Multi-Headed MPTCP Schedulers to Control Latency in Long-Fat / Short-Skinny Heterogeneous Networks

Multi-Path TCP (MPTCP) is a protocol that allows many TCP connections, or flows, to be pooled together and to behave as a single flow from the perspective of the higher network layers. In situations with heterogeneous links, such as networks that combine high-latency infrastructure-based links and direct node-to-node wireless links, the low-latency low-capacity link can be used to reduce mean segment latency and control outlier segment latencies. Optimizing for these statistics requires different scheduling strategies, however, and optimizing one usually comes at the expense of the other. We present and evaluate new MPTCP schedulers that manage the trade-off between minimizing mean latency and controlling outlier latencies, and attempt to capture both benefits simultaneously. Our solution allows the subflows to maintain multiple pointers into the multi-path flow's output queue, each following a different scheduling strategy. Our results show that if the different strategies are properly coordinated we can simultaneously capture some or all of the possible reduction in mean and outlier latencies in the long-fat short-skinny heterogeneous network scenario.