Research On P2P VoD Content Discovery Mechanism Based On The Double Layer Overlay Network

The Internet service Video-on-Demand(VoD) provides users for interactive operations, which means users could randomly choose which parts of the movie they want to watch. And now it has become one of the most popular applications on the internet. In the P2P VoD, there is a great playback difference among the users who watch the same movie. This difference challenges peers to share their resources. At the same time, the peer’s skipping operations could lead to that the neighbor peers unable to provide the movie data because of they haven’t cached the data of the new playback position. So how to quickly and efficiently find the neighbors which have cached the resources to provide movie data when peers skip into a new position is one important issue in P2P VoD.In order to deal with above issues, this paper towards two aspects to research. They are the organization of the overlay network and the content discovery. Firstly this paper proposes one double layers overlay network for the P2P VoD node structure. That is putting the peers together to form one playback cluster according to their playback position and building one double-linked cluster-head overlay network as indexing. Then this paper designs a content discovery mechanism to support user’s dragging-on-demand operations. This mechanism is divided into two aspects: inner-swarm lookup and intra-swarm lookup according to the skipping distance. Inner-swarm lookup uses a method like gossip to find aimed neighbors through the swarm and intra-swarms lookup uses one routing table to find the neighbors. The main ideas of intra-swarm lookup mechanism are setting cluster keys and transforming the content discovery into cluster keys searching through the double-linked overlay network of cluster-heads. These two aspects are closely related and complementary. Because the good organization of the overlay network can avoid the playback difference among peers to improve data sharing rate and the efficient content discovery also needs reasonable organization structure to support.Finally, this paper uses "lookup overhead","server payload","lookup delay","playback fluency" as factors to test the function of proposed overlay network and the performance of content discovery algorithm through simulation experiments. Comparing with the typical P2VoD system, it shows much better results.