基于对等网络的流媒体点播系统的研究与实现

提出了一个基于对等网络的流媒体点播系统Stream on Peer（SoP）的设计与实现。首先概述了SoP系统的网络拓扑和系统结构,之后讨论了系统中节点登录与退出、数据源解析、流媒体数据分块、数据块调度算法等关键技术,最后提供了实验数据并讨论了进一步的工作。     

P2P分布式存储系统

设计了一个基于P2P的分布式存储系统.该存储系统采用高可扩展的P2P体系结构,将大量分散的节点组织成一个逻辑网络,充分利用原先被忽视的端系统资源,构建大规模分布式存储系统.该存储系统采用高效的结构化P2P路由机制、动态自适应的副本管理、信任机制和激励机制为用户提供高效、可靠的分布式存储服务.     

基于邻近度的P2P路由算法

邻近度路由技术对P2P网络的路由性能影响很大.本文提出一种新的分布式结构化P2P路由算法FDPNS.FD-PNS路由算法采用邻近度路由技术,节点在转发一个查询请求后触发路由表的维护任务,有针对性地对本次转发使用的路由表项进行优化,以减小搜索和定位的路由延迟,提高系统的整体性能.     

ORN: A content-based approach to improving supplier discovery in P2P VOD networks

There are two major building blocks in operating a peer-to-peer (P2P) video-on-demand (VOD) network: supplier discovery and content delivery. Supplier discovery concerns the discovery of peer nodes in the network that can provide the streaming data blocks needed for playing by a local node. The more suppliers one can discover, the higher the chance of locating quality suppliers for delivering contents smoothly to ensure uninterrupted playback. The key to supplier discovery is to establish and track the supply-demand relationship among the peers. For P2P VOD, the supply-demand relationship is determined by the buffer contents of the peers. Unfortunately, the buffer contents change rapidly as peers play the video, especially under VCR operations. The challenge is to track all the dynamic relationships in an efficient way. In this paper, we propose an Overlapping Relation Network (ORN). The idea is to track the dynamic supply-demand relationship by tracking the overlapping of peers’ buffer contents. As long as peers play the video at the same rate, the overlapping relationship is stable and can be used for low-cost supplier discovery. Extensive analyses and simulation experiments show that in most cases the ORN can discover more than 96% of the suppliers in the network, resulting in a streaming continuity that is superior to that of other approaches.     

A distributed data clustering algorithm in P2P networks

Clustering is one of the important data mining issues, especially for large and distributed data analysis. Distributed computing environments such as Peer-to-Peer (P2P) networks involve separated/scattered data sources, distributed among the peers. According to unpredictable growth and dynamic nature of P2P networks, data of peers are constantly changing. Due to the high volume of computing and communications and privacy concerns, processing of these types of data should be applied in a distributed way and without central management. Today, most applications of P2P systems focus on unstructured P2P systems. In unstructured P2P networks, spreading gossip is a simple and efficient method of communication, which can adapt to dynamic conditions in these networks. Recently, some algorithms with different pros and cons have been proposed for data clustering in P2P networks. In this paper, by combining a novel method for extracting the representative data, a gossip-based protocol and a new centralized clustering method, a Gossip Based Distributed Clustering algorithm for P2P networks called GBDC-P2P is proposed. The GBDC-P2P algorithm is suitable for data clustering in unstructured P2P networks and it adapts to the dynamic conditions of these networks. In the GBDC-P2P algorithm, peers perform data clustering operation with a distributed approach only through communications with their neighbours. The GBDC-P2P does not need to rely on a central server and it performs asynchronously. Evaluation results demonstrate the superior performance of the GBDC-P2P algorithm. Also, a comparative analysis with other well-established methods illustrates the efficiency of the proposed method.     

结构化P2P系统路由机制的研究

基于分布式哈希表的结构化P2P系统得到了广泛的研究,这些系统的网络拓扑结构一般都以图论中的一些广为研究的图作基础,而且大量借鉴了并行系统的研究成果。介绍了几个常见的结构化P2P系统,对其拓扑结构和路由算法作了分析对比。     

结构化P2P路由协议的改进

在P2P系统中,为高效地定位资源节点,提高系统性能,在分析经典Chord算法的基础上,通过扩展Chord路由表,提出一种新的路由算法,该算法能够减少转发次数,缩短搜索路径的长度及搜索延迟。仿真实验结果表明,该算法继承了经典Chord算法简单、高效、可靠、负载平衡及开销少的优点,提高Chord的查找效率。     

