E-ARL: An Economic incentive scheme for Adaptive Revenue-Load-based dynamic replication of data in Mobile-P2P networks

In mobile ad hoc peer-to-peer (M-P2P) networks, frequent network partitioning occurs due to peer movement or owing to peers switching ‘off’ their mobile devices. This leads to typically low data availability in M-P2P networks, thereby necessitating data replication. This work proposes E-ARL, which is a novel Economic scheme for Adaptive Revenue-Load-based dynamic replication of data in dedicated M-P2P networks with the aim of improving data availability. Thus, E-ARL considers a mobile cooperative environment, where the MPs are working towards the same goal, and the network performance is facilitated by the economic scheme. E-ARL essentially allocates replicas based on its economic scheme. Each data item has a price in virtual currency. E-ARL requires a query issuing peer to pay the price of its queried data item to the query-serving peer and a commission to relay peers in the successful query path. The main contributions of E-ARL follow. First, it uses an economic scheme for efficiently managing M-P2P resources in a context-aware manner by facilitating effective replica hosting and message relaying by peers. Second, it collaboratively performs bid-based replica allocation to facilitate better quality of service. Third, it incorporates both revenue-balancing and load-balancing to improve peer participation and performance. Fourth, it conserves the energy of low-energy MPs to facilitate network connectivity. Our performance evaluation shows that E-ARL is indeed effective in improving peer participation in M-P2P networks, thereby improving query response times, query success rates, query hop-counts and replica allocation traffic.     

基于对等组的P2P安全通信机制

当前对P2P网络系统安全的研究大多着眼于构造信任和名誉模型,而对通信过程的安全问题研究较少。提出了一种基于对等组实现的P2P安全通信机制——P2PSCM。P2PSCM首先为通信节点构建安全对等组。组内节点相互通信时,先通过交换公私密钥和对称密钥建立节点间安全通信渠道;然后采用对称密钥加密传输数据;最后对接收数据进行身份确认与完整性验证,确保相互间安全通信。     

P2P环境下数据管理系统上的Top-k查询

目前大多数P2P系统只提供文件的共享,缺乏数据管理能力.基于关系数据库上的关键搜索,本文提出了一种在P2P环境下共享数据库的新框架,其中每个节点上的数据库被看成是一个文档集,用户不用考虑数据库的模式结构信念,简化了不同节点数据库模式间的映射过程,能更好地适应P2P的分散和动态特性.将基于直方图的分层Top-k查询算法扩展到P2P环境下的数据库管理系统上,文档集和数据库的查询被统一起来,一致对待.在查询处理期间,直方图可以自动更新,同时根据查询结果,邻居节点可以自调整,具有自适应性.实验结果表明,基于关键词的数据库共享突破了传统的数据库共享模式,简化了数据访问方式,而基于直方图的Top-k查询算法提高了查询效率.     

Efficient resource discovery in self‐organized unstructured peer‐to‐peer networks

In unstructured peer‐to‐peer (P2P) networks, two autonomous peer nodes can be connected if users in those nodes are interested in each other's data. Owing to the similarity between P2P networks and social networks, where peer nodes can be regarded as people and connections can be regarded as relationships, social strategies are useful for improving the performance of resource discovery by self‐organizing autonomous peers on unstructured P2P networks. In this paper, we present an efficient social‐like peer‐to‐peer (ESLP) method for resource discovery by mimicking different human behaviours in social networks. ESLP has been simulated in a dynamic environment with a growing number of peer nodes. From the simulation results and analysis, ESLP achieved better performance than current methods. Copyright © 2008 John Wiley & Sons, Ltd.     

An economic incentive model for encouraging peer collaboration in mobile-P2P networks with support for constraint queries

In mobile ad hoc peer-to-peer (M-P2P) networks, economic models become a necessity for enticing non-cooperative mobile peers to provide service. M-P2P users may issue queries with varying constraints on query response time, data quality of results and trustworthiness of the data source. Hence, we propose ConQuer, which is an economic incentive model for the efficient processing of constraint queries in M-P2P networks. ConQuer also provides incentives for peer collaboration in order to improve data availability. The main contributions of ConQuer are three-fold. First, it uses a broker-based economic M-P2P model for processing constraint queries via a Vickrey auction mechanism. Second, it proposes the CR*-tree, a dynamic multidimensional R-tree-based index for constraints of data quality, trust and price of data to determine target peers efficiently. The CR*-tree is hosted by brokers, who can sell it to other peers, thereby encouraging the creation of multiple copies of the index for facilitating routing. Third, it provides incentives for peers to form collaborative peer groups for maximizing data availability and revenues by mutually allocating and deallocating data items using royalty-based revenue-sharing. Such reallocations facilitate better data quality, thereby further increasing peer revenues. Our performance study shows that ConQuer is indeed effective in answering constraint queries with improved response time, success rate and data quality, and querying hop-counts.

