A distributed resource discovery algorithm for P2P grids

Centralized or hierarchical administration of the classical grid resource discovery approaches is unable to efficiently manage the highly dynamic large-scale grid environments. Peer-to-peer (P2P) overlay represents a dynamic, scalable, and decentralized prospect of the grids. Structured P2P methods do not fully support the multi-attribute range queries and unstructured P2P resource discovery methods suffer from the network-wide broadcast storm problem. In this paper, a decentralized learning automata-based resource discovery algorithm is proposed for large-scale P2P grids. The proposed method supports the multi-attribute range queries and forwards the resource queries through the shortest path ending at the grid peers more likely having the requested resource. Several simulation experiments are conducted to show the efficiency of the proposed algorithm. Numerical results reveal the superiority of the proposed model over the other methods in terms of the average hop count, average hit ratio, and control message overhead.     

P2P-based resource discovery in dynamic grids allowing multi-attribute and range queries

A key point for the efficient use of large grid systems is the discovery of resources, and this task becomes more complicated as the size of the system grows up. In this case, large amounts of information on the available resources must be stored and kept up-to-date along the system so that it can be queried by users to find resources meeting specific requirements (e.g. a given operating system or available memory). Thus, three tasks must be performed, (1) information on resources must be gathered and processed, (2) such processed information has to be disseminated over the system, and (3) upon users’ requests, the system must be able to discover resources meeting some requirements using the processed information. This paper presents a new technique for the discovery of resources in grids which can be used in the case of multi-attribute (e.g. {OS = Linux & memory = 4 GB}) and range queries (e.g. {50 GB < disk-space < 100 GB}). This technique relies on the use of content summarisation techniques to perform the first task mentioned before and strives at the main drawback found in proposals from literature using summarization. This drawback is related to scalability, and is tackled by means of using Peer-to-Peer (P2P) techniques, namely Routing Indices (RIs), to perform the second and third tasks.Another contribution of this work is a performance evaluation conducted by means of simulations of the EU DataGRID Testbed which shows the usefulness of this approach compared to other proposals from literature. More specifically, the technique presented in this paper improves on the scalability and produces good performance. Besides, the parameters involved in the summary creation have been tuned and the most suitable values for the presented test case have been found.     

Mesh-connected trees: a bridge between grids and meshes of trees

The grid and the mesh of trees (or MOT) are among the best-known parallel architectures in the literature. Both of them enjoy efficient VLSI layouts, simplicity of topology, and a large number of parallel algorithms that can efficiently execute on them. One drawback of these architectures is that algorithms that perform best on one of them do not perform very well on the other. Thus there is a gap between the algorithmic capabilities of these two architectures. We propose a new class of parallel architectures, called the mesh-connected trees (or MCT) that can execute grid algorithms as efficiently as the grid, and MOT algorithms as efficiently as the MOT, up to a constant amount of slowdown. In particular, the MCT topology contains the MOT as a subgraph and emulates the grid via embedding with dilation 3 and congestion two. This significant amount of computational versatility offered by the MCT comes at no additional VLSI area cost over these earlier networks. Many topological, routing, and embedding properties analyzed here suggest that the MCT architecture is also a serious competitor for the hypercube. In fact, while the MCT is much simpler and cheaper than the hypercube, for all the algorithms we developed, the running time complexity on the MCT matches those of well known hypercube algorithms. We also present an interesting variant of the MCT architecture that admits both the MOT and the torus as its subgraphs. While most of the discussion in this paper is focused on the MCT architecture itself, these analyses can be easily extended to the variant of the MCT presented here     

P2P与网格相似性研究

网格和P2P都属于分布式技术,它们最初产生的原因不同,但总体目标相似。本文对P2P与网格技术的相似性与差异性进行了研究,重点对比分析了它们的资源管理机制、安全机制、容错机制以及连通性等几个关系系统性能的重要方面。通过对P2P模式与网格模式的对比分析,找出它们各自的优势与不足之处,以便综合利用它们的技术优势来构建高性能的分布式系统。     

P2P与网格的互补性研究

P2P与网格都是新型的分布式计算模型,它们的总体目标相似,对P2P和网格模型中的安全性、连通性、访问服务、资源发现与管理、容错以及协同性等几个重要问题进行分析,为将P2P模型中的技术应用到网格中来创造条件。采用P2P协议和模型来处理网格计算,并利用P2P与网格技术之间的协同和互补来构建高性能的分布式系统,从而增加网格的可扩展性,实现非分层的分散网格系统。     