基于信任管理的对等网络路由选择

在对等网络中每个节点都充当了路由的作用,在搜索某文件时,正确地选择转发节点,可提高搜索文件的效率。构建了基于信任的动态拓扑模型,给出了节点信任度评估的方法;提出了用加密发送消息的方法,确定故障节点;通过设定CPU的响应时间阈值,解决高可信节点因被链接过多而导致的节点拥塞,避免对高可信节点的完全依赖;设计了基于信任的节点链接更新算法,提高了网络性能。通过仿真实验验证了该方法的正确性。     

基于反馈相关性的P2P网络信任模型

用户对P2P网络安全性的需求刺激了信任模型的发展。在分析现有信任模型的基础上,提出了基于反馈相关性的动态信任模型—CoDyTrust。其在时间帧的基础上,采用虚假信任过滤机制和信任聚合机制,并在信任值计算中引入信任相关系数、信任遗忘因子、滥用信任值和推荐信任度等,通过反馈控制机制动态调节这些模型因子,在准确评价节点对不同资源信任的同时,实现网络中恶意行为检测。比较分析结果表明,CoDyTrust能够更好地反映网络中节点行为,准确检测恶意节点,有效抵御振荡、撒谎和合谋等攻击。     

基于语义路由的P2P信息检索

高效、稳定的P2P信息检索机制已经成为了研究的热点。现有的搜索方法包括使用广播方式或者分布式哈希表。基于分布式哈希表的方法虽然可以获得很好的查询性能,但是不支持近似查询,区间查询、而使用广播方式效率又低,引入语义路由,能很好地解决这些问题。语义路由是一种对广播搜索进行修剪的方法,将查询请求有选择的发送给能响应请求的节点。论文中介绍了语义路由机制,提出了基于该机制的P2P检索系统体系结构,最后使用NeuroGrid进行了仿真,实验结果显示使用语义路由可以提高查询效率。     

一种基于分区的移动P2P网络路由算法

校园内无线网络的普遍使用与移动设备性能的快速发展,使移动P2P技术得到了更多的关注。但当前对移动对等网络的研究还缺乏统一而明确的定义,还存在很多未能很好地解决的问题。文中的研究目的是如何有效组织移动节点,进行资源交换。针对校园无线网络环境,提出了一种基于分区模型的移动P2P网络结构。对节点历史行为统计,计算节点性能值。并利用分区网络模型和机会路由的思想提出了一种改进路由算法,实现区域内和区域间路由转发,降低了路由开销,提高了网络性能。     

结构化P2P路由表分析与改进

在结构化P2P搜索算法中,chord算法是最为典型的。但该算法的fingertable中信息有冗余,同时转发次数比较多,因而效率不高。通过分析chord算法、fingertable结构,对冗余的信息进行删除,并对已搜索过的资源的后向节点进行保存而减少转发次数。通过理论分析,该算法提高了chord的查找效率。     

一种改进的P2P网络业务路由算法

业务路由是研究如何在覆盖网络环境下提供有Qos保证的复合业务的问题.针对目前的业务路由算法扩展性差、业务路由不稳定等特点,提出了一种大规模P2P网络环境下的分布式业务路由改进算法-LBLD.对系统内的所有业务节点按其地理位置进行分簇形成一种层次化的拓扑结构,通过簇首之间汇总信息的传递减少了节点之间传输报文的信息量,改善了算法的可扩展性.同时在选择业务路径中的节点主机时,考虑了主机的生命周期,使最终采用的业务路径具有较好的稳定性,减少了由于节点异常离开而造成业务中断的概率.模拟实验证明了这种算法的有效性.     

Context-based caching and routing for P2P web service discovery

In modern heterogeneous environments, such as mobile, pervasive and ad-hoc networks, architectures based on web services offer an attractive solution for effective communication and inter-operation. In such dynamic and rapidly evolving environments, efficient web service discovery is an important task. Usually this task is based on the input/output parameters or other functional attributes, however this does not guarantee the validity or successful utilization of retrieved web services. Instead, non-functional attributes, such as device power features, computational resources and connectivity status, that characterize the context of both service providers and consumers play an important role to the quality and usability of discovery results. In this paper we introduce context-awareness in web service discovery, enabling the provision of the most appropriate services at the right location and time. We focus on context-based caching and routing for improving web service discovery in a mobile peer-to-peer environment. We conducted a thorough experimental study, using our prototype implementation based on the JXTA framework, while simulations are employed for testing the scalability of the approach. We illustrate the advantages that this approach offers, both by evaluating the context-based cache performance and by comparing the efficiency of location-based routing to broadcast-based approaches. Recommended by: Zakaria Maamar     