Performance evaluations of data-centric information retrieval schemes for DTNs

Mobile nodes in some challenging network scenarios, e.g. battlefield and disaster recovery scenarios, suffer from intermittent connectivity and frequent partitions. Disruption Tolerant Network (DTN) technologies are designed to enable communications in such environments. Several DTN routing schemes have been proposed. However, not much work has been done on designing schemes that provide efficient information access in such challenging network scenarios. In this paper, we explore how a content-based information retrieval system can be designed for DTNs. There are three important design issues, namely (a) how data should be replicated and stored at multiple nodes, (b) how a query is disseminated in sparsely connected networks, and (c) how a query response is routed back to the issuing node. We first describe how to select nodes for storing the replicated copies of data items. We consider the random and the intelligent caching schemes. In the random caching scheme, nodes that are encountered first by a data-generating node are selected to cache the extra copies while in the intelligent caching scheme, nodes that can potentially meet more nodes, e.g. faster nodes, are selected to cache the extra data copies. The number of replicated data copies K can be the same for all data items or varied depending on the access frequencies of the data items. In this work, we consider fixed, proportional and square-root replication schemes. Then, we describe two query dissemination schemes: (a) W-copy Selective Query Spraying (WSS) scheme and (b) L-hop Neighborhood Spraying (LNS) scheme. In the WSS scheme, nodes that can move faster are selected to cache the queries while in the LNS scheme, nodes that are within L-hops of a querying node will cache the queries. For message routing, we use an enhanced Prophet scheme where a next-hop node is selected only if its predicted delivery probability to the destination is higher than a certain threshold. We conduct extensive simulation studies to evaluate different combinations of the replication and query dissemination algorithms. Our results reveal that the scheme that performs the best is the one that uses the WSS scheme combined with binary spread of replicated data copies. The WSS scheme can achieve a higher query success ratio when compared to a scheme that does not use any data and query replication. Furthermore, the square-root and proportional replication schemes provide higher query success ratio than the fixed copy approach with varying node density. In addition, the intelligent caching approach can further improve the query success ratio by 5.3–15.8% with varying node density. Our results using different mobility models reveal that the query success ratio degrades at most 7.3% when the Community-Based model is used compared to the Random Waypoint (RWP) model [J. Broch et al., A Performance Comparison of Multihop wireless Ad hoc Network Routing Protocols, ACM Mobicom, 1998, pp. 85–97]. Compared to the RWP and the Community-Based mobility models, the UmassBusNet model from the DieselNet project [X. Zhang et al., Modeling of a Bus-based Disruption Tolerant Network Trace, Proceedings of ACM Mobihoc, 2007.] achieves much lower query success ratio because of the longer inter-node encounter time.     

Top-<Emphasis Type="Italic">k</Emphasis> query processing in mobile-P2P networks using economic incentive schemes

This work proposes the E-Top system for the efficient processing of top-k queries in mobile ad hoc peer to peer (M-P2P) networks using economic incentive schemes. In E-Top, brokers facilitate top-k query processing in lieu of a commission. E-Top issues economic rewards to the mobile peers, which send relevant data items (i.e., those that contribute to the top-k query result), and penalizes peers otherwise, thereby optimizing the communication traffic. Peers use the payoffs (rewards/penalties) as a means of feedback to re-evaluate the scores of their items for re-ranking purposes. The main contributions of E-Top are three-fold. First, it proposes two economic incentive schemes, namely ETK and ETK+, in which peers act individually towards top-k query processing. Second, it extends ETK and ETK+ to propose a peer group-based economic incentive scheme ETG. Third, our performance evaluation shows that our schemes are indeed effective in improving the performance of top-k queries in terms of query response times and accuracy at reasonable communication traffic cost.     

纯Peer to Peer环境下有效的Top-k查询

目前大多数的Peer-to-Peer(P2P)系统只支持基于文件标识的搜索,用户不能根据文件的内容进行搜索.Top-k查询被广泛地应用于搜索引擎中,获得了巨大的成功.可是,由于P2P系统是一个动态的、分散的系统,在纯的P2P环境下进行top-k查询是具有挑战性的.提出了一种基于直方图的分层top-k查询算法.首先,采用层次化的方法实现分布式的top-k查询,将结果的合并和排序分散到P2P网络中的各个节点上,充分利用了网络中的资源.其次,根据节点返回的结果为节点构建直方图,利用直方图估计节点可能的分数上限,对节点进行选择,提高了查询效率.实验证明,top-k查询提高了查询效果,而直方图则提高了查询效率.     