P2PSimulator:一个通用P2P协议模拟器

点对点(Peer-to-Peer,P2P)技术作为分布式系统领域的一个新的热门技术,已经取得众多的研究成果。但是预想中的标准性基础构架系统并没有出现,研究者们设计了多种不同的协议,在不同的环境下进行试验,使得各个协议之间难以进行公平的对比评价。该文从自身的需要出发,设计并实现了一个通用的P2P协议模拟器P2PSimulator,一个跨平台、高效、支持蒙特卡罗方法、支持多种协议、高度可配置的通用模拟器框架,希望能够改变这种状况。     

A simple efficient algorithm for interpolation between different grids in both 2D and 3D

Considering the importance of data transferring between different grids, we present a simple but powerful interpolation scheme using radial basis functions (RBFs) to accomplish such task in both 2D and 3D. Numerical results are presented for such interpolation between truly unstructured grids.     

P2P data replication and trustworthiness for a JXTA-Overlay P2P system using fuzzy logic

P2P systems are very important for future distributed systems and applications. In such systems, the computational burden of the system can be distributed to peer nodes of the system. Therefore, in decentralized systems users become themselves actors by sharing, contributing and controlling the resources of the system. This characteristic makes P2P systems very interesting for the development of decentralized applications. Data replication techniques are commonplace in P2P systems. Data replication means storing copies of the same data at multiple peers thus improving availability and scalability. The trustworthiness of peers also is very important for safe communication in P2P system. The trustworthiness of a peer can be evaluated based on the reputation and actual behaviour of peers to provide services to other peers. In this paper, we propose two fuzzy-based systems for data replication and peer trustworthiness for JXTA-Overlay P2P platform. The simulation results have shown that in the first system, replication factor increases proportionally with increase of number of documents per peer, replication percentage and scale of replication per peer parameters and the second system can be used successfully to select the most reliable peer candidate to execute the tasks.     

Building and Querying a P2P Virtual World

Peer-to-Peer (P2P) systems are known to provide excellent scalability in a networked environment. One peer is introduced to the system by each participant. However current P2P applications can only provide file sharing and other forms of relatively simple data communications, and, in this paper, we demonstrate how this limitation can be bridged by indexing and querying a 3D virtual-world on a dynamic distributed network. We present an algorithm for 3D range queries as well as an algorithm for nearest neighbor queries. We also show how to build such a complex application from the ground level of a P2P routing algorithm.     

2-dimensional implicit hydrodynamics on adaptive grids

We present a numerical scheme for two-dimensional hydrodynamics computations using a 2D adaptive grid together with an implicit discretization. The combination of these techniques has offered favorable numerical properties applicable to a variety of one-dimensional astrophysical problems which motivated us to generalize this approach for two-dimensional applications. Due to the different topological nature of 2D grids compared to 1D problems, grid adaptivity has to avoid severe grid distortions which necessitates additional smoothing parameters to be included into the formulation of a 2D adaptive grid. The concept of adaptivity is described in detail and several test computations demonstrate the effectivity of smoothing. The coupled solution of this grid equation together with the equations of hydrodynamics is illustrated by computation of a 2D shock tube problem.     

P2P技术原理与应用软件

P2P的对等结构是互联网本质的回归,以P2P技术为支撑的网络应用目前席卷了整个网络产业。诸如BitTorrent、Thunder、Skype,P2P应用已成为当前网络技术领域的一颗明星。本文介绍了P2P技术基本原理和基于P2P技术的主流软件。     

P2P技术原理与应用软件

P2P的对等结构是互联网本质的回归，以P2P技术为支撑的网络应用目前席卷了整个网络产业。诸如BitTorrent、Thunder、Skype，P2P应用已成为当前网络技术领域的一颗明星。本文介绍了P2P社术基本原理和基于P2P技术的主流软件。     

一种新型P2P Botnet的分析与检测

Botnet是一种新型网络攻击方式,它为攻击者提供了灵活高效的命令与控制机制,对Internet安全造成了巨大的威胁。该文概要介绍了Botnet技术,分析了基于P2P技术的Botnet的特点,并对一种新型P2P Botnet进行了深入的分析和研究,提出了对新型P2P Botnet的检测方法。     

Toward mutual dependency between empathy and technology

Technology explosion induced by information explosion will eventually change artifacts into intelligent autonomous agents consisting of surrogates and mediators from which humans can receive services without special training. Four potential problems might arise as a result of the paradigm shift: technology abuse, responsibility flaw, moral in crisis, and overdependence on artifacts. Although the first and second might be resolved in principle by introduction of public mediators, the rest seems beyond technical solution. Under the circumstances, a reasonable goal might be to create a mutual dependency between empathy and technology: Using technology to help people cultivate empathy among people, so empathy in the society may allow people to help each other to recover from disasters beyond the scope of the assumption underlying the society of mediators. I highlight an immersive collaborative interaction environment for helping people share first-person view and its application to building empathic agents.     

