基于BitTorrent的文件分发策略关键技术研究

【作者】 杨文君；

【导师】 何兴高；

【作者基本信息】 电子科技大学 ， 信息与通信工程， 2010， 硕士

【摘要】 目前P2P技术在多个领域中取得了广泛的应用,BitTorrent是典型的基于P2P技术的文件分发系统,拥有广泛的用户群。本文以改善BitTorrent的分发性能,提高系统文件下载时间,加快文件分发时间为研究目的,其主要创新如下:(1)提出了基于Tracker算法优化的节点选择策略。该策略中,Tracker服务器在统计在线节点时,对在线节点的上传速率、下载速率、节点状态作了分类并排序,当有节点请求邻居节点时,Tracker根据节点在网络中所处的下载时期这个特征,从排序的上传速率、下载速率链表里选取部分节点作为请求节点的邻居节点。(2)提出了基于空闲带宽的内容分发策略。本文在分析新入网节点、即将下载完成的节点的工作原理的基础上,指出新入网节点下载前期存在着空闲的下载带宽,而处于下载后期阶段的节点存在着空闲的上传带宽。针对这个问题,基于空闲带宽的内容分发策略对其做了优化:当检测到节点处于这两种状态时,分别通过自适应增加其下载带宽、上传带宽,来有效整合其闲置资源,以提高系统资源利用率,并在整体性能上节省了文件分发时间。(3)提出了基于稀有分片的内容分发策略。在阐述文件分片均匀分布重要性时,本文提出了通过种子节点来调节文件分片分布。基于稀有分片的内容分发策略在此思想的基础上,对种子节点的工作机制做了优化:种子节点统计周围邻居节点各自拥有的文件分片,计算出稀有分片,优先把网络中稀有分片分发给新入网节点,以平衡稀有分片的数目。该策略与基于Tracker算法优化的节点选择策略相辅相成。此三种策略的相互协作,极大地加快了BitTorrent分发文件的效率,使得在相同规模的网络环境下,BitTorrent能更快的分发相同大小的文件。这种文件分发效率的提高,具有很强的现实背景和应用价值。之后,本文介绍了基于分布式对等网络仿真平台的策略仿真设计,并经仿真测试证实了优化策略的预期效果。更多还原

【Abstract】 Peer-to-Peer (P2P) technology has achieved a wide range of applications. As one of the P2P file distribution system, BitTorrent has become the hotspot of P2P study. This thesis aimed at decreasing file download time in order to improve BitTorrent distribution performance. The main research of this thesis is as follows:Firstly, an optimized node selection strategy was proposed to overcome the drawbacks of random node selection in BitTorrent systems: Tracker server classified online nodes useful information, which included the upload, download, and node state. When there was node requesting neighbor list, tracker selected the neighbor nodes by the request node’s period partially from the statistical results, partially from the random results. It was worth noting the seed nodes, which will work on the optimized strategy introduced later, if it was contained in the returned neighbor nodes.Secondly, this thesis pointed out that there existed unoccupied bandwidth, which was download bandwidth at the node’s initial stage, while upload bandwidth at the last stage of nodes. In response to this, an optimized content distribution strategy was proposed: When node was at the initial or last stage, it will adaptively increase its unoccupied bandwidth in order to effectively integrate the idle resources and improve the system performance.Thirdly, according to seed character, this thesis proposed that the seed node can regulate the piece distribution. To avoid the negative effects of rare piece, the seed node’s operating mechanism was optimized: seed node will stat. pieces amount which were owned by neighbor nodes, then calculate the rare pieces, so it can balance the amount of rare pieces by giving priority to the nodes which requests the rare pieces.Based on distributed simulation platform, this thesis designed and implemented these optimized strategies. Simulation results demonstrated that optimal strategies achieved better distributed efficiency while retaining the architecture of BitTorrent.更多还原