MPTCP Performance over Heterogenous Subpaths

Today's smartphones are equipped with both Wi-Fi and cellular interfaces, creating usage opportunities for protocols such as Multi-path TCP (MPTCP), which enable devices to use more than one interface concurrently. One of the biggest hurdles in implementing MPTCP is the heterogeneity in performance characteristics that exists across multiple interfaces. This makes the selection of primary interface of paramount importance, as this interface is also used for DNS resolution. In this work, we explore performance and IP reachability over real world networks. Our findings indicate that widespread MPTCP deployment faces significant obstacles. In particular, we perform controlled and real world experiments over multiple paths with differing loss rates and round trip latencies to assess the effect of primary path selection, and the range of issues that arise from selecting the under-performing path. Using results from our experiments, we show how heterogeneous paths can adversely affect MPTCP performance, especially when one path is lossy.