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Conference on Digital Avionics Systems (DASC)

作者： Hagbae Kim K.G. Shin Real-Time Computing Laboratory Department of Electrical Engineering and Computer Science University of Michigan Ann Arbor MI USA

Modeling fault behaviors such as fault occurrences and active/benign durations is an essential step to the design and evaluation of fault-tolerant controller computers. We use a beta-binomial distribution to model fault occurrences both in the presence and in the absence of environmentally-induced (thus common-cause) faults. A multinomial distribution is used to model fault active durations. The proposed model is validated by testing it against the data generated by a simulation program that mimics a common-cause fault environment. The model is then applied to the determination of an optimal time-redundancy recovery method for EMI-induced failures in an N-modular redundant controller computer, demonstrating its utility and power.< >

关键词： Fault tolerant systems Fault tolerance Nuclear magnetic resonance Electromagnetic interference real time systems Power system modeling Hardware Redundancy Temperature Electromagnetic radiation

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Replication and allocation of task modules in distributed real-time systems

Replication and allocation of task modules in distributed re...

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International Symposium on Fault-Tolerant computing (FTCS)

作者： Chao-Ju Hou K.G. Shin Computer Engineering Division Department of Elect. and Computer Engineering University of Wisconsin Madison WI USA Real-Time Computing Laboratory Department of Elect. Engineering and Comp. Science University of Michigan Ann Arbor MI USA

This paper addresses the problem of replicating and allocating periodic task modules to processing nodes (PNs) in distributed real-time systems subject to task precedence and timing constraints. The probability that all tasks can be completed before their deadlines-termed as the probability of no dynamic failure (P/sub ND/)-is used as the performance-related reliability measure. Modules which are critical in meeting task deadlines are then selected using the critical path analysis. To provide the timing correctness embedded in P/sub ND/, both original and replicated task modules are not only assigned to PNs, but also scheduled on each PN so as to meet the deadlines of all tasks. The module allocation scheme uses (1) the branch-and-bound method to implicitly enumerate all possible allocations while effectively pruning unnecessary search paths; and (2) the module scheduling scheme to schedule the modules assigned to each PN. Several numerical examples are presented to illustrate the proposed scheme.< >

关键词： real time systems Vehicle dynamics Job shop scheduling Timing Distributed computing Performance evaluation Aircraft Aerospace control Vehicles Production facilities

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FDDI-M: a scheme to double FDDI's ability of supporting synchronous traffic

FDDI-M: a scheme to double FDDI's ability of supporting sync...

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International Conference on Parallel and Distributed Systems (ICPADS)

作者： K.G. Shin Qin Zheng Real-Time Computing Laboratory Department of Electrical Engineering and Comput. Science University of Michigan Ann Arbor MI USA Mitsubishi Electric Research Laboratories Cambridge Research Center Cambridge MA USA

Synchronous messages are usually generated periodically and each of them is required to be transmitted before the generation of the next message. Due to the inherent deficiency in its Medium Access Control (MAC) protocol, an FDDI token ring can use at most one half of its ring bandwidth to transmit such synchronous traffic. This deficiency greatly reduces the FDDI's capability of supporting multimedia applications like real-time voice/video transmissions. In this paper, we show how a few simple modifications to the FDDI's MAC protocol can remove this deficiency and double a ring's ability of supporting synchronous traffic. The modified protocol, called FDDI-M, preserves all other good features of an FDDI network and can also achieve a higher throughput for asynchronous traffic than the standard FDDI and the FDDI-II, thus making it useful even for those networks without heavy synchronous traffic.

关键词： FDDI Bandwidth Synchronous generators Telecommunication traffic Token networks Media Access Protocol ANSI standards Laboratories Access protocols Throughput

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Transparent load sharing in distributed systems: decentralized design alternatives based on the Condor package

Transparent load sharing in distributed systems: decentraliz...

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Reliable Distributed Systems

作者： Chao-Ju Hou K.G. Shin T.K. Tsukada Computer Engineering Division Department of Elect. and Comp. Eng University of Wisconsin Madison WI USA Real-Time Computing Laboratory Department of Elect. Engineering and Comp. Science University of Michigan Ann Arbor MI USA

In recent years a number of load sharing (LS) mechanisms have been proposed or implemented to fully utilize system resources. We design and implement a decentralized LS mechanism based on the Condor package, and give in this paper a description of our design and implementation approaches. Two important features of the design are the use of region-change broadcasts in the information policy to provide each workstation with timely state information at the minimum communication cost, and the use of preferred list in the location policy to avoid task collisions. With these two features, we remove the central manager workstation in Condor, configure its functionalities into each participating workstation, and thus enhance the capability to tolerate single workstation failure and the reliability of Condor. We also discuss the experiments we conduct on the LS mechanism and the observations we obtained from empirical data.< >

关键词： Workstations Packaging Kernel software packages Chaotic communication Design engineering Broadcasting Costs Availability Delay

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Meeting the strict real-time requirements of distributed continuous multimedia applications

Meeting the strict real-time requirements of distributed con...

