一种基于兴趣协助的P2P网络共享文件搜索方法

分析了传统的结构化P2P网络和非结构化P2P网络搜索方法的优点和缺点,提出了一种基于兴趣协助的搜索方法,通过在结构化P2P网络节点上发布兴趣来加速非结构化P2P网络上的查询。实验结果表明,此方法在查询成功率和搜索延迟等方面都有着较好的性能。     

主题重叠网络的构造与搜索算法研究

结构化P2P网络虽然具有扩展性良好的数据查找机制,但只支持基于键的准确匹配搜索.为提供更丰富的数据查询能力,本文提出一种基于主题重叠网络的结构化P2P搜索算法--主题重叠网络搜索算法(TONS).其基本思想是在结构化P2P网络之上,将结点按主题组织成分层的重叠网络,使含有相似主题的结点相互链接在一起;利用主题中继结点所具有的全局导航能力,TONS能够基于内容将查询限定在P2P网络的局部范围内,并且通过在重叠网络中随机添加一些长距离链接,使重叠网络具有Small-World特性,改善TONS的搜索性能.实验结果表明,TONS大大提高了搜索的查全率,减少了P2P网络信息搜索时的平均路径距离和平均消息数目.     

SemreX: Efficient search in a semantic overlay for literature retrieval

The World Wide Web is growing at such a pace that even the biggest centralized search engines are able to index only a small part of the available documents on the Internet. The decentralized structure, together with the features of self-organization and fault-tolerance, makes peer-to-peer networking an effective information-sharing model; however, content searching still remains a serious challenge of large scale peer-to-peer networks. In this paper we present SemreX, a semantic overlay for desktop literature/ document retrieval in peer-to-peer networks. We present a semantic overlay algorithm by which semantically similar peers are locally clustered together, and long-range connections are rewired for a short-cut in peer-to-peer networks. Based on the semantic overlay, a heuristic query routing algorithm is proposed for efficient content searching. We conduct a comprehensive simulation to evaluate the search performance of our algorithms. Results show that search in our SemreX semantic overlay greatly improves search efficiency.     

Assisted Peer-to-Peer Search with Partial Indexing

In the past few years, peer-to-peer (P2P) networks have become a promising paradigm for building a wide variety of distributed systems and applications. The most popular P2P application till today is file sharing, e.g., Gnutella, Kazza, etc. These systems are usually referred to as unstructured, and search in unstructured P2P networks usually involves flooding or random walking. On the other hand, in structured P2P networks (DHTs), search is usually performed by looking up a distributed inverted index. The efficiency of the search mechanism is the key to the scalability of a P2P content sharing system. So far, neither unstructured nor structured P2P networks alone can solve the search problem in a satisfactory way. In this paper, we propose to combine the strengths of both unstructured and structured P2P networks to achieve more efficient search. Specifically, we propose to enhance search in unstructured P2P overlay networks by building a partial index of shared data using a structured P2P network. The index maintains two types of information: the top interests of peers and globally unpopular data, both characterized by data properties. The proposed search protocol, assisted search with partial indexing, makes use of the index to improve search in three ways: first, the index assists peers to find other peers with similar interests and the unstructured search overlay is formed to reflect peer interests. Second, the index also provides search hints for those data difficult to locate by exploring peer interest locality, and these hints can be used for second-chance search. Third, the index helps to locate unpopular data items. Experiments based on a P2P file sharing trace show that the assisted search with a lightweight partial indexing service can significantly improve the success rate in locating data than Gnutella and a hit-rate-based protocol in unstructured P2P systems, while incurring low search latency and overheads.     

一种基于多重覆盖的结构化P2P搜索

本文提出了一种基于多重覆盖的结构化P2P搜索策略,mDOS(multi-Dimensional Overlays based Search).mDOS模拟社会网络中的小世界模型,根据结点的多重属性将结点组织成为多维树型结构.每一维上的任意两个结点根据其在树型结构中的位置形成语义距离.按照覆盖网络中实际距离与语义距离之间的一定函数关系构造多重覆盖网络.邻居结点和目标结点之间在网络中的实际距离可以通过他们的语义距离估计得到,形成基于结点属性的路由方向感.两个结点的有效距离取值多维中的最短语义距离.多重覆盖中的一个结点可以桥接在不同维上的邻居结点,缩小结点之间的平均有效距离,进而缩短搜索路径长度.mDOS还引入索引内容"懒惰维护"机制和路由表"被动修改"机制以克服结点动态性带来的覆盖网络维护代价.最后的实验表明mDOS可以降低搜索路径长度,降低维护代价,提高可用性.     

