A Measurement Study of Network Coding in Peer-to-Peer Video-on-Demand Systems

In recent years, Peer-to-Peer (P2P) multimedia streaming has become an alternative to cable/satellite TV services. Many P2P streaming applications further provide users with DVD-like operations: play, pause, chapter selection, fast-forward, and rewind. Such a real-time interactive multimedia streaming is commonly referred to as the P2P Video-on-Demand (VoD). To further improve the streaming quality, recent research employs network coding as the key enabling technology. However, the practicality and implementation challenges of network coding received very little attention. In this paper, we present a practical implementation of network coding in a P2P VoD system, VoD+NC, based on which we conduct a measurement study on the actual performance gain provided by network coding. In the meantime, we identify design pitfalls when incorporating network coding into a P2P VoD system. Our study shows that, unlike P2P live streaming, directly applying network coding to a P2P VoD system does not necessarily lead to an immediate improvement in playback quality. With the proper configuration, network coding not only brings the same benefits as it does in P2P live streaming, but also better accommodates the asymmetric interests among peers and simplifies the neighbourhood management.