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Zu-Jie Ren 《计算机科学技术学报》2010,25(3):482-498
Recently, peer-to-peer (P2P) search technique has become popular in the Web as an alternative to centralized search due to
its high scalability and low deployment-cost. However, P2P search systems are known to suffer from the problem of peer dynamics,
such as frequent node join/leave and document changes, which cause serious performance degradation. This paper presents the
architecture of a P2P search system that supports full-text search in an overlay network with peer dynamics. This architecture,
namely HAPS, consists of two layers of peers. The upper layer is a DHT (distributed hash table) network interconnected by
some super peers (which we refer to as hubs). Each hub maintains distributed data structures called search directories, which could be used to guide the query and to control the search cost. The bottom layer consists of clusters of ordinary
peers (called providers), which can receive queries and return relevant results. Extensive experimental results indicate that HAPS can perform searches
effectively and efficiently. In addition, the performance comparison illustrates that HAPS outperforms a flat structured system
and a hierarchical unstructured system in the environment with peer dynamics. 相似文献
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网络测量是深入开展结构化对等网研究的基础,结构化对等网络协议设计、共享内容检索、态势感知乃至安全性的研究都需要以网络测量为前提.在节点分布对等、实时变化显著、未知瞬发扰动频繁的结构化对等网络中,获得其准确、完整的网络信息更是十分困难的.通过形式化分析结构化对等网节点搜索过程,研究节点信息在全网分布情况与查询返回率之间的关系,将历史测量数据与具体对等网特征信息相结合挖掘节点搜索优化策略,提出了一种网络资源占用显著降低、搜索速度较快、信息完备率较高的搜索测量优化方法.KAD 网络是目前得到大规模部署运行的为数不多的结构化对等网络之一,以KAD 网络为主要研究对象开发了KadCrawler 对等网搜索系统,进行了大量测量和分析,验证了搜索优化方法的可行性和有效性;同时,对当前KAD 网络拓扑结构特征、节点重名等现象进行了初步分析,发现KAD 网络近年来发生了显著的变化. 相似文献
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Internet的飞速发展使对等网络(P2P)及其相关领域的研究成为热点,但是当前P2P网络的结构并不完善。文中介绍了几种P2P模型,并在综合这几种模型优点的基础上,针对P2P网络的动态特性提出了一种分组P2P模型。该模型使用组节点管理对等点的加入和退出,有助于提高对等网络的稳定性。 相似文献
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High-throughput P2P streaming relies on peer selection, the strategy a peer uses to select other peer(s) as its parent(s)
of streaming. Although this problem has been thoroughly investigated in the classical optimization framework under static
settings, it still remains unaddressed as how to sustain throughput competitive to the optimum under highly dynamic peer churning.
To accommodate such peer dynamics, we extend the classical optimization framework and propose a distributed online peer selection
algorithm. This basic algorithm is further extended to a variety of settings commonly seen in operational P2P networks, such
as multi-parent streaming, admission control, delay constraint, etc. We prove approximation bound of our algorithm to the
optimal throughput. Through evaluation under different topological setups and peer churning sequences, we show that our solution
can consistently deliver competitive throughput, which greatly outperforms its theoretical bound.
This work was supported by NSF award 0643488, Vanderbilt Discovery grant, and a gift from Microsoft Research. Views and conclusions
of this paper are those of authors, which should not be interpreted as representing the official policies, either expressed
or implied, of the funding agencies. 相似文献
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《Multimedia, IEEE Transactions on》2009,11(3):509-522
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This paper proposes a two-level P2P caching strategy for Web search queries. The design is suitable for a fully distributed service platform based on managed peer boxes (set-top-box or DSL/cable modem) located at the edge of the network, where both boxes and access bandwidth to those boxes are controlled and managed by an ISP provider. Our solution significantly reduces user query traffic going outside of the ISP provider to get query results from the respective Web search engine. Web users are usually very reactive to worldwide events which cause highly dynamic query traffic patterns leading to load imbalance across peers. Our solution contains a strategy to quickly ease imbalance on peers and spread communication flow among participating peers. Each peer maintains a local result cache used to keep the answers for queries originated in the peer itself and queries for which the peer is responsible for by contacting the Web search engine on-demand. When query traffic is predominantly routed to a few responsible peers our strategy replicates the role of “being responsible for” to neighboring peers so that they can absorb query traffic. This is a fairly slow and adaptive process that we call mid-term load balancing. To achieve a short-term fair distribution of queries we introduce a location cache in each peer which keeps pointers to peers that have already requested the same queries in the recent past. This lets these peers share their query answers with newly requesting peers. This process is fast as these popular queries are usually cached in the first DHT hop of a requesting peer which quickly tends to redistribute load among more and more peers. 相似文献
