Design And Implementation Of P2P Content Distribution System Based On Network Coding

In the peer-to-peer (P2P) network, owning to the large number of computers are put together to share their CPU, storage and bandwidth resources, the more peers join in, the resources and service capabilities of entire P2P network are greater. Today, P2P content distribution system can distribute large files efficiently. However, traditional P2P content distribution system like Bittorrent has some problems such as strong dependency on seed nodes, uneven distribution of resources, and low resource utilization.In recent years, network coding is one of the most innovative technology of the field of information transmission. Based on network coding, intermediate nodes between the source and the receivers of a communication system no longer play the role of repeater, but encode the received data to forward. The original data were decoded at receivers. Recent studies show that the P2P content distribution system based on network coding can avoid the complicated and inefficient conetent negotiation and can ensure uniform distribution of resource and efficient distribution of files. This paper including:1) An intensive study of the structure of linear network coding and random linear network coding algorithm. An analysis of the implementation technologies of P2P content distribution system based on network coding, including complete code (Avanlanche) that is developed by Microsolft and rare code that can improve the encoding efficiency.2) Based on the study of the Bittorrent protocol, we design a P2P content distribution system based on network coding. Through modifying the Bittorrent protocol, we put forward four key designs:linear correlation detection, bitmap design, Interest mechanisms and Piece selection mechanisms.3) By means of open source software Enhanced CTorrent, we implement a network coding-based P2P file sharing client (NCTorrent) with C++.4) Finally, we test and annlysis the performance of NCTorrent and draw the following conclusions:First of all, the encoding efficiency of rare code is impressive to be able to meet the system requirements, and decoding efficiency is relatively low that may cause a certain impact of performance. Second, the efficiency of file distribution is closely related to file division and the advantage of network coding is less prominent in the small-scale network. At last, in file distribution system with large number of nodes, NCTorrent has higher system throughput and download success rate and is more resilient to dynamic nodes compared with BitTorrent, thus it achieves a higher efficiency of file distribution.