Semantic routing of search queries in P2P networks

Peer-to-peer (P2P) networks are beginning to form the infrastructure of future applications. Heavy network traffic limits the scalability of P2P networks. Indexing is a method to reduce this traffic. But indexes tend to become large with the growth of the network. Also, limiting the size of these indexes causes loss of indexing information. In this paper we introduce a novel ontology based index (OI) which limits the size of the indexes without sacrificing indexing information. We show that the method can be employed by many P2P networks. The OI sits on top of routing and maintenance modules of a P2P network and enhances it. The OI prunes branches of search trees which have no chance to proceed to a response. Also the OI guarantees that an enhanced routing algorithm and its basic version have the same result set for a given search query. This means that the OI reduces traffic without reducing quality of service. To measure the performance of the OI we apply it on Chord (DHT based) and HyperCup (non-DHT based) P2P networks and show that it reduces the networks’ traffic significantly.     

P2P文件共享系统中基于访问控制的信任模型

在P2P文件共享系统中,节点之间共享彼此的文件.但是由于对等网络的匿名性和开放性,在文件共享系统中存在很多信任方面的问题,如恶意节点和自私节点的大量存在.为了孤立恶意节点和鼓励节点共享自己的文件,提出了基于访问控制的信任模型.首先,定义了一种信任机制,它引入了直接信任,推荐信任,时间衰减等因子.其次,对每个共享文件都加入了两个阈值--可信性总评价阈值和贡献量阈值来控制访问.对于每个请求者,只有当它有了对文件的访问资格后才能访问该文件.最后,通过大量的实验证明了本模型的可行性和高效性,特别是对恶意节点具有很好的孤立作用.     

结构化P2P网络上可靠的基于内容路由协议

在结构化P2P网络上构建基于内容的发布/订阅系统,可以很好地支持大规模、高度动态的分布式应用.然而,现有的基于内容的路由协议在P2P网络上只能提供弱的可靠性保证.根据结构化P2P网络的路由协议的特点,设计了一种新型的基于内容的路由协议--基于编码区间的路由(identifier range based routing,简称IRBR)协议.IRBR协议具有良好的容错性,只要事件的发布者与订阅者之间在P2P网络中是可达的,则订阅者一定能够收到它所订阅的事件,且只收到一次.同时,该协议也比现有的协议具有更高的事件路由效率.在Pastry上开发了一个原型系统,模拟实验表明了该协议的效率和容错性.     

优化的多媒体流多播选路的试探算法

在网络实时应用如远程教育、视频会议等系统中,对多播多媒体流的每一个流,不仅有严格的端到端时延限制,还有网络带宽的约束。网络在满足应用服务请求的同时,还应尽可能地降低资源的消耗。因此需要研究优化网络资源利用的多媒体流多播路由算法。论文采用优化的试探方法解决多播路由多媒体流分发问题。实验结果表明优化后的算法,与已有算法比较起来,使客户端接收视频流的满意度提高5%～8%,链路带宽节余8%～20%。     

基于Bloom Filter路由表的P2P搜索算法

研究非结构化P2P网络的搜索机制,提出基于布莱姆过滤器(BF)路由表的改进算法。该算法利用BF技术生成路由条目并在一定范围内相互交换本地路由表,使节点能够了解一定范围内的节点共享信息,实现有针对性的搜索,避免传统的盲目性搜索。仿真结果表明,该算法查询搜索时产生的消息数量比传统算法减少一个数量级,并能够获得较好的查全率。     

基于语义的p2p路由算法研究综述

路由算法在P2P网路中占有重要的地位,资源的定位、查找均依赖于高效的路由算法。传统的P2P网络采用分布式哈希表来进行路由,是与资源的自然语义内容无关的算法,或者说分布式哈希表破坏了自然语言的语义内容。最近10年以来,语义路由算法在P2P网络中逐渐兴起。随着语义网的提出,本体成为自然语言研究方面的热点。语义覆盖网正是基于本体的知识体系构建的。而随着社交网路的兴起,又提出了语义小世界的概念。LSI、LSH、VSM以及各中聚类算法均在P2P网络的语义路由中得到了广泛的应用。