一种对等网络负载平衡算法的研究

对等网络正在成为网络应用研究的一个新的热点,负载平衡技术是其中的一个重要问题。该文提出了一种基于局部负载扩散思想的对等网络负载平衡算法,对相应的负载评估标准、负载分散原则等内容进行了详细描述,最后给出了仿真试验结果。试验数据表明,该算法具有较低的系统开销、较小的响应延迟,减少了系统抖动现象的产生。     

Defending a P2P digital preservation system

The LOCKSS (Lots Of Copies Keep Stuff Safe) system allows users to store and preserve electronic content through a system of inexpensive computers arranged in an ad hoc peer-to-peer network. These peers cooperate to detect and repair damage by voting in "opinion polls." We develop a more accurate view of how the network will perform over time by simulating the system's behavior using dynamic models in which peers can be subverted and repaired. These models take into account a variety of parameters, including the rate of peer subversion, the rate of repair, the extent of subversion, and the responsiveness of each peer's system administrator. These models reveal certain systemic vulnerabilities not apparent in our static simulations: a typical adversary that begins with a small foothold within the system (e.g., 20 percent of the population) will completely dominate the voting process within 10 years, even if he only exploits one vulnerability each year. In light of these results, we propose and evaluate countermeasures. One technique, ripple healing, performs remarkably well. For models in which all system administrators are equally likely to repair their systems, it eliminates nearly systemic levels of corruption within days. For models in which some administrators are more likely to repair their systems, ripple healing limits corruption, but proves less effective, since these models already demonstrate superior performance     

The interface between computers and psychology: Toward a psychology of computerization

The computer has made itself felt virtually everywhere in modern life, including psychology. In fact, the literature that is concerned with computer-related issues indicates that there are four areas where the computing and psychological sciences have come to interact with each other on a consistent basis. The major dimensions of this computer-psychology interface are: artificial intelligence, human-computer interaction, clinical/educational applications, and the question of the impact of computers on human identity. A phenomenology of the computer-related psychological literature indicates that each of these four areas includes a specific group of core issues, key research studies, and leading authors. This article describes the major issue that characterizes each dimension of the computer-psychology interface, and argues that it is time for psychology to formally recognize the importance of this emerging psychology of computerization.     

P2P技术分析与流量管理研究

随着P2P应用的日益流行,P2P流量消耗了网络的大量带宽,已经影响到了互联网传统业务的服务质量。为解决这一问题,网络运营者和研究人员在P2P流量的管理技术上进行了大量的探索研发工作,主要有P2P流量阻塞、缓存和本地化疏导等技术。首先对P2P技术做了简单概述,然后分析了影响P2P流量分布的重要技术因素,之后综述了最新的P2P流量管理技术,最后做了总结。     

Providing security and fault tolerance in P2P connections between clouds for mHealth services

The mobile health (mHealth) and electronic health (eHealth) systems are useful to maintain a correct administration of health information and services. However, it is mandatory to ensure a secure data transmission and in case of a node failure, the system should not fall down. This fact is important because several vital systems could depend on this infrastructure. On the other hand, a cloud does not have infinite computational and storage resources in its infrastructure or would not provide all type of services. For this reason, it is important to establish an interrelation between clouds using communication protocols in order to provide scalability, efficiency, higher service availability and flexibility which allow the use of services, computing and storage resources of other clouds. In this paper, we propose the architecture and its secure protocol that allows exchanging information, data, services, computing and storage resources between all interconnected mHealth clouds. The system is based on a hierarchic architecture of two layers composed by nodes with different roles. The routing algorithm used to establish the connectivity between the nodes is the shortest path first (SPF), but it can be easily changed by any other one. Our architecture is highly scalable and allows adding new nodes and mHealth clouds easily, while it tries to maintain the load of the cloud balanced. Our protocol design includes node discovery, authentication and fault tolerance. We show the protocol operation and the secure system design. Finally we provide the performance results in a controlled test bench.     

一种混合P2P网络模型研究与设计

当前主流P2P网络模型存在的可扩展性不高,效率低下以及对电信主干网负荷太大等问题已经严重阻碍了P2P应用的发展。虽然结构化P2P网络模型在一定程度上解决了这些问题,但其本身存在的缺陷也使其很难转化成实用系统。在分析以上网络优缺点的基础上,提出一种基于混合模式的新型P2P网络模型,并对新模型的实现方式和重要过程进行详细描述。在此基础上进一步引入管理机制和新型关键值匹配方案以增强网络的管理型和实用性。