The Doomsday distributed termination detection protocol

Distributed termination detection (DTD) algorithms are important since they detect globally stable states in distributed computations. Here we introduce a new DTD mechanism, the Doomsday protocol together with its proof of correctness. Doomsday is generic since it forms the basis for a number of new and existing DTD algorithms for which the correctness proof may be reused. The paper describes the Doomsday protocol, provides its formal proof, derives one new DTD algorithm and shows how other hitherto unrelated algorithms, Dijkstra–Scholten, Task Balancing and Credit Recovery, can be derived from the protocol. The paper concludes by examining various properties of the protocol in the context of existing DTD algorithms. This work was supported in part by Visiting Fellowship grant EPSRC GR/R84481/01 “The Doomsday Protocol” and by Australian Research Council ARC Linkage International Grant LX0349049 “Extending a Family of Garbage Collectors”.     

Algorithms for distributed termination detection

The termination problem for distributed computations is analyzed in the general context of asynchronous communication. In the underlying computational model it is assumed that messages take an arbitrary but finite time and do not necessarily obey the FIFO rule. Time diagrams are used as a graphic means of representing the overall communication scheme, giving a clear insight into the difficulties involved (e.g., lack of global state or time, inconsistent time cuts) and suggesting possible solutions.Several efficient algorithms for the solution of the termination problem are presented. They are all based on the idea of message counting but have a number of different characteristics. The methods are discussed and compared with other known solutions.Friedemann Matternreceived the Diploma in computer science from the University of Bonn, West Germany, in 1983.He is now a research scientist in the Department of Computer Science at the University of Kaiserslautern and is currently completing his Ph.D. His primary research interests include distributed algorithms, programming language design, and compiler construction. The author can be reached by electronic mail via mattern @ incas.uucp or mattern % uklirb.uucp @ Germany.csne.This work has been supported by the Deutsche Forschungsgemeinschaft (DFG) as part of the SFB124 research project VLSI-Design and Parallelism     

Termination detection for distributed computations

A simple derivation of a general solution to the problem of detecting the termination of a distributed computation is presented.     

全零块预判的运动估计及模式选择早结束研究

针对全零DCT（Discrete Cosine Transform）系数块,为避免对其进行变换和量化操作以减少编码器的运算量,基于全零块预判的本质,根据DCT系数分布的特性,结合H.264/AVC整数变换和量化的特点,提出了一种预先判断全零DCT系数块的新方法。同时,针对H.264/AVC高精度运动矢量和多编码模式的高复杂度,通过分析最佳匹配块搜索的本质,提出了基于全零DCT系数块预判准的运动估计和模式选择早结束算法。实验结果表明,与已有基于全零块准则的快速运动估计算法相比,其实际搜索点数均有较明显的减少。     

周期终止探测算法研究

在分布式环境中,周期性通信是安全节点间进行信息交换的主要方式。〖BP）〗针对以管理域为单元的集中式通信方案,提出了利用通信子树进行周期终止探测的算法。通过向各安全节点分配连续的、唯一的节点标识,并将标识嵌入到消息中,该算法可以利用求和公式实现通信终止判定。该算法简单而有效,算法复杂度达到最优。     

An efficient parallel termination detection algorithm

In this paper, we present a new, easy to implement algorithm for detecting the termination of a parallel asynchronous computation on distributed-memory MIMD computers. We demonstrate that it operates concurrently with the main computation, adding minimal overhead, and we prove that it correctly detects termination when it occurs. Experimental results confirm that the termination detection routine imposes an overhead smaller than the experimental uncertainty.     

分布式检测系统的一种软决策融合算法

在分布式检测系统中,为了进一步提高系统的性能,各传感器可以向融合中心发送多位二进制判决信息.对于这种发送多位判决信息的软决策融合系统,提出了一种对各传感器观测空间进行再划分的方法,它将各传感器的观测空间按照其检测概率和虚警概率进行再划分.这种划分方法能够简化融合中心的计算,且计算机仿真结果表明,应用该方法后融合系统的检测性能有明显的提高.     

LSFR算法在多传感器分布式检测中的优化研究

在多传感器分布式检测系统中,常规融合规则算法要求传感器误差概率已知,且系统中传感器和融合中心同时优化存在一定困难.提出最小二乘融合规则(LSFR)算法,算法不依赖噪声环境稳定性以及传感器的虚警概率与检测概率,融合中心根据各个传感器的硬决策,得到全局的硬决策,并在传感器和融合中心处理达到最优时,获得最佳全局性能.仿真结果表明:对比似然比融合决策算法与Neyman Pearson融合规则(NPFR)算法,LSFR算法全局检测概率显著提高,且在不同数量规模传感器和更多类型的分布式检测系统中具有较好兼容性.     

