A decomposition technique for the overall reliability evaluation of large computer communication networks

A funtamental consideration in the design of a computer network is the determination of its overall reliability. For large computer networks the exact evaluation of overall reliability is prohibitive because of the complexity of the computations involved. In this paper an approximate technique for the overall reliability determination is proposed which is based on the m-hierarchical clustering of a network. By this approach a close lower bound for the exact overall reliability can always be obtained with important savings in computation time and available memory.     

An availability evaluation for computer communication networks

Among the various availability criteria for computer communication networks, based on strictly topological considerations or taking into account also the traffic characteristics, we propose, as a network performance measure, the probability that an assigned fraction of the stability throughput can be carried out with average packet and message time delays not greater than specified values.At the aim, an algorithm for the availability analysis has been developed; given the topological and physical characteristics of the network, the external traffic statistics at the network node pairs and the routing procedure, the network availability and the average loss of throughput due to single failures of lines or switching nodes are evaluated with regard, as an example, to a simple five node network.     

Overall reliability determination of computer networks with hierarchical routing strategies

This paper determines the overall reliability of a computer network in which hierarchical routing strategies are used for the communication between its nodes.An exact method is presented which is followed by three fast computer techniques corresponding to three different routing policies. The first two give the exact value for the overall reliability while the third provides a lower bound which is very close to the exact reliability value. The main advantages of these techniques are the important savings in computation time and available memory. The developed algoriths are very useful in the overall reliability evaluation of large networks or many interconnected subnetworks.     

Empirical prediction of overall reliability in computer communication networks

Incorporation of an overall reliability parameter in the design of reliable computer communication networks makes the computation prohibitive. A composite reliability index based on the network topological parameters has been presented [1], which is very simple to evaluate and gives computation while designing maximally reliable computer networks as compared to the techniques based on several reliability measures. In this paper, we use the tabulated results of Soi and Aggarwal [1] and develop empirical formulae which can be used for quick estimation of overall reliability of a computer network for a specified value of the link reliability.     

Estimation of reliability for communication/computer networkssimulation/analytic approach

A general simulation/analytic approach for jointly assessing the reliability and performance of a communication/computer network is proposed. The advantages of this approach are the following: (a) it allows consideration of a variety of performance measures, (b) it allows consideration of a general structure of network components failure distribution, (c) it reduces complexity of the model and related calculations, (d) it is relatively simple to implement, and (e) it can derive sensitivity information about network performance with respect to various parameters-the first step for an effective network optimization algorithm. The method is illustrated in a number of examples using network connectivity and weighted network bandwidth as a measure of performance     

An introduction to large deviations for communication networks

This paper is an introduction to some large deviations techniques that have been used for analyzing models of communication networks. Starting from the beginning (sequences of i.i.d. random variables), it progresses to some Markov processes in discrete or continuous time. It illustrates the meaning of most theorems by applying them to a common example. Then the AMS model of buffering in ATM is analyzed in a variety of ways. Finally, a few other common models are discussed     

Comparison of a simulation and an exact method for reliability evaluation of large networks using a personal computer

An analysis of the relative merits and demerits of a simulation and an exact method for system reliability evaluation is presented. The comparison is performed using computer programs developed on a personal computer. The networks used in the analysis are randomly generated. Although computer implementations of some system reliability evaluation methods are available in the reliability literature, the programs are not portable. Most of the programs were developed either on a mainframe or a mini computer in different software environments. Due to the recent developments in computer technology, extremely fast personal computers are available. The emphasis of this paper is on the use of a standard personal computer, such as the IBM-PC or a compatible, in order to develop and compare computerized algorithms.     

A computer approach for reliability evaluation of telecommunicationnetworks with heterogeneous link-capacities

The authors present a computer approach to obtaining a survivability index called capacity related reliability (CRR) in large telecommunication networks where links have different capacities. The method is a two-step approach. The first step deals with composite path enumeration (CPE). A k-composite path is defined as the union of the set of edges in any k simple paths and relates link capacity and network connectivity. The CPE approach is an improvement over the algorithms proposed by the authors earlier (1991). In step two, k-composite paths information is manipulated to generate the CRR. The authors use CAREL (computer aided reliability evaluator) to solve this step. The technique is automated using C on the Encore Multimax System. The results on CRR for three networks with various values of minimum message capacity are presented. An exhaustive technique is used to verify these results. An informal proof of the CPE approach is also included     

Multiwavelength lightwave networks for computer communication

The different approaches being considered to build high-capacity lightwave networks are described. Two kinds of lightwave network architectures are examined: broadcast-and-select networks and wavelength-routing networks. A comparison of the two shows that broadcast-and-select networks may be more suitable for local area networks (LANs) and metropolitan area networks (MANs), while wavelength-routing networks are suitable for wide area networks (WANs). The overall network may then be a combination of broadcast subnets interconnected by a point-to-point wavelength-routing network     

