Flow Synchronization for Network Coding
Thorsten Biermann, Martin Dräxler, Holger Karl · Journal of Communications · 2009
Abstract—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 synchronizedprior toencodingtoguarantee theseproperties 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. Index Terms—network coding, deterministic, random, intersession, flow, packet, synchronization probably most famous of them is the butterfly topology (Figure 1). Although we will focus on this topology in the course of this paper, our techniques can simply be applied in other topologies suitable for linear NC [4]. They all have in common that two plain flows are multicast at a certain node and that these plain flows are jointly encoded at a node that receives both of them. Finally, the encoded flow is decoded again where both the encoded and one of the two plain flows are received.