利用绑定技术实现分布式继承

面向对象编程语言的继承机制实现了子类和父类间is-a的关系,子类对象成为一个有效的父类对象,具有了父类对象的功能,实现了继承和扩展父类的目的。但是继承难以在分布式环境中跨网络实现,难以实现异构的分布式对象间的继承,所以在借鉴已有绑定技术的基础上,文章将绑定应用到分布式对象之间,提出了一种新的分布式继承模型:利用分布式对象间的绑定来增强和扩展分布式对象的功能,从而达到一种分布式继承的效果。     

基于要素矩阵触发的管道异常分布式检测

针对管网管道数据传输频繁的问题,为了能够对管网进行实时检测和减少站场间数据传输次数,通过研究管网站场内不同数据的类型及传输特点,建立了管网管道的运行模型,提出了基于要素矩阵触发的管道异常分布式检测方法.该分布式异常检测方法利用站场设备数据建立管道数据要素矩阵并通过提出的基于随机矩阵单环定理的异常判断准则来决定站场间数据传输的时刻,然后采用考虑管道倾角的数据衰减模型将相邻站场的压力数据进行折算并且与实际管道压力差相比较,得到管道的运行状态.该方法采用要素矩阵触发和压力数据衰减模型对数据进行传输和处理,可以减少站场间的数据传输频率以及提高检测的精度.最后通过管网站场历史数据验证了所提方法的有效性.     

A partially distributed deadlock detection algorithm

In this paper, a partially distributed deadlock detection algorithm [PDDDA] with multiple outstanding requests is presented for use in distributed database systems. This algorithm allows a process to request many resources simultaneously and uses a central controller for detecting multisite deadlocks. The detection of local deadlocks and the maintenance of local deadlock information are performed at each of the local sites. This partially distributed algorithm alleviates the problem of congestion at the central controller in a centralized algorithm and needs fewer messages and smaller storage space than a fully decentralized algorithm. A set of criteria for comparing deadlock detection algorithms are also given and then used to compare PDDDA with a fully decentralized algorithm proposed by Isloor and Marsland.Research reported herein was supported by US Army CECOM, Ft. Monmouth, New Jersey, under Contract No. DAAB07-83-K-K542. The views, opinions, and/or findings contained in this paper are those of the authors and should not be construed as an official Deportment of the Army position, policy or decision.     

Towards the construction of distributed detection programs,with an application to distributed termination

Summary Methodological design of distributed programs is necessary if one is to master the complexity of parallelism. The class of control programs, whose purpose is to observe or detect properties of an underlying program, plays an important role in distributed computing. The detection of a property generally rests upon consistent evaluations of a predicate; such a predicate can be global, i.e. involve states of several processes and channels of the observed program. Unfortunately, in a distributed system, the consistency of an evaluation cannot be trivially obtained. This is a central problem in distributed evaluations. This paper addresses the problem of distributed evaluation, used as a basic tool for solution of general distributed detection problems. A new evaluation paradigm is put forward, and a general distributed detection program is designed, introducing the iterative scheme ofguarded waves sequence. The case of distributed termination detection is then taken to illustrate the proposed methodological design. Jean-Michel Hélary is currently professor of Computer Science at the University of Rennes, France. He received a first Ph.D. degree in Numerical Analysis in 1968, then another Ph.D. Degree in Computer Science in 1988. His research interests include distributed algorithms and protocols, specially the methodological aspects. He is a member of an INRIA research group working at IRISA (Rennes) on distributed algorithms and applications. Professor Jean-Michel Hélary has published several papers on these subjects, and is co-author of a book with Michel Raynal. He serves as a PC member in an international conference. Michel Raynal is currently professor of Computer Science at the University of Rennes, France. He received the Ph.D. degree in 1981. His research interests include distributed algorithms, operating systems, protocols and parallelism. He is the head of an INRIA research group working at IRISA (Rennes) on distributed algorithms and applications. Professor Michel Raynal has organized several international conferences and has served as a PC member in many international workshops, conferences and symposia. Over the past 9 years, he has written 7 books that constitute an introduction to distributed algorithms and distributed systems (among them: Algorithms for Mutual Exclusion, the MIT Press, 1986, and Synchronization and Control of Distributed Programs, Wiley, 1990, co-authored with J.M. Hélary). He is currently involved in two european Esprit projects devoted to large scale distributed systems.This work was supported by French Research Program C³ on Parallelism and Distributed ComputingAn extended abstract has been presented to ISTCS '92 [12]     

基于移动agent的分布式入侵检测系统研究*

为了提高现有分布式入侵检测系统的效率和性能,提出了一种基于移动agent的分布式入侵检测系统模型。将移动agent技术应用于入侵检测中,并给出了其移动agent间的可靠通信方法,实现了agent的协同检测。实验结果表明,由于移动agent的应用,入侵检测系统的节点成为了可移动的部件,从而使该模型具有了更强的抗攻击性和入侵检测能力。     

