Research On P2P VoD System Based On Mutil-Chord

It is a challenging job to offer a large scale service of VoD(Video on demand) on the internet. The traditional method of VoD is based on the C/S(Client/Server) model, which is facing the bandwidth problem and the server is easy to become a bottleneck. P2P (Peer to Peer) technology breaks the traditional C/S model because it makes each node in the net equal to each other. Not only a node works as a server to serve others but also gets served by others to settle the bandwidth problem very well. P2P technology gets a rapid development because of its expansibility, fault tolerance and robustness etc and is applied in VoD field gradually.This paper has conducted in-depth studies on key problems of P2P VoD, on the base of which, this paper proposes a P2P VoD system (MChordVoD) based on multi-Chord. P2P VoD locates resources inefficiently with a long time span on the present net structure. Aiming at this problem, MChordVoD uses a DHT overlay network(MChord) based on the multi-Chord to locate resources. MChord puts nodes playing the same contents in one Chord. Because when nodes are playing programs using VoD, the searched resources usually has a strong relevancy, the system can further reduce the route length through recording the route information of last retrieving.Considering problems of P2P VoD in the receiver driving model used while data is distributed on the present mesh overlay, the paper proposes a customization and cooperation based data distribution strategy in which data is customized from the sender and when there are nodes at near playing positions the nodes cooperate with each other to finish the video data receiving.Owing to the numerous videos but the small number of peers who watching the same video at near playing positions in VoD system, It lead to only a few peers communication with each other by P2P network. So the P2P network lost its advantages. In this paper, memory cache combine with disk cache is used to cache the data which has been played so as to increase the number of peer who could provide service. And a video popularity based caching strategy was proposed to fulfill the load balancing of the system.Simulated experiments on P2PSIM prove that under the same condition compared with the PROMISE of the same kind, MChordVoD outperforms other systems on the functional indices of starting delay, VCR operating delay and node pressure of supplying programs etc.