Flow Synchronization for Network Coding

Network Coding (NC) is a means to improve network performance in various ways. Most evaluations so far were done with simplified assumptions about the application scenario, namely equal data rates and packet sizes for traffic to be encoded. Traffic in real networks, however, does not have this property. Hence, as deterministic and random NC require these properties, flows have to be synchronized prior to encoding to guarantee these properties and to be able to benefit from NC in real networks. In this paper, we present a set of algorithms that synchronize arbitrary flows in wired and wireless scenarios for joint encoding later on. These algorithms are based on fragmentation and Active Queue Management (AQM) techniques. To demonstrate the benefits of our approach, we developed an encoder and decoder for deterministic XOR NC that uses this synchronization technique. Simulation results show that with our synchronization techniques, NC, even in scenarios with bursty, self-similar traffic where NC could not have been deployed so far, increases throughput and lowers packet loss and variance of end-to-end delay compared to plain forwarding.