On the Impact of Zero-padding in Network Coding Efficiency with Internet Traffic and Video Traces

Random Linear Network Coding (RLNC) theoretical results typically assume that packets have equal sizes while in reality, data traffic presents a random packet size distribution. Conventional wisdom considers zero-padding of original packets as a viable alternative, but its effect can reduce the efficiency of RLNC or other erasure coding techniques. Our goal is to characterize the overhead generated by this zero-padding under real-traffic traces. These include TCP and UDP traces from traffic at core routers from CAIDA and a collection of video traces for different codecs and video resolution compiled by Arizona State University. Our numerical results show the dependence of the zero-padding overhead with the number of packets combined in a generation using RLNC. Surprisingly, medium and large TCP generations are strongly affected with more than 100% of padding overhead. Although all video traces are affected, our results show that higher resolution video has a lower overhead, due in part to the fact that most of the transmitted data packets are of the maximum size of packet in the network.