Enabling Dynamic Querying over Distributed Hash Tables

Dynamic querying (DQ) is a search technique used in unstructured peer-to-peer (P2P) networks to minimize the number of nodes that is necessary to visit to reach the desired number of results. In this paper, we introduce the use of the DQ technique in structured P2P networks. In particular, we present a P2P search algorithm, named DQ-DHT (Dynamic Querying over a Distributed Hash Table), to perform DQ-like searches over DHT-based overlays. The aim of DQ-DHT is twofold: allowing arbitrary queries to be performed in structured P2P networks and providing dynamic adaptation of the search according to the popularity of the resources to be located. DQ-DHT has been particularly designed for use in those distributed environments, like computational grids, where it is necessary to support arbitrary queries for searching resources on the basis of complex criteria or semantic features. This paper describes the DQ-DHT algorithm using Chord as basic overlay and analyzes its performance in comparison with DQ in unstructured networks.     

Tree-Based Index Overlay in Hybrid Peer-to-Peer Systems

Hybrid Peer-to-Peer(P2P) systems that construct overlay networks structured among superpeers have great potential in that they can give the benefits such as scalability,search speed and network traffic,taking advantages of superpeer-based and the structured P2P systems.In this article,we enhance keyword search in hybrid P2P systems by constructing a tree-based index overlay among directory nodes that maintain indices,according to the load and popularity of a keyword.The mathematical analysis shows that t...     

SSON：一种基于结构化P2P网络路由的语义覆盖网络结构

本文基于结构化P2P网络路由机制,采用基于主题划分的方法,提出了基于结构化P2P网络路由的语义覆盖网络SSON。SSON通过结构化P2P网络的标识符映射机制,根据资源类别将结点组织成层次化的覆盖网络,该覆盖网络结构确保搜索限制在与查询主题相关的局部结点子集中。该结构充分利用了结构化P2P网络的优点,解决了基于非结构化P2P网络建立的语义覆盖网络的对主题群的搜索低效问题,同时克服了结构化P2P网络仅支持精确匹配查找的缺点,为结构化P2P网络提供了可靠、高效的语义查询机制,极大地提高了查全率。     

基于P2P的结构化半分布式语义搜索算法

目前的搜索引擎算法大多是基于关键词搜索,体系上是集中式结构,在安全性和语义性上存在缺陷.基于P2P的结构化半分布式语义搜索算法--DPSS(Distributed P2P Semantic Search),通过研究词与词的关联度,在传统的P2P覆盖语义层,实现语义功能.同时,结合文章距离算法,能够应用在文本分类、文章聚类等领域.     

Fuzzynet: Ringless routing in a ring-like structured overlay

Many structured overlay networks rely on a ring invariant as a core network connectivity element. The responsibility ranges of the participating peers and navigability principles (greedy routing) heavily depend on the ring structure. For correctness guarantees, each node needs to eagerly maintain its immediate neighboring links - the ring invariant. However, the ring maintenance is an expensive task and it may not even be possible to maintain the ring invariant continuously under high churn, particularly as the network size grows. Furthermore, routing anomalies in the network, peers behind firewalls and Network Address Translators (NATs) create non-transitivity effects, which inevitably lead to the violation of the ring invariant. We argue that reliance on the ring structure is a serious impediment for real life deployment and scalability of structured overlays. In this paper we propose an overlay called Fuzzynet, which does not rely on the ring invariant, yet has all the functionalities of structured overlays. Fuzzynet takes the idea of lazy overlay maintenance further by dropping any explicit connectivity and data maintenance requirement, relying merely on the actions performed when new Fuzzynet peers join the network. We show that with sufficient amount of neighbors (O(log N), comparable to traditional structured over-lays), even under high churn, data can be retrieved in Fuzzynet w.h.p. We validate our novel design principles by simulations as well as PlanetLab experiments and compare them with ring based overlays.     

Overlay construction for mobile peer-to-peer video broadcasting

An efficient overlay is a crucial component of wireless cooperative live video streaming networks—an emerging wireless streaming solution with ever-increasing storage and computation capabilities, and provides scalability, autonomy, carrier-billing network bandwidth conservation, service coverage extension, etc. Based on whether routes are pre-calculated and maintained, or determined per-hop in reactive to each data piece, the streaming overlay can be classified as either unstructured, structured, or hybrid. We discuss issues, properties and example approaches of each category in detail, and present quantitative and qualitative comparisons on their strengths and weaknesses in terms of system robustness, overlay maintenance complexity, delivery ratio, end-to-end delay, etc. Finally we discuss some open issues and emerging areas regarding overlay construction.     

Overlay networks: A scalable alternative for P2P

Overlay networks create a structured virtual topology above the basic transport protocol level that facilitates deterministic search and guarantees convergence. Overlay networks are evolving into a critical component for self-organizing systems. Here we outline the differences between flooding-style and overlay networks, and offer specific examples of how researchers are applying the latter to problems requiring high-speed, self-organizing network topologies.     