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IEEE International Conference on Systems, Man and Cybernetics

作者： W.A. Halang P.A. Laplante A.D. Stoyenko Faculty of Electrical Engineering FernUniversität Hagen Hagen Germany Department of Mathematics and Computer Science Fairleigh Dickinson University Madison NJ USA Real Time Computing Laboratory Department of Computer and Information Sciences New Jersey Institute of Technology Newark NJ USA

In this paper we discuss synchronization techniques-and specifically their implementation at the hardware, operating system and high-level language levels-that can be used to achieve deadline satisfaction. In particular, it is shown that by endowing process control computers with fully parallel input and output mechanisms making use of exact time specifications, synchronization and deadline satisfaction can be achieved at the same time without any jitter. Continuous multimedia applications require accurate synchronization of the clocks in different processors. The available solutions have considerable accuracy or applicability. Local clock synchronization by radio transmitted time information turns out to be the only general purpose and high accuracy technique that is applicable with reasonable effort.< >

关键词： Application software Synchronization Multimedia computing Virtual reality Colored noise Hardware Operating systems TV Clocks Multimedia systems

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Flexible automation of hardware design tasks using software process technology

Flexible automation of hardware design tasks using software ...

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Symposium on Assessment of Quality software Development Tools

作者： B.J. Kramer B. Dinler W.A. Halang A.D. Stoyenko Faculty of Electrical Engineering Fern Universität Hagen Hagen Germany GMD Institut SET Sankt Augustin Germany Faculty of Electrical Engineering Fern Universitat Hagen Hagen Germany Computer & Inforamtion Science New Jersey Institute of Technology Real-Time Computing Laboratory Newark NJ USA

This paper describes a hybrid approach towards design management. It was applied in a case study linking automated software development and behavioral synthesis. The process-centered software development environment MARVEL is combined with the ALLIANCE design tool box to provide a flexible hardware design management environment. It automatically activates tools according to the design flow, checks access rights of designers, and maintains consistency of design data. Some lessons learned from the experiment are reported.< >

关键词： Design automation Hardware software design Programming Process design Environmental management Application software Laboratories Information science software development management

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ANALYTIC MODELS OF ADAPTIVE LOAD SHARING SCHEMES IN DISTRIBUTED real-time SYSTEMS

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IEEE TRANSACTIONS ON PARALLEL AND DISTRIBUTED SYSTEMS 1993年第7期4卷 740-761页

作者： SHIN, KG HOU, CJ Real-Time Computing Laboratory Department of Electrical Engineering and Computer Science University of Michigan Ann Arbor MI USA

In a distributed real-time system, nonuniform task arrivals may temporarily overload some nodes while leaving some other nodes idle. As a result, some of the tasks on an overloaded node may miss their deadlines even if the overall system has the capacity to meet the deadlines of all tasks. In a companion paper [1], we proposed, without any modeling analysis, a decentralized, dynamic load sharing (LS) scheme as a solution to this problem. In this paper, we develop analytic queueing models to comparatively evaluate the proposed LS scheme as well as three other schemes: no LS, LS with random selection of a receiver node, and LS with perfect information. The evolution of a node's load state is modeled as a continuous-time semi-Markov process, where cumulative execution time (CET), rather than the commonly-used queue length (QL), is employed to describe the workload of a node. Not only fundamental differences among the different LS schemes are addressed in the analytic models, but also implementation overheads are taken into account Several metrics relevant to real-time performance are derived from these models: in particular, we evaluate the probability of a task missing its deadline, called the probability of dynamic failure. The proposed scheme is compared against other LS schemes using these performance metrics. The validity of analytic models is checked with simulations. Both analytic and simulation results indicate that by using judicious exchange/use of state information and Bayesian decision mechanism, the proposed scheme makes a significant improvement over other existing LS schemes in minimizing the probability of dynamic failure.

