Deng-Jyi Chen

Reliability analysis of distributed systems based on a fast reliability algorithm

The reliability of a distributed processing system (DPS) can be expressed by the analysis of distributed program reliability (DPR) and distributed system reliability (DSR). One of the good approaches to formulate these reliability performance indexes is to generate all disjoint file spanning trees (FSTs) in the DPS graph such that the DPR and DSR can be expressed by the probability that at least one of these FSTs is working. In the paper, a unified algorithm to efficiently generate disjoint FSTs by cutting different links is presented, and the DPR and DSR are computed based on a simple and consistent union operation on the probability space of the FSTs. The DPS reliability related problems are also discussed. For speeding up the reliability evaluation, nodes merged, series, and parallel reduction concepts are incorporated in the algorithm. Based on the comparison of number of subgraphs (or FSTs) generated by the proposed algorithm and by existing evaluation algorithms, it is concluded that the proposed algorithm is much more economic in terms of time and space than the existing algorithms. >

A heuristic approach to generating file spanning trees for reliability analysis of distributed computing systems

Abstract The reliability of Distributed Computing Systems (DCS) in terms of Distributed Program Reliability (DPR) and Distributed System Reliability (DSR) has been studied intensively. Current reliability algorithms available for the analysis of DPR and DSR include MFST, FARE, FST, and FST-SPR. This paper presents a reliability algorithm, called HRFST, that eliminates the need to search a spanning tree during each subgraph generation. The HRFST algorithm reduces both the number of subgraphs (or trees) generated and the actual execution time required for analysis of DPR and DSR. Examination of several sample cases shows that the HRFST algorithm is more efficient than the FST-SPR algorithm.

Efficient algorithms for reliability analysis of distributed computing systems

Abstract A distributed computing system is modeled as a collection of resources (e.g. processing elements, data files and programs) interconnected via an arbitrary communication network and controlled by a distributed operating system. The distributed program reliability in a distributed computing system is the probability of successful execution of a program running on multiple processing elements and needs to retrieve data files from other processing elements. This reliability varies according to (1) the topology of the distributed computing system, (2) the reliability of the communication edges, (3) the data files and programs distribution among processing elements and (4) the data files required to execute a program. In addition, computing the reliability of distributed computing systems is #P -complete even when the distributed computing system is restricted to a series-parallel, a 2-tree, a tree, or a star structure. This paper presents efficient algorithms for computing the reliability of a distributed program running on other restricted classes of networks.

The distributed program reliability analysis on ring-type topologies

Abstract Distributed computing system (DCS) has become very popular for its high fault-tolerance, potential for parallel processing, and better reliability performance. One of the important issues in the design of the DCS is the reliability performance. Distributed program reliability (DPR) is addressed to obtain this reliability measure. In this paper, we propose a polynomial-time algorithm for computing the DPR of ring topology and show that solving the DPR problem on a ring of trees topology is NP-hard. Scope and purpose The widespread use of distributed computing system is due to the price–performance revolution in microelectronics, the development of cost-effective and efficient communication subsets, the development of resource sharing software, and the increased user demands for communication, economical sharing of resources, and productivity. This article is concerned with the analysis of distributed program reliability on a ring-distributed computing system. The distributed program reliability is a useful measure for reliability evaluation of distributed computing system. The distributed program reliability analyses also give a good index for designing a high-reliability-performance-distributed computing system.

The distributed program reliability analysis on star topologies

Abstract A distributed computing system consists of processing elements, communication links, memory units, data files, and programs. These resources are interconnected via a communication network and controlled by a distributed operating system. The distributed program reliability in a distributed computing system is the probability that a program which runs on multiple processing elements and needs to retrieve data files from other processing elements will be executed successfully. This reliability varies according to (1) the topology of the distributed computing system, (2) the reliability of the communication edges, (3) the data files and programs distribution among processing elements, and (4) the data files required to execute a program. In this paper, we show that computing the distributed program reliability on the star distributed computing systems is NP-hard. We also develop an efficiently solvable case to compute distributed program reliability when some additional file distribution is restricted on the star topology. Scope and purpose Recent advances in VLSI circuitry have a tremendous impact on the price-performance revolution in microelectronics. This development has led to an increased use of workstations connected in the form of a powerful distributed computing system. Potential benefits offered by such distributed computing systems include better cost performance, enhanced fault tolerance, increased system throughput, and efficient sharing of resources. Distributed program reliability is an important measure that should be examined for designing a high fault-tolerance distributed computing system. This reliability varies according to (1) the topology of the distributed computing system, (2) the reliability of the communication edges, (3) the data files and programs distribution among processing elements, and (4) the data files required to execute a program. This article is concerned with the analysis of distributed program reliability on star distributed computing systems.