An architecture design approach for large satellite networks

Designing a world-wide satellite network that consists of hundreds of user sites and thousands of circuit connections is a complex problem, which involves selecting a set of candidate satellites and satellite beams/frequency bands from among numerous existing and planned satellites, evaluation of circuit connectivity, earth-station compatibility and sizing, and estimating transponder loading. The design process may also require assessment of the impact of a different set of satellites and modified user traffic requirements on the space segment, the earth-station types and quantity, and the total system cost. Although a conventional design approach based on link-by-link and site-by-site analysis provides accurate results, it is time-consuming and impractical for developing high-level network architectures in a time-constrained environment. A design technique is proposed which employs a set of rules for satellite network design, in combination with extensive databases of satellite parameters, earth-station parameters and user traffic requirements, to synthesize a network architecture. The technique is particularly useful for performing high-level trade-offs among alternative architectures in terms of space segment requirements, the number and type of earth-stations and overall system cost. Once the desired architecture has been selected, a detailed design may be developed using conventional methods.     

提高通信网络可靠性的方法探析

从产品的可靠性定义出发,通过对通信网络可靠性的分析得出了影响通信网络可靠性的因素。从提高节点／设备的可靠性、优化拓扑结构、使用网络保护与恢复技术、使用差错控制技术等几个方面详细介绍了提高通信网络可靠性的方法和需要注意的问题,并简要说明了其它的方法。最后,指出这些方法已经运用于工程实践并被证明切实有效。     

Empirical relationship between communication costs and the channel bit rate for large computer networks

The primary trade-off in a large computer-communication network (CCN) is the balance between computation processing capability and communication capability. Essentially, a CCN model should utilize operational optimization (rather than mathematical optimization) allowing the user (mostly a non-programme network expert) to call upon his experience and insight in dealing with real-life networks to decide upon proper direction for modifications. We propose, in this paper, a unified approach which will hopefully allow an on-line user to make real-time modifications to CCNs to obtain operationally optimal system trade-offs in such areas as network overall reliability, communication response, computation response, and optimum channel capacities etc.     

Testing communication and computer networks: an overview

Many activities in today's organizations are becoming ever more dependent on communications and computer networks, and network managers are faced with the enormous challenge of increasing the availability and efficiency of their infrastructures, which grow both in size and complexity. This makes it crucial to plan network operation systematically, to define and implement appropriate procedures for regular monitoring and performance assessment, and to set up proper tools for maintenance and troubleshooting purposes. Furthermore, proactive network testing must be pursued; it is vital to gather some ideas of normal network operation documented in order to have a comparison term when problems occur. The article has dealt with the measurement instruments and procedures currently adopted for network testing and advances in the field for the I&M research community.     

Reliability polynomials of computer communication networks

The expression for the overall reliability of a computer communication network (CCN) when all edges have equal probability of being up is called the reliability polynomial of the CCN. For a complicated network, the overall reliability of the CCN can be approximated by the truncated polynomial. A characterization of the reliability polynomial and its approximation are give in this paper.     

On computer communication network reliability under programexecution constraints

The authors propose a technique to compute software system reliability (SSR). The method, called FARE (fast algorithm for reliability evaluation), does not require a priori knowledge of multiterminal connections (MCs) for computing the reliability expression. An effort is made to sole the problem of N-version programming by using the FARE approach. Owing to its short execution time and low memory requirement, FARE can be used to calculate the SSR of fairly large distributed systems     

An analytical framework for reliability evaluation of d-dimensional IEEE 802.11 broadcast wireless networks

Wireless Networks - In this paper, we validate that the deterministic distance-based analytical model can be used to estimate the reliability of one-dimensional (1-D) 802.11 broadcast wireless...     

通信网可靠性综合评估

影响通信网的可靠性因素很多。在考虑多个测度指标的情况下,通信网可靠性评估是多指标的综合评价,提出了三种综合评估方法。其中基于神经网络的综合评判较好地解决了综合评价指标中各指标的权数确定又尽可能地排除了人为因素的影响这一难题。     

Modification of cutsets for reliability evaluation of communication systems

A general and simple technique for the evaluation of symbolic reliability expression in the case of practical systems such as a communication system having fixed channel capacities of its various communicating links, a computer communication network allowing a fixed amount of data exchange amongst different terminals of various computer centres and a power distribution system having limited power ratings of its various power lines, is presented. A system is considered reliable only if it successfully transmits at least the required system capacity from the transmitter to the receiver station. In this method, the various branch sets are obtained which completely disrupt the communication path, i.e. ensure system failure. It is observed that these branch sets are not necessarily the cutsets in the usual graph theoretic sense. The unreliability expression is then determined by adopting an existing method for making various terms disjoint. Two typical examples are solved by this method. It is observed that the method is computationally fast and efficient.     

改进计算机网络可靠性的方法探析

计算机网络的可靠性设计与建设问题的解决方法是当前相关领域的研究热点问题,其对于保证计算机网络安全稳定的运行有着重要的意义。