A Pull-Based Approach for a VoD Service in P2P Networks

We study a new approach to provide an efficient VoD service to a large client population in P2P networks. Previous work has suggested to construct a multicast tree to distribute the video to clients. However, a multicast tree usually requires the central server to perform complex algorithms to add new clients to the tree. In this paper, we show how to simplify the algorithm performed by the server and, at the same time, achieve an efficient use of the system resources. For this purpose, we present a new pull-based approach, called PBA. The basic idea of PBA is quite simple. When a new client wishes to receive a video, the new client contacts first the server. If there is enough left over bandwidth along the path to the new client, the server transmits the video to the new client. Otherwise, the server provides to the new client a list of candidate servants chosen at random. These servants are clients that have received or are currently receiving the video. The new client then searches for an available servant to download the video from. We compare PBA to P cast, a multicast-tree based approach proposed previously. We investigate via intensive simulations the efficiency of both approaches in terms of percentage of rejected clients and of bandwidth consumption. PBA does not only simplify the algorithm performed at the server, but also consumes less bandwidth and allows more clients to access the service. keywords: Video on-demand service, Peer-to-peer networks, Multicast tree, Per-