Minimizing Application-Level Delay of Multi-path TCP in Wireless Networks: A Receiver-Centric Approach

Multi-Path TCP (MPTCP) has attracted much attention as a promising technology to improve throughput performance of wireless devices that support multi-homed heterogeneous networks. Although MPTCP provides significant increase in network capacity, it may suffer from poor delay performance since the delay tends to be aligned with the worst-performing path: packets delivered through a short-delay subflow have to wait in the reordering buffer for packets being transmitted over a long-delay subflow. In this paper, we investigate the application-level delay performance of streaming traffic over MPTCP, and develop an analytical framework to take into account non-negligible network queuing delay and the interplay of congestion control between multiple subflows. We design a simple threshold-based subflow traffic allocation scheme that aims to minimize user-level delay and develop a receiver-centric traffic splitting control (R-TSC) that can be tuned to user preferences. The client-side R-TSC solution facilitates incremental deployment of low-delay streaming service over MPTCP. Through simulation and testbed experiments using commercial LTE and WiFi networks, we demonstrate significant performance gains over the standard MPTCP protocol.