Peer-to-Peer Streaming Systems

With advances in the broadband Internet access technology and the coding techniques, video streaming services have become increasingly popular. Traditionally, video streaming services are deployed in the client/server architecture. However, this centralized architecture cannot provide streaming to a large population of users due to the limited upload capacity from the server. Peer-to-Peer (P2P) technology has recently become a promising approach to provide live streaming services or Video-onDemand (VoD) services to a huge number of the concurrent users over a global area. P2P streaming systems can be classified into P2P live streaming systems and P2P VoD systems. In a P2P live streaming system, a live video is disseminated to all users in real time. The video playbacks on all users are synchronized. In a P2P VoD system, users can choose any video they like and start to watch it at any time. The playbacks of the same video on different users are not synchronized. Depending on the approaches of overlay constructions, P2P live streaming systems can be categorized into tree-based P2P live streaming systems and mesh-based P2P live streaming systems. In tree-based P2P live streaming systems, the video streams are delivered over a single application-layer tree or multiple application-layer trees. In mesh-based P2P live streaming systems, each peer exchanges the data with a set of neighbors. VoD services provide more flexibility and interactivity to users. Depending on the forwarding approaches, P2P VoD systems can be categorized into buffer-forwarding systems, storage-forwarding systems, and hybrid-forwarding systems. In P2P VoD systems, prefetching scheme enables peers to download the future segments which are away from the current playback position, thus increasing the playback continuity.