基于蚁群算法的非结构化P2P网络资源搜索策略

针对非结构化P2P网络资源搜索算法中冗余消息数过多、搜索效率低等问题,提出一种基于蚁群算法的非结构化P2P网络资源搜索策略,该策略利用蚂蚁信息素的正反馈原理,同时综合考虑邻居节点度和邻居-邻居节点信息,选择下一条邻居节点路径转发查询消息,有效地指导资源搜索路径的生成。实验结果表明,该算法在一定程度上减少了大量的冗余查询消息,提高了资源搜索的成功率,是一种有效的非结构化P2P网络资源搜索策略。     

OHQFS:一种非结构化P2P网络中数据查询搜索新策略

为了提高非结构化P2P网络中数据查询搜索的效率,提出一种新型的一跳查询与转发数据搜索新策略（OHQFS）,它是以非结构化P2P网络中的数据查询请求转发策略和非转发策略为基础,将它们整合、集成后得到的一种新策略.OHQFS策略中的查询源结点直接搜索其自身的所有邻居节点,并将查询请求转发给这些邻居节点,使得这些邻居节点再去搜索它们的相邻节点.该策略在数据查询搜索过程中无须维持一个很大的邻居节点信息集合,系统维护开销较小,通过本策略中固有的一步查询转发,使其邻居节点和邻居的邻居节点处于查询搜索范围内.网络仿真的实验结果表明,OHQFS策略相对于转发搜索策略而言,它提高了查询效率;而相对于非转发策略,它获得了较高的成功率.     

P2P资源智能查询策略的研究与设计

提高资源搜索效率、提高网络的扩展性一直是P2P网络的关键技术问题。在分析现有的P2P网络资源搜索的算法及其存在的问题的基础上,作者提出并设计了一种基于最近Query消息查询记录表、本地资源推荐路由表相结合的智能查询策略。能在保持原有搜索覆盖率的前提下,提高网络资源搜索效率,减少Query冗余信息,提高了网络的扩展性。     

一种改进的非结构化P2P网络资源搜索策略

非结构化P2P网络具有资源搜索效率不高,容易产生大量冗余信息等问题,为此,提出了一种改进的资源搜索策略。通过为网络中的节点建立朋友节点来改进传统的非结构化对等网络资源搜索,并在此基础上设计了一种新的资源搜索算法。仿真试验证明,该策略在一定程度上提高了非结构化P2P资源搜索的效率,同时减少了网络中的冗余信息量。     

非结构化P2P网络中减少冗余的搜索策略

在非结构化的P2P网络中,传统的洪泛式搜索造成大量的通信开销,严重制约了网络的可扩展性。根据标准洪泛机制在搜索的不同阶段表现出的不同特性,提出了一种基于TTL的分段搜索策略TTL-Search。TTL-Search把搜索过程分为两个阶段,各个阶段使用不同的策略转发消息。分析和实验结果表明,TTL-Search克服了洪泛搜索盲目性的特点,在一定程度上减少了查询带来的冗余开销,提高了查询成功率,能够高效地应用于非结构化P2P网络。     

一种有效的非结构化P2P网络资源搜索策略

针对非结构化P2P网络资源搜索算法中冗余消息数过多、搜索效率低等问题,提出了一种基于邻居-邻居节点的非结构化P2P网络资源搜索策略,该策略可以在一定程度上防止路由环路的产生,同时综合考虑邻居节点的活跃度和资源命中数,选择下一条邻居节点路径转发查询消息,将查询信息发往目标可能存在的区域,因此减少了发往网络的查询信息包数量,节省了网络带宽.实验结果表明,该算法可以减少大量的冗余查询信息,提高资源搜索的成功率,是一种有效的非结构化P2P网络资源搜索策略.     

P2P网络资源搜索方法研究

对等计算（P2P Computing）是下一代网络中的关键技术之一。如何高效地搜索P2P网络上的资源是P2P网络设计中最为关键的问题。文章介绍了P2P网络的特点及分类，在分析P2P网络的基本搜索方法的基础上，对各类搜索方法进行了分析和研究。     

在P2P网络中构建支持语义搜索的覆盖网络DOverlay

P2P网络上构建支持复杂语义请求的覆盖网络是一个新的挑战.支持复杂语义的覆盖网络不仅要满足P2P网络的完全分布性、动态性、可扩展性等相关特性,还要尽量提高P2P网络的可靠性和低成本维护性.提出的非结构化领域覆盖网络DOverlay由于其资源特征是直接由其对应领域本体的概念树转换而来,因此资源可自动形成相关聚类.而基于DOverlay的资源搜索策略D_Search不仅在减少了网络开销的前提下增大了搜索成功率,而且在Dl_Search中设计的资源评级策略还大大增加了搜索的有效性.     