关键词： BAYESIAN ANALYSIS CONTINUOUS-time MARKOV CHAINS DEADLINES DISTRIBUTED real-time SYSTEMS LOAD SHARING LOCATION AND TRANSFER POLICIES PERFORMANCE EVALUATION RANDOM PROBING AND SELECTION

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A SIMPLE DISTRIBUTED LOOP-FREE ROUTING STRATEGY FOR COMPUTER-COMMUNICATION NETWORKS

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IEEE TRANSACTIONS ON PARALLEL AND DISTRIBUTED SYSTEMS 1993年第12期4卷 1308-1319页

作者： SHIN, KG CHOU, CC Real-Time Computing Laboratory Computer Science and Engineering Division Department of Electrical Engineering and Computer Science University of Michigan Ann Arbor MI USA

The loops resulting from either component failures or Load changes in a computer communication network degrade the performance and the adaptability of conventional distributed adaptive routing strategies, such as ARPANET's previous routing strategy (APRS). In this paper, we develop a distributed loop-free routing strategy by adding only one additional piece of information-the total number of minimum-delay paths-to the commonly used routing messages and tables. Most conventional approaches to the looping problem suffer high overheads in time and space because each message must either include the first several nodes of its path or trace the entire path to detect a loop. By contrast, the proposed routing strategy requires only easily obtainable information, yet removes loops completely. It is far more efficient in both time and space than its conventional counterparts, especiallyTable Ifor sparse computer networks. The correctness of the proposed strategy is proved, and several illustrative e?xamples are given. The performance of this strategy is shown to be always better than, or at least as good as, that of APRS and any multiorder routing strategies, where the order of a routing strategy is determined by the amount of routing information carried in each routing message.

关键词： ARPANET COMPUTER COMMUNICATION NETWORKS DISTRIBUTED ADAPTIVE ROUTING LOOP-FREE OR FAULT-TOLERANT ROUTING NETWORK DELAY TABLES STRATEGY ROUTING MESSAGES

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MIXED time-CONSTRAINED AND NON-time-CONSTRAINED COMMUNICATIONS IN LOCAL-AREA NETWORKS

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IEEE TRANSACTIONS ON COMMUNICATIONS 1993年第11期41卷 1668-1676页

作者： SHIN, KG ZHENG, Q Department of Electrical Engineering and Computer Science Real-Time Computing Laboratory University of Michigan Ann Arbor MI USA Mitsubishi Electric Research Laboratories Inc. Cambridge MA USA

It is well known that some time-token medium access protocols for local area networks (LANs) like the IEEE 802.4 token bus and the FDDI token ring can guarantee the medium access delay for time-constrained packets. However, a problem which has been largely overlooked is how these protocols can be made to provide a maximum throughput for nontime-constrained packets while guaranteeing the delay bound of time-constrained packets. We first show how the parameters of the IEEE 802.4 token bus and the FDDI token ring can be set to solve the above problem. Then, we design a new timer mechanism for the timed-token protocols which provides the highest guaranteed throughput of nontime-constrained packets among a set of medium access protocols called the token passing protocol, to which most of the existing non-contention LAN protocols belong. We present numerical examples to compare different protocols, all of which have shown the superiority of the proposed protocol to the others.

关键词： MIXING time Packet token bus Local Area Networks Token ring fiber distributed data interface (FDDI) Media Access Protocol

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Incorporation of optimal timeouts into distributed real-time load sharing 26

Incorporation of optimal timeouts into distributed real-time...

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26th Hawaii International Conference on System Sciences, HICSS 1993

作者： Hou, C.-J. Shin, K.G. Real-Time Computing Laboratory Department of Electrical Engineering and Computer Science University of Michigan Ann ArborMI48109-2122 United States

ISBN: (纸本)0818632305

This paper addresses the problem of designing and incorporating a timeout mechanism into load sharing (LS) with state-region change broadcasts in the presence of node failures in a distributed real-time system. Failure of a node is diagnosed by the other nodes through communication timeouts, and the timeout period used to diagnose whether a node is faulty or not depends on the dynamic changes in system load, the task attributes at the node, and the state the node was initially in. We formulate the problem of determining the 'best' timeout period Tiout for node i as a hypothesis testing problem, and maximize the probability of detecting node failures subject to a prespecified probability of falsely diagnosing a healthy node as faulty. The parameters needed for the calculation of Tiout are estimated on-line by node i using the Bayesian technique and are piggybacked in its region-change broadcasts. The broadcast information is then used to determine Tiout. If node n has not heard from node t for T Tiout since its receipt of node i's broadcast, it will consider node i failed. On the other hand, each node n also determines its own timeout period Tnout, and broadcasts its state not only at the time of state-region changes but also when it has remained within a broadcast-threshold interval throughout Tnout. Our simulation results show that the LS algorithm which combines the on-line parameter estimation, the timeout mechanism, and a few extra, timely broadcasts can significantly reduce the probability of missing task deadlines. © 1993 IEEE.

关键词： Probability

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