令牌多环网性能—可靠性综合评价

网络的性能与可靠性已分别得到广泛的研究,然而,怎样分析具有容错机制的环网的性能仍属有待开拓的研究领域,本文提出了一种分析具有自修复机制的多环网络系统的方法,并给出了报文传输时间分布的拉氏变换式,平均等待时间及平均队列长度公式,分析结果可用于评估故障与修复过程对实时令牌环网的实时响应特性的影响,对基于LAN的分布式实时系统设计具有指导意义。     

A combined queueing network and stochastic Petri-net approach for evaluating the performability of fault-tolerant computer systems

In this paper the performability analysis of fault-tolerant computer systems using a hierarchical decomposition technique is presented. A special class of queueing network (QN) models, the so-called BCMP [4], and generalized stochastic Petri nets (GSPN) [1] which are often used to separately model performance and reliability respectively, have been combined in order to preserve the best modelling features of both.

A conceptual model is decomposed into GSPN and BCMP submodels, which are solved in isolation. Then, the remaining GSPN portion of the model is aggregated with flow-equivalents of BCMP models, in order to compute performability measures. The substitutes of BCMP models are presented by means of simple GSPN constructs, thereby preserving the 1st and 2nd moments of the throughput. A simple example of a data communication system where failed transmissions are corrected, is presented.     

一类评价计算机控制系统全面品质的综合准则及其应用

提出一类用于分析和评价计算机控制系统性能、可靠性和经济性全面品质的综合准则，讨论了能运行性的概念。本文所指的经济性为从系统制造至运行全过程中的整体效益。针对水轮机调阳系统进行了具体研究，对不同的系统结构进行了比较研究。提出的方法对优选和设计具有优良综合品质的计算机控制系统是有效的。     

Network dimensioning at the call level for the always‐on network

It is becoming common for the network to provide always‐on access services, where subscribers are guaranteed that their call requests will never be blocked. This paper studies the call‐level link dimensioning for the always‐on network with single‐class traffic. The call‐level QoS requirement is expressed in terms of the probability of a poor‐quality call, which is the probability that a call experiences packet‐level QoS violation at any time during its duration, as opposed to the probability of blocking in the network with call admission control (CAC). The system is modelled as the M/M/infinite system with finite population and an analytic expression for the probability of a poor‐quality call is derived based on performability analysis. The effects of the call‐level traffic characteristics on the required link resources are studied. It is also shown that the call‐level link dimensioning for the always‐on network needs more link resources than the network with CAC, and the call‐level link dimensioning based on the analytic expression can be used to conservatively dimension the always‐on network with arbitrarily distributed call holding time and inter‐call time. The paper also studies the problem of estimating the call‐level traffic characteristics when the knowledge of call boundaries is not available. Copyright © 2004 John Wiley & Sons, Ltd.     

Influences of temperature and salinity on holistic network performability of multi-AUV cooperative systems

This study proposes holistic network performability as a reliability index of multiple autonomous underwater vehicle (AUV) (multi-AUV) cooperative systems and deduces the reliability of communication links. Temperature and salinity vary in different areas of the sea. The influence mechanism of temperature and salinity on holistic network performability is discussed. An example is provided to show the influences of temperature and salinity on holistic network performability. Corresponding trends of holistic network performability with the influences of temperature and salinity can be obtained. The trends show that the holistic network performability of multi-AUV cooperative systems exhibit ladder-like increases with temperature and salinity. In each ladder, the value of holistic network performability changes rapidly at high salinity or low temperature. The study on the change of the reliability of multi-AUV cooperative systems under different temperatures and salinities provides a theoretical basis for the reliability research of multi-AUV cooperative systems and provides reference for future practical application of multi-AUV cooperative systems and other network systems.     

地域通信网可靠性测度指标研究进展

在研究地域通信网可靠性定义及其影响因素基础上，系统分析了国内外对地域通信网可靠性测度指标研究的现状与进展和存在的问题，并研究了建立可靠性测度指标体系应解决的关键问题．     

Sensitivity analysis of performability

An analytical expression is provided to evaluate the sensitivity (i.e. the derivative with respect to a system parameter) of the cumulative reward distribution for systems modeled by homogeneous Markov reward processes. Both transition rates and reward rates are assumed to be function of the system parameter. An upper bound is also provided for the error introduced by the numerical evaluation of the sensitivity.     

Computer-aided reliability analysis of fault-tolerant systems

We present an overview of the major problems inherent in reliability modelling of fault-tolerant systems. The problems faced while modelling such systems include the need to consider a very large state space, non-exponential distributions, error analysis, the need to perform a combined evaluation of performance and reliability, and the need to include the details of fault/error handling behaviour. Some of the proposed solutions are discussed and current tools (harp, save, deep andsharpe) to facilitate evaluation of such systems are described. References are provided to many of the important techniques utilized in reliability, availability, and performance modelling of such systems. This research was supported in part by the Air Force Office of Scientific Research under grant AFOSR-84-0132, by the Army Research Office under contract DAAG29-84-0045 and by the National Aeronautics and Space Administration under grant NAG1-70.     

基于网络状态之间关系的网络的可靠性分析

本文在讨论了电信网不同状态通过量之间的一般性关系后，得到了一种不需枚举所有网络状态来计算网络可行性（ｐｅｒｆｏｒｍａｂｉｌｉｔｙ）精确值的方法。以此为基础，对不同数目失效链路所有网络状态中最大通过量和最小通过量的状态之间的关系进行了研究，得到了快速计算电信网可行性精确值，近似值及其上下界的方法。同时得到了一种快速估计网络链路重要性的方法。     

Performability: a retrospective and some pointers to the future

As computing and communication systems become physically and logically more complex, their evaluation calls for continued innovation with regard to measure definition, model construction/solution, and tool development. In particular, the performance of such systems is often degradable, i.e., internal or external faults can reduce the quality of a delivered service even though that service, according to its specification, remains proper (failure-free). The need to accommodate this property, using model-based evaluation methods, was the raison d'être for the concept of performability. To set the stage for additional progress in its development, we present a retrospective of associated theory, techniques, and applications resulting from work in this area over the past decade and a half. Based on what has been learned, some pointers are made to future directions which might further enhance the effectiveness of these methods and broaden their scope of applicability.