Research On Quality Of Service Of Peer-to-Peer On-Demand Streaming Media

Audio and video stream distribution is a kind of important application in Internet, there is however no efficient solution. The server often becomes the bottleneck in a traditional client-server streaming system; the deployment of IP multicast is still limited due to several fundamental concerns such as hard to implement reliable multicast and congestion control; and the Internet content providers can not afford the expensive charge of CDN. Because P2P streaming media can provide service to others with one peer's bandwidth without changing the current Internet deployment; it contains great potential, has wide application foreground. On the other hand, the service capabilities of peers are limited and heterogeneous, and peers can join or leave the system at any time, at the same time, streaming media is a special application with stringent resources requirements for its long last time and playback deadlines, all these make P2P streaming media system face a lot of challenges. Therefore, how to deal with these challenges and guarantee peers' QoS have been important tasks in P2P on-demand streaming media application. The dissertation studies these problems thoroughly and gives some efficient solutions.According to the problem of QoS-aware overlay construction, a two-stage peer selection (TSPS) algorithm and a peer location scheme based on multi-ring (RNLS) are proposed. TSPS algorithm selects suppling peers according to their cache states and steaming QoS, that is, the first stage of TSPS determines available peers according to peers' playout position and the second stage determines the most suitable peers according to some QoS metrics such as peers' bandwidth, delay and loss rate. RNLS is a distributed membership service, in which each peer maintains a data-exchange-ring to explore appropriate data suppliers and several playback-skip-rings with power law radius to assist the quick relocation of VCR operations. Gossip-based method is adopted to exchange message between peers.Because of limited service ability of peers, multiple contents peers are required to be synchronized to send packets to a request peer. The primary challenge in design of a multi-source streaming mechanism is that available bandwidth from each peer is not known a priori, and could significantly change during a session. This dissertation investigates the problem of how to optimally allocate the media streaming among the multiple suppliers, the goal of which is to maximize the priority sum of blocks received ahead of their deadline under heterogeneous bandwidth constraints. Two algorithms are proposed to archive this goal: Multi-Supplier Scheduling (MSS) algorithm based on pull and Push-Pull Multi-Supplier Scheduling (PPMSS) algorithm based on push-pull.Since videos are typically large and have stringent QoS requirements for delivery, many peers may be unable to cache them as a whole to overcome the problem of network jitter and serve others. The QoS-aware replication problem for P2P on-demand systems is formally specified, the goal of which is to satisfy access time deadlines for all nodes while maximize the probability of the successful block requests. A novel caching mechanism is proposed to achieve the goal, which includes a prefetching algorithm and a cache replacement algorithm. In particular, emergency level De and contribution degree Dc of blocks are defined, and used in both algorithms to decide which block should be requested or removed.Prevalent free riding in P2P systems can bring significant degradation in performance. In this paper a P2P VoD incentive mechanism GBIM is proposed, which discourages free riding by letting peers favor uploading to other peers who have proven to be good uploaders according to its responsivity as well as upload bandwidth. Simulation results indicate that GBIM can significantly improve system utility.Through simulation and comparison, performances of both algorithms are illustrated well. Results of our research work will provide a good theoretical and practical reference for P2P on-demand streaming media applications in the future.