTCP maybe even worse, especially when the loss simultaneously happens on multiple paths. Since the lossy paths likely occur in wireless networks, the improvement of MPTCP in such environment is necessary. In this work, we explore the feasibility of applying a novel approach of handling loss in TCP congestion control to MPTCP. Specifically, we investigate and extend the bottleneck bandwidth round trip time (BBR) algorithm, which reacts to the loss signal in TCP following an estimation model, for MPTCP. We integrate BBR to MPTCP in a new implementation, namely mpbbr. We then evaluation mpbbr under the lossy networks in comparison to the MPTCP with the balia congestion control. The evaluation results show that mpbbr well handles against the lossy conditions as well as outperforms balia in the investigated scenarios.