一种结构化P2P网络拓扑匹配的通用算法

与非结构化P2P网络相比,结构化P2P网络具有良好的可扩展性、鲁棒性。但是结构化P2P覆盖网络是直接建立在逻辑网络之上,没有过多地考虑底层物理网络拓扑结构,导致逻辑拓扑结构与物理拓扑结构严重不匹配。本文提出一种新的协议无关的拓扑匹配算法,将现有的界标节点、自适应匹配算法与IP分配策略相结合构建初始拓扑结构,优化节点交换算法来维护拓扑结构。模拟实验表明,本算法提高了网络的拓扑匹配度,具有更低的通信开销。     

Repeatable and reliable semantic search evaluation

An increasing amount of structured data on the Web has attracted industry attention and renewed research interest in what is collectively referred to as semantic search. These solutions exploit the explicit semantics captured in structured data such as RDF for enhancing document representation and retrieval, or for finding answers by directly searching over the data. These data have been used for different tasks and a wide range of corresponding semantic search solutions have been proposed in the past. However, it has been widely recognized that a standardized setting to evaluate and analyze the current state-of-the-art in semantic search is needed to monitor and stimulate further progress in the field. In this paper, we present an evaluation framework for semantic search, analyze the framework with regard to repeatability and reliability, and report on our experiences on applying it in the Semantic Search Challenge 2010 and 2011.     

Laurel:一种混合式数据分发覆盖网

覆盖网是各种数据分发应用的基础架构.在节点波动的网络环境中实现快速而准确的数据分发,对覆盖网提出了两个要求:高效的数据路由;较强的系统鲁棒性.已有的覆盖网构建方法多侧重于某个方面的优化,因而未能充分权衡数据路由效率与系统鲁棒性.提出了一种混合式数据分发覆盖网--Laurel.Laurel通过簇间多重结构化拓扑与簇内非结...     

基于Hilbert曲线的双层覆盖网模型

资源定位和负栽均衡是P2P网络系统中急需解决的核心问题。本文给出的模型将连续相邻的结点组成一个无结构的结点组,结点组之间利用Chord协议连接成为一个全局结构化的环形拓扑结构,并在该拓扑结构中引入HBLS资源查找算法和动态负载均衡双层环状模型调度策略。整个方案不仅具有很好的负载平衡特性,而且为查找提供了充分的灵活性性。仿真实验表明,该模型在资源定位和负载平衡两个方面都优于原Chord。     

Socially aware microcloud service overlay optimization in community networks

Community networks are a growing network cooperation effort by citizens to build and maintain Internet infrastructure in regions that are not available. Adding that, to bring cloud services to community networks (CNs), microclouds were started as an edge cloud computing model where members cooperate using resources. Therefore, enhancing routing for services in CNs is an attractive paradigm that benefits the infrastructure. The problem is the growing consumption of resources for disseminating messages in the CN environment. This is because the services that build their overlay networks are oblivious to the underlying workload patterns that arise from social cooperation in CNs. In this paper, we propose Select in Community Networks (SELECTinCN), which enhances the overlay creation for pub/sub systems over peer-to-peer (P2P) networks. Moreover, SELECTinCN includes social information based on cooperation within CNs by exploiting the social aspects of the community of practice. Our work organizes the peers in a ring topology and provides an adaptive P2P connection establishment algorithm, where each peer identifies the number of connections needed based on the social structure and user availability. This allows us to propagate messages using a reduced number of hops, thus providing an efficient heuristic to an NP-hard problem that maps the workload graph to the structured P2P overlays resulting in a number of messages close to the theoretical minimum. Experiments show that, by using social network information, SELECTinCN reduces the number of relay nodes by up to 89% using the community of practice information versus the state-of-the-art pub/sub notification systems given as baseline.     

基于分散网坐标的P2P搜索算法

对结构化P2P网络模型Chord的搜索算法进行讨论,指出其优点和不足.对于其搜索算法中存在的覆盖网络和底层网络不一致而带来的查询延时问题,本文结合Chord在拓扑结构和数据分布等方面的特点,以分散网坐标为基础,提出了基于分散网坐标的搜索算法,使搜索向着延迟相对小的节点进行.实验证明,基于分散网坐标的搜索算法使查询的路由跳数更少,路由延迟更小,查询效率也更高.     

语义覆盖网最佳规模的数学分析

现在大量研究者通过语义覆盖网构建来提高P2P网络资源查询效率,但在语义覆盖网最佳规模大小上缺乏研究。考虑运用数学方法对语义覆盖网络进行数据建模,对路由算法的路由性能指标的求解方法进行研究,并分析语义覆盖网规模与路由性能指标之间的关系。通过模型的分析和求解,得出了社区的最佳规模大小,为语义覆盖网构建与研究提供了有力的支撑。