Research On Kev Technologies Of Content Distribution In P2P Network

Nowadays peer-to-peer (P2P) content distribution has become one of the most influential technologies on Internet. Compared with the traditional C/S and CDN architectures, P2P technology has the advantages of high efficiency, good scalability and easy deployment. BitTorrent (BT) has been the most popular P2P system, and both P2P-based file sharing and real-time streaming service have become the main application types that consume one of the largest fractions of Internet traffic.However, since peers have very limited and heterogeneous upload bandwidth, different users or applications have different requirements, such as bandwidth, delay, transmission duration, there are still some difficulties and challenges to provide high quality services. Based on above reasons, we focus on how to analyze and optimize the efficiency of point-to-multipoint content distribution in P2P network. We study the key technologies involved in BitTorrent system and the applications of file sharing and live streaming, e.g., overlay construction, bandwidth allocation, data scheduling. More specifically, the contribution of this thesis lies in the following three aspects.First, we deduce the piece diffusion and the upload utilization models based on the upload bandwidth of peers, and propose improved strategies for overlay construction and incentive mechanism. The derived models can reveal the delicate relationship between some key parameters, such as TFT round, maximum concurrent uploading number, piece size; the proposed overlay construction strategy UC-track algorithm can optimize the topological features of the BitTorrent overlay and improve the efficiency of data transmission in BitTorrent system; the proposed incentive mechanism PU algorithm, which consists of bandwidth limitation strategy and bandwidth allocation strategy, can significantly improve the fairness of BitTorrent system whereas the load on the seed is reduced considerably.Furthermore, we generalize the BitTorrent system into a common P2P system. As to file sharing, we focus on the system performance metric of last finish time. In an upload-constrained P2P file sharing system, we study how to allocate the spare upload bandwidth and how to schedule data resource of assistant peers to improve the performance of P2P file distribution systems. We model both the equal service process and the differentiated service process when the initial data distribution of peers satisfies some special conditions, and also show how to minimize the time to get the file to any number of peers. The proposed fluid-based models can reveal the intrinsic relations among the initial data amount, the size of peer set and the minimum last finish time. The closed-form expressions derived from the extended models can closely approximate the chunk-based models and systems as well, especially for relatively large files. As an application of the extended models, we propose a recursive differentiated service strategy to provide differentiated service to multiple peer sets efficiently.Finally, with regard to the live streaming which has more advanced demands of real time, we concentrate on the system performance metrics of playout delay and playout probability. In a mesh-based overlay where peers have homogeneous upload bandwidth, we establish the analytic framework for the pull-based streaming schemes in P2P network, give accurate models of the chunk selection and peer selection strategies, and organize them into three categories, i.e., the chunk first scheme, the peer first scheme and the epidemic scheme. Moreover, we propose the LR2strategy, which incorporates a segmented chunk selection strategy and a random push strategy, then live streaming and file sharing can be optimized in a unified modeling framework.The results of this thesis have important theoretical and practical significance. On one hand, they could provide fundamental insights into bandwidth allocation and data scheduling in P2P content distribution; on the other hand, they could give helpful reference for improving system performance of P2P systems.