数据网格环境下一种动态自适应的副本定位方法

在数据网格中，数据常常会由于性能和可用性等原因进行复制，如何有效地定位数据的一个或多个副本的物理位置是数据网格系统需要解决的重要问题，提出了一种可扩展、动态自适应的分布副本定位方法——DSRL，DSRL使用宿主结点来支持对同一数据多个副本的同时高效定位，使用本地副本定位结点来支持对副本的本地查询。DSRL提出了一种动态均衡映射方法，将全局副本定位信息均衡分布在多个宿主结点上，并且能够自适应宿主结点的动态加人或退出，详细描述了DSRL的组成，并对DSRL方法的正确性和负载平衡等特性进行了证明，分析和实验表明，DSRL方法有着良好的可扩展性、可靠性、自适应性和性能，并且实现简单，有着较好的实用性。     

提高P2P下top-k搜索性能的研究

分析了P2P中节点资源分布特点。根据搜索条件,在资源匹配度的基础上提出了节点匹配度的概念。基于节点匹配度与资源的smallworld分布特征提出top-k资源的搜索、评价算法。该算法使搜索能够在整个网络内进行,并朝资源匹配高的范围传播。在提高搜索效率、节约网络带宽的同时,保证了最终获取的k个资源是最匹配的。根据搜索条件选择广播匹配节点的方法有效地平衡了搜索、评价的带宽和计算资源。     

高P2P下top-k搜索性能的研究*

分析了P2P中节点资源分布特点。根据搜索条件,在资源匹配度的基础上提出了节点匹配度的概念。基于节点匹配度与资源的small world分布特征提出top-k资源的搜索、评价算法。该算法使搜索能够在整个网络内进行,并朝资源匹配高的范围传播。在提高搜索效率、节约网络带宽的同时,保证了最终获取的k个资源是最匹配的。根据搜索条件选择广播匹配节点的方法有效地平衡了搜索、评价的带宽和计算资源。     

P2P网中基于文件分片的副本建立策略

在大规模P2P网络中,为了提高数据的可用性,可以通过在系统中多个节点上建立数据副本的方法来增加数据的冗余度.传统方法建立副本的过程中,数据资源通常是以完整的数据文件为单位在节点间进行拷贝.为了减小副本建立的开销,可采用一种基于文件分片的副本建立策略,将需要复制的数据文件先进行分片,然后把这些分片在一组选取好的候选节点间进行分发复制,能够充分利用网络带宽,明显减小建立副本所需的时间开销.     

移动环境中一种基于Hash的P2P覆盖网

目前提出的大多数基于哈希（hash—based）的P2P网络都集中于固定的对等节点。当节点移动到网络中一个新的位置时,这种结构在消息传递等方面的效率就会下降。文章提出一种移动环境中的基于哈希的P2P覆盖网（Hash—based P2P Overlay in Mobile Environment,H—MP2P）,允许节点在网络中自由移动。一个节点可通过P2P网络广播其位置信息,其他节点通过网络可以获知该节点的移动信息并进行定位。通过理论分析和实验可知H—MP2P在扩展性、可靠性和效率方面都可以取得较好的结果,可以很好的应用在移动环境中。     

A New Protocol for the Detection of Node Replication Attacks in Mobile Wireless Sensor Networks

Wireless sensor networks (WSNs) are often deployed in harsh environments.Thus adversaries can capture some nodes,replicate them and deploy those replicas back into the strategic positions in the network to launch a variety of attacks.These are referred to as node replication attacks.Some methods of defending against node replication attacks have been proposed,yet they are not very suitable for the mobile wireless sensor networks.In this paper,we propose a new protocol to detect the replicas in mobile WSNs.In this protocol,polynomial-based pair-wise key pre-distribution scheme and Counting Bloom Filters are used to guarantee that the replicas can never lie about their real identifiers and collect the number of pair-wise keys established by each sensor node.Replicas are detected by looking at whether the number of pair-wise keys established by them exceeds the threshold.We also derive accurate closed form expression for the expected number of pair-wise keys established by each node,under commonly used random waypoint model.Analyses and simulations verify that the protocol accurately detects the replicas in the mobile WSNs and supports their removal.     

