An Enhancement of Multipath TCP Performance in Lossy Wireless Networks

Multipath TCP (MPTCP) is an evolvable technology for bandwidth aggregation on a mobile device. MPTCP naturally and concurrently exploits wireless links via different interfaces (i.e., Wi-Fi and cellular) for data transferring. Theoretically, the MPTCP's aggregated throughput is better or at least equals to the TCP throughput over a link. However, our investigation of MPTCP performance in a lossy wireless environment shows that the theoretical statement does not always hold. Specifically, the aggregation benefit of MPTCP (i.e., in a comparison to TCP) becomes negative when the loss over a link surpasses specific levels. In this paper, we focus on finding the negative region of MPTCP's aggregation benefit by experimental study. Additionally, we propose a loss-aware disabling mechanism to bypass the negativity. The mechanism temporarily switches a wireless link to a backup mode when an observed loss value reaches a threshold. We integrate the mechanism with a state-of-the-art MPTCP implementation and compare the two MPTCPs in various lossy conditions. The evaluation results confirm the effectiveness of the newly proposed mechanism in terms of enhancing goodput and saving resources.