Faster MPTCP sub-flow establishment for interactive applications

MPTCP's ability to bond interfaces regardless of the underlying technologies offers capacity boost and resiliency for applications in multi-access wireless networks. MPTCP connections start with a single master sub-flow that needs to become fully established before any attempt is made to initiate additional sub-flows. The master's path is selected by the host's routing table, which usually reflects static cost metrics instead of the variable capacity or latency of the paths. For sensitive applications, this rigidity may penalize performance compared to an ideal case when the best path is selected dynamically for the master sub-flow. Additionally, if there is any forwarding problem along the default route, MPTCP connections stuck at the handshake even in the presence of usable alternative paths. A potential solution to both problems is to change MPTCP's sequential connection establishment procedure to simultaneous sub-flow creation. As this disrupts the current protocol design, it is especially worth to evaluate the gains achievable by the solution. This work is the first to quantify the potential benefits of simultaneous sub-flow establishment through simulations of interactive web traffic with multi-access devices over Wi-Fi and LTE. Results indicate significantly shorter download times when the default route performs worse than alternative paths.