Efficient Hashing for Dynamic Per-Flow Network-Interface Selection

Although most smartphones today have both cellular data and WiFi capacity, network-selection techniques typically only allow for a single data interface to be used at a time. This leads to several problems including the interruption of existing connections when switching interfaces, complete loss of connectivity when the selected network is not functioning correctly, and significantly less bandwidth to the device than is possible if the available wireless capacity is aggregated. While interface bonding is not new, aggregating two such diverse networks is particularly challenging given that different wireless technologies, and even different networks of the same type, offer inconsistent link parameters, presenting dynamically fluctuating bandwidth, latency, and packet loss. In this paper we present a simple, but extremely efficient, hashing technique for multi-interface packet scheduling. We have implemented our system with aggregation proxies running in well-connected data centers and client code running on a Galaxy Nexus running Android 4.1. Our experimental results show that our prototype never loses connectivity even when networks fail as long as at least one network is functioning, does not break connections as interface selection is adjusted, and can increase bandwidth to the smartphone to the available aggregated network capacities. Transmission time is reduced by up to 60% vs. using a single network interface.