An efficient delay-optimal distributed termination detection algorithm

Distributed termination detection is a fundamental problem in parallel and distributed computing and numerous schemes with different performance characteristics have been proposed. These schemes, while being efficient with regard to one performance metric, prove to be inefficient in terms of other metrics. A significant drawback shared by all previous methods is that, on most popular topologies, they take Ω(P)$\mathrm{\Omega }(P)$ time to detect and signal termination after its actual occurrence, where P   is the total number of processing elements. Detection delay is arguably the most important metric to optimize, since it is directly related to the amount of idling of computing resources and to the delay in the utilization of results of the underlying computation. In this paper, we present a novel termination detection algorithm that is simultaneously optimal or near-optimal with respect to all relevant performance measures on any topology. In particular, our algorithm has a best-case detection delay of Θ(1)$\mathrm{\Theta }(1)$ and a finite optimal worst-case detection delay on any topology equal in order terms to the time for an optimal one-to-all broadcast on that topology (which we accurately characterize for an arbitrary topology). On k-ary n  -cube tori and meshes, the worst-case delay is Θ(D)$\mathrm{\Theta }(D)$, where D   is the diameter of the target topology. Further, our algorithm has message and computational complexities of Θ(MD+P)$\mathrm{\Theta }(\mathit{MD}+P)$ in the worst case and, for most applications, Θ(M+P)$\mathrm{\Theta }(M+P)$ in the average case—the same as other message-efficient algorithms, and an optimal space complexity of Θ(P)$\mathrm{\Theta }(P)$, where M is the total number of messages used by the underlying computation. We also give a scheme using counters that greatly reduces the constant associated with the average message and computational complexities, but does not suffer from the counter-overflow problems of other schemes. Finally, unlike some previous schemes, our algorithm does not rely on first-in first-out (FIFO) ordering for message communication to work correctly.     

基于分布式Agent的入侵检测系统研究

随着网络入侵行为变得越来越普遍和复杂,传统的单一入侵检测系统已不能满足网络安全的发展需求,针对当前形势,为了提高计算机及网络系统的防御能力,提出了一种基于分布式Agent技术的入侵检测模型,并给出了一种可疑度算法和多IP地址连续报告策略,经测试和论证,系统可有效地阻止已知和未知的攻击行为,最后对系统的整体性能进行了详细描述。     

一种基于ARM-Linux的分布式管道泄漏监测系统

针对中国输油管道现场具体情况,设计一套基于嵌入式ARM-Linux和LabVIEW的分布式管道泄漏监测系统,包括远程测控终端(RTU)、监测PC以及工业局域网.详细论述了系统架构、硬件组成、软件流程等.通过实际开发与应用,证明此设计完全适用于输油管道特殊现场,不仅降低了成本与功耗,还提高了效率,为长距离石油管道运输系统...     

基于Chi-square检验的分布式网络入侵检测系统

针对网络攻击的新特点,本文提出了一种基于Chi-square检验的分布式网络入侵检测系统模型CTDIDS。设计并实现了一个基于异常检测的入侵分析引擎。通过对网络数据包的分析,运用Chi-square值比较对系统的行为进行检测。与现有的入侵检测方法相比,本文提出的方法具有更好的环境适应性和数据协同分析能力。实验证明,分布式入侵检测系统CTDIDS具有更高的准确性和扩展性。     

分布式发电系统的复合型孤岛检测方法研究

为了解决分布式发电系统中存在的孤岛检测问题,提出了一种新型复合式孤岛检测方法。该方法通过改变扰动电流波形对传统的AFD检测方法进行改进,并结合传统被动式孤岛检测方法判定孤岛现象的发生。结合IEEE.Std.2000-929/UL1741标准中的技术规范,利用Matlab/Simulink对新方法进行了仿真验证。仿真结果显示,该方法既能快速、准确地检测出孤岛现象,又把对电网电能质量的影响降到最小。     

分布式网络入侵检测代理系统的改进设计方案研究

提出了一个分布式网络入侵检测代理系统的改进设计方案,以层次式的体系结构为蓝本,结合对等式模型提出了双控中心策略,当"主控制中心"失效时,由"从控制中心"代替行使控制权,按对等式方式工作.该方案提高了系统的容错性,最大可能的避免了单点失效而引起连锁反应问题.同时给出了在移动代理整合入侵检测系统(MACIDS)框架下,基于测量服务层次协议的Agent详细设计,通信平台的3个层次、4个功能组件的划分和如何在分布式、对等式两种工作方式共享数据和资源进行通信的过程.