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P2P打破传统的C/S模式,每个节点在网络中的地位都是对等的,既充当服务器,同时也共享其它服务。早期P2P网络仅考虑可用性,安全问题一直没有得到很好的解决。以下提出一种基于SSL协议的点对点通信架构,将安全套接字层SSL协议植入P2P网络,实现点对点安全通信,最后通过仿真实验和数据分析说明该实现方法的可行性。 相似文献
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基于P2P的个性化Web搜索系统的设计与实现 总被引:1,自引:0,他引:1
针对中心化的Web信息搜索系统在覆盖率、及时性、个性化、可扩展性等方面存在的问题,提出了一种基于Peer-to-Peer(P2P)的可扩展、个性化的Web搜索系统PeerBridge。PeerBridge基于分布式哈希表组织大量的网络结点形成有组织的P2P覆盖网络,每个对等体作为一个主题搜索引擎,根据用户兴趣从Web中搜索特定主题相关的信息,而具有相似主题的对等体被聚集在一起形成基于主题的对等体簇,协作进行Web搜索与信息共享。并采用主题驱动的Web爬行、基于语义概念的文档分类、个性化的链接分析和基于主题划分的P2P搜索等机制来改善PeerBridge的性能。 相似文献
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P2P网络具有良好的可扩展性和健壮性,但其匿名性、开放性等特征成为恶意行为的理想环境。针对上述问题,提出一种基于幂律分布的信誉评估机制识别网络中的良性行为,抵制恶意行为。仿真测试表明,运用该机制后计算节点信誉分值具有较小的计算开销和良好的准确度,支持节点的动态加入和退出,对于恶意节点的骚扰具有很强的健壮性。 相似文献
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This paper presents an efficient structured P2P overlay over MANET which better matches to the physical network in term of
routing. This feature is achieved by locally building up the minimum-spanning tree (MST) at each peer using the information
of the peer’s logical neighbors which are either directly connected (1-hop) or 2-hops away. Using this interconnection structure
among the peers, we design a new algorithm to distribute the contents information in the overlay by partitioning the identifier
(ID) space among the peers. In this algorithm, each peer maintains a disjoint portion of the ID space. The ID space at a peer
may be non-contiguous and each contiguous part is consecutive to the ID space of its directly connected neighbor peers. To
route the file-lookup query, each peer builds up a binary search tree (BST) using the knowledge of the ID space of itself
and of its directly connected neighbor peers. Simulation results show that our approach outperforms the existing approaches
in term of routing overhead, average file-discovery delay, false-negative ratio and average path-stretch value. 相似文献
17.
许松 《计算机工程与应用》2009,45(10):110-112
非结构化的P2P网络由于方便的全局部署和支持模糊匹配,而越来越受到欢迎,但是非结构化的P2P网络采用了洪泛的广播方式,因而导致网络的缩放性比较差,该文则在研究非结构化P2P网络拓扑结构存在问题的基础之上,提出采用平衡二叉树作为非结构化P2P网络的拓扑结构,设计相应的网络节点加入,节点退出,资源搜索等算法,并通过相应的仿真来展示改进的效果。 相似文献
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针对非结构P2P网络中搜索机制效率低下的问题,提出一种基于兴趣组的高效搜索模型。通过计算节点的相似性,得到兴趣节点,从而建立快捷链接,形成兴趣组。搜索请求首先在兴趣组中传播,提高了搜索效率。实验结果表明该模型对搜索请求具有较高的效率和准确性。 相似文献
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一种新型的层次P2P搜索模型 总被引:3,自引:0,他引:3
在分析现有P2P模型的基础上,提出了一种新的P2P搜索模型,该模型是分层的混合结构,利用分组和建立搜索空间的机制,来提高搜索的效率,增强系统的可扩展性。同时为低带宽节点引入了搜索代理的机制,提高了带宽的利用率,减少了搜索延迟。而且为了增强网络的自恢复性,利用缓存机制引入了备用连接,使搜索模型具有较好的容错能力。 相似文献
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Recent progress in peer to peer (P2P) search algorithms has presented viable structured and unstructured approaches for full-text search. We posit that these existing approaches are each best suited for different types of queries. We present PHIRST, the first system to facilitate effective full-text search within P2P databases. PHIRST works by effectively leveraging between the relative strengths of these approaches. Similar to structured approaches, agents first publish terms within their stored documents. However, frequent terms are quickly identified and not exhaustively stored, resulting in a significant reduction in the system's storage requirements. During query lookup, agents use unstructured search to compensate for the lack of fully published terms. Additionally, they explicitly weigh between the costs involved in structured and unstructured approaches, allowing for a significant reduction in query costs. Finally, we address how node failures can be effectively addressed through storing multiple copies of selected data. We evaluated the effectiveness of our approach using both real-world and artificial queries. We found that in most situations our approach yields near perfect recall. We discuss the limitations of our system, as well as possible compensatory strategies. 相似文献