基于特别兴趣组的P2P网络搜索算法

从实现搜索引擎的角度,分析了泛洪策略(flooding strategy), 扩展环策略(expending ring), 行走者(walker) 和多个行走者(k walker) 搜索策略。沿着这些策略的思路,引用“小世界”思想,进一步提出了基于特别兴趣组的P2P网路搜索查询算法。该算法的特点就是改变被动的提供信息网络节点为主动提供服务的网络节点,或者说把网络节点作用从信息提供者改变为查询向导。网络节点不但提供查询所求的内容,同时利用与它有相同兴趣的特别兴趣组通讯簿为所收到的查询提供指南。因此可以加快P2P网的查询速度,同时减轻网络负荷。     

反馈机制在P2P网络资源搜索中的应用研究

资源搜索是P2P网络的关键问题。目前P2P网络资源搜索中对反馈机制的应用研究较少,这样每次搜索对成功历史没有充分利用,搜索效率较低。该文针对此问题提出了基于改进的Rumormongering协议的资源发布算法BDFB(BidirectionFeedback),并将其应用到P2P网络资源搜索的反馈机制研究中,充分利用成功历史,提高资源在网络中的知名度,从而提高P2P网络中资源搜索效率。     

一种基于群组的P2P网络信任管理模型*

针对 P2P 网络中存在的多种恶意行为,提出一种基于群组的信任管理模型。该模型采用分组策略,引入直接信任度、组内信任度、组间信任度及多种控制因子来计算节点总体信任度,提高了信任机制的可靠性。仿真实验表明,该模型能够有效抑制多种恶意行为,提高系统成功交易率,使节点之间更有效地建立信任关系。     

基于模糊理论的P2P流媒体节点选择算法

传统Gossip协议对节点的选择存在盲目性,没有考虑节点的存储能力等影响因素,致使节点选择时网络搜索成功率较低,网络传输负载呈现出随机性。通过对非结构化P2P网络中广泛应用的Gossip协议进行探索和研究,运用模糊理论提出基于可靠性的节点选择策略。通过模拟实验对相关数据进行分析,结果表明该策略能有效提高P2P网络中节点的选择效率。     

低维护开销的小世界P2P网络

为降低结构化P2P网络的维护开销,提高路由和查询的效率,提出了具有低维护开销的小世界P2P网络（LMCS）,并描述了网络的创建和维护方法。小世界特征使结构化P2P网络具有较高的路由和查询效率,同时利用成簇机制和扩展COU策略,有效地降低网络的维护开销。通过模拟仿真,LMCS呈现明显的小世界网络特征。与Chord相比,LMCS具有更低的维护开销和更高的查询效率。     

Optimally designing caches to reduce P2P traffic

Traffic caused by P2P services dominates a large part of traffic on the Internet and imposes significant loads on the Internet, so reducing P2P traffic within networks is an important issue for ISPs. In particular, a huge amount of traffic is transferred within backbone networks; therefore reducing P2P traffic is important for transit ISPs to improve the efficiency of network resource usage and reduce network capital cost. To reduce P2P traffic, it is effective for ISPs to implement cache devices at some router ports and reduce the hop length of P2P flows by delivering the required content from caches. However, the design problem of cache locations and capacities has not been well investigated, although the effect of caches strongly depends on the cache locations and capacities. We propose an optimum design method of cache capacity and location for minimizing the total amount of P2P traffic based on dynamic programming, assuming that transit ISPs provide caches at transit links to access ISP networks. We apply the proposed design method to 31 actual ISP backbone networks and investigate the main factors determining cache efficiency. We also analyze the property of network structure in which deploying caches are effective in reducing P2P traffic for transit ISPs. We show that transit ISPs can reduce the P2P traffic within their networks by about 50-85% by optimally designing caches at the transit links to the lower networks.     

