文档介绍：摘要
近年来,随着移动终端设备的普及,将 P2P 技术应用到移动终端设备上(Mobile P2P) 成为一个热门的研究和应用领域。由于移动环境不同于有线网络(如节点的移动性、拓扑变化频繁等),传统的 P2P 资源发现算法并不能直接用于移动环境中。本文的主要研究是改进非结构化和结构化 P2P 网络下的传统资源发现算法,使之适用于移动环境。
首先,对于非结构化 P2P 网络下的资源发现算法,选取应用比较广泛的 flooding 算法作为研究对象。传统的 Flooding 算法的特点是需要进行大规模随机的网络遍历,这导致资源搜索开销很大。第三章中,基于 epidemic 的 flooding 算法(FBE)缓和了上述的遍历情况,在该算法中,资源提供者主动向移动网络中有选择的发布资源索引,并在资源索引的表结构中增加资源索引可信度(RIC,resource index confidence level)一项,使 flooding 算法在进行查询请求转发时可以根据 RIC 值进行有选择的转发。最后使用 NS2 进行仿真,仿真结果显示改进后的算法降低了延迟时间和网络负载,并且相比于传统的 flooding 算法,在资源搜索成功率上下降很小。
Chord 是结构化 P2P 网络中最流行性的一种资源搜索方案。第四章对 chord 的指针表进行重新设计,提高 chord 在移动环境下使用的搜索效率。改进方法为在指针表中增加逆时针指针项,使节点能够实现双向查询,并在指针表中增加了第二层后向节点。仿真结果表明,改进后的 chord 算法有效降低了资源查找过程中的平均路径长度。
关键词: 移动对等网络,资源索引,泛洪,Chord,指针表
Abstract
Recently, with the popularization of the mobile terminal devices, applying P2P on mobile terminals (mobile P2P) has e a hot research and application field. Since the mobile environment is different from wired (due to nodes’ mobility, and varying topology, etc.), the traditional P2P recourse discovery algorithm can not be directly used in the mobile environment. This thesis improved the traditional resource discovery algorithms in unstructured and structured works to adapt to the mobile environment.
Firstly, for resource discovery algorithm in unstructured work, this thesis chose the well-known flooding as study object. Traditional flooding search algorithm needs to iterate through the work, which leads to the high overhead in searching resource. In chapter 3, flooding based epidemic (FBE) is introduced to alleviate the above weakpoint. Specifically, each resource provider actively diffuses resource index to mobile work. And furthermore, an item called RIC (resource index confidence level) is added to the index table. Flooding with RIC can forward the query selectively. Simulations have been taken with NS2 and the results of simulations show that the improved flooding algorithm can decrease time delay work load, and the ess rate of searching reso