Pathfinder: Visual Analysis of Paths in Graphs

The analysis of paths in graphs is highly relevant in many domains. Typically, path‐related tasks are performed in node‐link layouts. Unfortunately, graph layouts often do not scale to the size of many real world networks. Also, many networks are multivariate, i.e., contain rich attribute sets associated with the nodes and edges. These attributes are often critical in judging paths, but directly visualizing attributes in a graph layout exacerbates the scalability problem. In this paper, we present visual analysis solutions dedicated to path‐related tasks in large and highly multivariate graphs. We show that by focusing on paths, we can address the scalability problem of multivariate graph visualization, equipping analysts with a powerful tool to explore large graphs. We introduce Pathfinder, a technique that provides visual methods to query paths, while considering various constraints. The resulting set of paths is visualized in both a ranked list and as a node‐link diagram. For the paths in the list, we display rich attribute data associated with nodes and edges, and the node‐link diagram provides topological context. The paths can be ranked based on topological properties, such as path length or average node degree, and scores derived from attribute data. Pathfinder is designed to scale to graphs with tens of thousands of nodes and edges by employing strategies such as incremental query results. We demonstrate Pathfinder's fitness for use in scenarios with data from a coauthor network and biological pathways.     

?无结构P2P网络中的混合式搜索方法

针对轻洪泛冗余查询消息数多、对稀有资源搜索延迟大的问题,提出一种结合无结构P2P搜索技术和双向Chord环的混合式搜索方法。该方法利用节点的异构性,在k-walker随机走的基础上,根据邻居节点的查询能力,对查询请求的转发方式进行改进,在双向Chord环中对无结构P2P未搜索到的资源进行结构化P2P搜索。仿真结果证明,与轻洪泛相比,混合式搜索方法的冗余查询消息数较少,对稀有资源的搜索延迟较小。     

基于可信对等的分布式入侵检测通信框架设计

为了提高分布式入侵检测的实时性和安全性,提出了一种可信对等的分布式入侵检测通信框架的模型.该模型借鉴了P2P和代理技术,不同网络节点中的入侵检测代理是对等的,它们之间通过共享检测信息进行整体协防.该模型还借鉴了安全通信技术,在网络中建立了一个认证服务器,不在同一网络节点的任何两个网络进程的通信必须通过该认证服务器,提高了入侵检测自身的安全性.设计实现了一个原型系统,原型系统的实验结果表明了该模型的正确性和可行性.     

IVDQP—物联网内基于兴趣向量的分布式查询处理方法

物联网内资源按需检索是构建高效率物联网应用的必备功能。实现一种基于兴趣的数据单播查询处理方法IVDQP,采用一种单播的方式对任意物联网节点提出的数据检索请求进行节点间传递,并以一种累积的方式将中间节点上的检索结果按照查询单播传递路径返回给查询节点。与Flooding算法的对比实验表明,提出的这种物联网内单播查询处理方法不仅能够迅速定位尽可能多的符合查询要求的数据,而且能够保证引入尽可能少的节点间的消息交换,从而为高效物联网应用的实现提供技术支持。     

一种实现高效副本发布与查询的DHT覆盖网

在对等计算应用中,副本复制技术是提升查询命中率、提升查询速度、维护负载均衡的一种有效方法,然而它也提升了在存储空间和流量上的代价.研究如何在结构化的P2P覆盖网中,通过拓扑优化手段减少复制中的冗余流量和冗余副本.首先在网络中选择支配集节点作为超级节点,设计一个层次化的、体现节点邻近度的P2P覆盖网,然后基于多hash函数,开发对应的复制技术以实现低代价的副本查询.该方法能够有效地在网络中分散副本,提升查询命中率,减少冗余消息和所需存储空间.给出了性能指标的理论分析,并通过仿真验证了该方法的优越性.     

Managing peer-to-peer networks with human tactics in social interactions

Small-world phenomena have been observed in existing peer-to-peer (P2P) networks which has proved useful in the design of P2P file-sharing systems. Most studies of constructing small world behaviours on P2P are based on the concept of clustering peer nodes into groups, communities or clusters. However, managing additional multilayer topology increases maintenance overhead, especially in highly dynamic environments. In this paper, we present Social-like P2P systems (Social-P2Ps) for object discovery by self-managing P2P topology with human tactics in social networks. In Social-P2Ps, queries are routed intelligently even with limited cached knowledge and node connections. Unlike community-based P2P file-sharing systems, we do not intend to create and maintain peer groups or communities consciously. In contrast, each node connects to other peer nodes with the same interests spontaneously by the result of daily searches.