How Can Peers Assist Each Other in Large-Scale P2P-VoD Systems

A new genre of P2P systems, P2P Video-on-Demand (P2P-VoD), has not only received substantial recent research attention, but also been implemented and deployed with success in large-scale real-world streaming systems, such as PPLive. The essential characterization of P2P-VoD systems is to take full advantage of peer upload bandwidth contribution with a cache on each peer. Meanwhile, the asynchronous playback of each peer dilutes the peers' ability of assisting each other. How can peers assist each other in large-scale P2P-VoD systems? In this paper, we seek to develop a tractable analytical model and present a simple close-form expression of the average peer contribution, to help us form an in-depth understanding of peer contribution in large-scale P2P-VoD systems. Our analytical results are cross-validated by our extensive simulation studies in large-scale scenario.