Pushing server bandwidth consumption to the limit: Modeling and analysis of peer-assisted VoD

Recent years have witnessed video-on-demand (VoD) as an efficient means for providing reliable streaming service for Internet users. It is known that peer-assisted VoD systems, such as NetFlix and PPlive, generally incur a lower deployment cost in terms of server bandwidth consumption. However, some fundamental issues still need to be further clarified, particularly for VoD service providers. In particular, how far can we push peer-assisted VoD forward, and at the scale of VoD systems, the maximum reduction of server bandwidth consumption that can be achieved with peer-assisted approaches. In this paper, we provide extensive model analysis to understand the minimum server bandwidth consumption for peer-assisted VoD systems. We first propose a basic model that can optimally schedule user demands at given snapshots. Our model analysis reveals the optimal performance bound and shows that the existing peer-assisted protocols are still far from being optimal. How to push the server bandwidth consumption to the limit remains a big challenge in VoD system design. To approach the optimal bandwidth consumption in real deployment, we further extend our model to a realistic case to capture the peer dynamic across continuous time-slots. The simulation result indicates that the optimal load scheduling problem is still achievable through a dynamic programming algorithm. Its design principle further motivates a fast priority-based algorithm that achieves near-optimal performance. These proposed algorithms can significantly reduce the bandwidth consumption of dedicated VoD servers.