User density sensitive P2P streaming in wireless mesh networks

Link rate allocation is very important for supporting high video playback rate in Peer-to-Peer video streaming. Although many studies can be found on resource allocation in P2P streaming in wired networks, very few studies have studied the problem in wireless networks, especially in Wireless multi-hop Mesh Networks (WMNs), which is still challenging. To maximize the users’ satisfaction of P2P streaming in WMNs, this paper focuses on link rate allocation problem and proposes a fully distributed algorithm to efficiently utilize the upload and download bandwidth of wireless mesh nodes. We first build an efficient P2P streaming system based on the experimental results from real deployment of our wireless mesh testbed. Then we design an efficient distributed algorithm based on the solution to a linear optimization model, which optimizes towards a user-density-related objective to decide the best streaming rates among peers. Our scheme is resilient to network dynamics that is characteristic in wireless multi-hop peer-to-peer networks. The simulation experiments demonstrate the significant performance enhancement by using the proposed rate allocation algorithm in WMNs.     

一种面向数据抗毁性的对等网络数据存储策略*

现有评价机制不能准确评估结构化对等网络冗余存储策略,因此,引入数据抗毁性这一评价指标,从全复制、分块复制和有中心节点的分块复制三个角度对数据抗毁性进行建模分析。在此基础上,提出了一种基于动态中心确认机制的数据存储策略（DCDS）。实验证明,该策略在网络节点不断失效的情况下,对提高网络中可用数据的数量是有效的。     

融合网络异构P2P流媒体系统抗扰动性研究

融合网络中的异构P2P流媒体系统中具有多种终端、应用及节目类型,使得用户行为模式复杂,为系统稳定性带来了挑战。针对以上问题提出融合网络异构P2P流媒体系统稳定性增强策略。通过分析流媒体系统用户日志,确定用户行为影响因素,在此基础上对不同类型的用户行为进行收集及拟合,进行基于可靠性分析的路由、资源信息维护及合作节点选择,提高了系统资源信息维护准确性及节点间数据合作有效性。使用真实系统日志驱动的仿真实验验证了该策略的效果。     

An optimized strategy for update path selection in unstructured P2P networks

With the growth of P2P file sharing systems, people are no longer satisfied with the sharing of the read-only and static files, and thus the systems with mutually writable and dynamic files have emerged, resulting in the replica inconsistency problem. To maintain the replica consistency, too many update messages need to be redundantly propagated due to the lack of the sharing of globally updated path information in the existing strategies. To address this problem, we propose an optimized strategy for update path selection, which makes the nodes share the update path information by using clone, variation and crossover operations for the update paths. We also present a repeated update strategy to cope with the churn problem so as to maintain replica consistency as far as possible even if some nodes temporarily leave the network. The simulation results show that our strategy can significantly reduce the number of the redundant update messages without lowering the message coverage, thus improving the availability of the unstructured P2P networks.     

一种基于拥塞发现的强化学习P2P网络视频点播预取策略

在P2P(Peer to Peer)网络视频点播中设计合理的视频内容预取策略,可以有效地解决视频观看中出现的缓冲等待时间过长、服务器负载过大等问题。而现有的P2P网络视频预取方法往往考虑了视频内容的发现而忽略了节点本身的状态监控,在网络拥塞发生时存在视频播放观看不佳的情况。提出了一种基于拥塞发现的强化学习P2P网络视频点播预取策略,通过监测节点的拥塞状况以及带宽等参数,采用Q-learning学习算法综合评估网络节点,引导视频预取节点的选择,减少了对网络拥塞节点视频内容的预取。实验结果表明,该方法能提高视频播放流畅性,避免用户在节点发生拥塞时等待时间过长,提高了视频播放效率。     

Hybrid information retrieval policies based on cooperative cache in mobile P2P networks

The concept of Peer-to-Peer (P2P) has been introduced into mobile networks, which has led to the emergence of mobile P2P networks, and originated potential applications in many fields. However,mobile P2P networks are subject to the limitations of transmission range, and highly dynamic and unpredictable network topology, giving rise to many new challenges for efficient information retrieval. In this paper, we propose an automatic and economical hybrid information retrieval approach based on cooperative cache. In this method, the region covered by a mobile P2P network is partitioned into subregions, each of which is identified by a unique ID and known to all peers. All the subregions then constitute a mobile Kademlia (MKad) network. The proposed hybrid retrieval approach aims to utilize the floodingbased and Distributed Hash Table (DHT)-based schemes in MKad for indexing and searching according to the designed utility functions. To further facilitate information retrieval, we present an effective cache update method by considering all relevant factors. At the same time, the combination of two different methods for cache update is also introduced. One of them is pull based on time stamp including two different pulls: an on-demand pull and a periodical pull, and the other is a push strategy using update records. Furthermore, we provide detailed mathematical analysis on the cache hit ratio of our approach. Simulation experiments in NS-2 showed that the proposed approach is more accurate and efficient than the existing methods.