Reliability optimization of distributed computing systems subject to capacity constraints

In this paper, we propose a simple, easily programmed exact method for obtaining the optimal design of a distributed computing system in terms of maximizing reliability subject to memory capacity constraints. We assume that a given amount of resources are available for linking the distributed computing system. The method is based on the partial order relation. To speed up the procedure, some rules are proposed to indicate conditions under which certain vectors in the numerical ordering that do not satisfy the capacity constraints can be skipped over. Simulation results show that the proposed algorithm requires less time and space than exhaustive method.

The Reliability Analysis of Distributed Computing Systems with Imperfect Nodes

The reliability of a distributed computing system depends on the reliability of its communication links and nodes and on the distribution of its resources, such as programs and data files. Many algorithms have been proposed for computing the reliability of distributed computing systems, but they have been applied mostly to distributed computing systems with perfect nodes. However, in real problems, nodes as well as links may fail. This paper proposes two new algorithms for computing the reliability of a distributed computing system with imperfect nodes. Algorithm I is based on a symbolic approach that includes two passes of computation. Algorithm II employs a general factoring technique on both nodes and edges. Comparisons with existing methods show the usefulness of the proposed algorithms for computing the reliability of large distributed computing systems.

A probability model for reconstructing secret sharing under the Internet environment

Internet technologies have ushered in a new era for computer-related communications.Use of the Internet for commercial applications and resource sharing has accelerated in recent years as well. Owing to such developments, Internet security has become a critical issue for both academic and commercial sectors. Several studies have focused on areas involving network security such as authentication, privacy, and integrity. In some applications, an important message can be divided into pieces and allocated at several different sites over the Internet for security access concern. For example, an important map that can be used to access a military base, a vital key that can be used to give a military order or command. To access such an important message, one must reconstruct the divided pieces from different sites under the given Internet environment. In this paper, we present a novel probability model for reconstructing secret sharing under the Internet. Also, how to assign the divided shares into different sites over the Internet is studied. Also proposed herein are algorithms to perform shares assignment and to evaluate the probability of reconstructing the divided pieces into the original secret. Illustrative examples and simulation results demonstrate the feasibility of the proposed approach.

A heuristic algorithm for the reliability-oriented file assignment in a distributed computing system

Abstract Distributed Computing Systems (DCS) have become a major trend in todays computer system design because of their high speed and high reliability. Reliability is an important performance parameter in DCS design. Usually, designers add redundant copies of software and/or hardware to increase the systems reliability. Thus, the distribution of data files can affect the program reliability and system reliability. The reliability-oriented file assignment problem is to find a file distribution such that the program reliability or system reliability is maximized. In this paper, we develop a heuristic algorithm for the reliability-oriented file assignment problem (HROFA), which uses a careful reduction method to reduce the problem space. Our numerical results indicate that the HROFA algorithm obtains the exact solution in most cases and the computation time is significantly shorter than that needed for an exact method. When HROFA fails to give an exact solution, the derivation from the exact solution is very small.

Parallel routing algorithms for incomplete hypercube interconnection networks

A severe restriction on a complete hypercube topology is that the number of processors must be a power of 2. Such a restriction limits its applicability. An incomplete hypercube may provide more flexibility in system sizes. There are three classes of variant incomplete hypercube interconnection networks: I/sup r//sub m/, I/sup r//sub M/ and I/sup r//sub A/. The authors focus on the parallel routing algorithms for these three classes of incomplete hypercubes. Parallel paths between any given two nodes mean that these paths have the same source and destination nodes but with different intermediate nodes. Parallel communication can speed up the data transfer operation and increase the system fault-tolerance and the communication reliability between two nodes.<<ETX>>