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Evaluation of Communication Latency in VMEbus-Based real-time Control Systems

IFAC Proceedings Volumes 1995年第5期28卷 421-425页

作者： Jaehyun Park Kang G. Shin Real-Time Computing Laboratory Department of Electrical Engineering and Computer Science The University of Michigan Ann Arbor MI 48109-2122 U.S.A

Although the VMEbus has been widely used for real-time control systems, its real-time performance has not been evaluated thoroughly. This paper evaluates the latency of interprocessor communication in a VMEbus-based real-time control system. To minimize communication latency, mixed priority/round-robin (MPR) bus arbitration is proposed and its performance is evaluated along with standard PRI and RRS arbitration. The latency is evaluated via computer simulations and experimental measurements using a high-resolution timing-measuring instrument that can be directly plugged into the VMEbus.

关键词： real-time systems performance evaluation multiprocessor systems

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A constraint function classification for complex systems development

A constraint function classification for complex systems dev...

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IEEE International Conference on Engineering of Complex computer Systems

作者： M.S. Harelick T.J. Marlowe A.D. Stoyenko P. Sinha Real-Time Computing Laboratory Department of Computer and Information Science New Jersey Institute of Technology Newark NJ USA Department of Mathematics and Computer Science Seton Hall University South Orange NJ USA

A complex application consists of a set of software modules, executed on a distributed system, guided by requirements imposed by the designer and the system. The real project at NJIT has been investigating the resource allocation problem for such a system. We give a classification of and syntax for constraints, provide a rule-based approach for constraint management, and discuss issues in generating implied constraints and consistency checking.

关键词： Resource management Subspace constraints real time systems Distributed computing Application software Costs Laboratories information science Communication system software Hardware

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Probing and fault injection of protocol implementations

Probing and fault injection of protocol implementations

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International Conference on Distributed computing Systems

作者： S. Dawson F. Jahanian Real-Time Computing Laboratory Electrical Engineering and Computer Science Department University of Michigan Ann Arbor MI USA Electrical Engineering and Computer Science Department University of Michigan Ann Arbor MI USA

Ensuring that a distributed system with strict dependability constraints meets its prescribed specification is a growing challenge that confronts software developers and system engineers. This paper presents a technique for probing and fault injection of fault-tolerant distributed protocols. The proposed technique, called script-driven probing and fault injection, can be used for studying the behavior of distributed systems and for detecting design and implementation errors of fault-tolerant protocols. The focus of this work is on fault injection techniques that can be used to demonstrate three aspects of a target protocol: i) detection of design or implementation errors, ii) identification of violations of protocol specifications, and iii) insight into design decisions made by the implementers. The emphasis of our approach is on experimental techniques intended to identify specific "problems" in a protocol or its implementation rather than the evaluation of system dependability through statistical metrics such as fault coverage. To demonstrate the capabilities of this technique, the paper describes a probing and fault injection tool, called the PFI tool (Probe/Fault Injection Tool), and a summary of several extensive experiments that studied the behavior of two protocols: the transmission control protocol (TCP) and a group membership protocol (GMP).

关键词： Protocols Fault detection Fault diagnosis Software systems Systems engineering and theory Fault tolerance Fault tolerant systems Probes

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On slot allocation for time-constrained messages in DQDB networks

On slot allocation for time-constrained messages in DQDB net...

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IEEE Annual Joint Conference: INFOCOM, IEEE computer and Communications Societies

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

The paper addresses the issue of guaranteeing the timely delivery of isochronous messages with hard deadlines in a distributed queue dual bus (DQDB) network. The authors propose a slot allocation scheme which can allocate bandwidth for a set of isochronous message streams and provide deterministic deadline guarantees. The allocation scheme is guaranteed to find a feasible slot allocation (in the sense that all messages can be transmitted in a timely manner) as long as the total message density is less than or equal to a certain threshold, where the total message density is defined as the summation (over all message streams) of the ratio of maximum message size to message deadline. The implementation of this scheme is simple and does not require any change of the current DQDB standard.

关键词： Intelligent networks Traffic control Bandwidth Videoconference Access protocols Media Access Protocol Communication system traffic control Chaotic communication Laboratories Communication standards

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On non-existence of optimal local synchronous bandwidth allocation schemes for the timed-token MAC protocol

On non-existence of optimal local synchronous bandwidth allo...

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International Phoenix Conference on computers and Communications (IPCCC)

作者： Ching-Chih Han K.G. Shin Chao-Ju Hou Department of Elec. Engineering and Comput. Science Real-Time Computing Laboratory University슠of슠Michigan Ann Arbor MI USA Computer Engineering Division Department of Elec. and Comput. Engineering University of Wisconsin Madison WI USA

Numerous methods have been proposed to integrate real-time and non-real-time services of the timed-token medium access control (MAC) protocol. One of the key issues in tailoring the timed-token protocol for real-time applications is the synchronous bandwidth allocation (SBA) problem whose objective is to meet both the protocol and deadline constraints. Several non-optimal local SBA schemes and two optimal global schemes have been proposed. Local SBA schemes use only information available locally to each node, and are thus preferred to global schemes because of their lower network-management overhead. However, we formally prove, using the technique of adversary argument, that there does not exist any optimal local SBA scheme. During the preparation for this proof, we also derive a timing property that generalizes the previous findings about the cycle-time properties of the timed-token protocol.< >

关键词： Channel allocation Access protocols Media Access Protocol Timing Bandwidth Laboratories real time systems Multimedia systems Production facilities Communication industry

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Preface

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Lecture Notes in computer science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics) 1995年 967卷 V-VI页

作者： Bowen, Jonathan Hincbey, Mike Oxford University Computing Laboratory Wolfson Building Parks Road Oxford United Kingdom Real-Time Computing Laboratory New Jersey Institute of Technology University Heights NewarkNJ United States Department of Computer Science and Information Systems University of Limerick Plassey Technological Park Castletroy Limerick Ireland

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DESIGN AND EVALUATION OF EFFECTIVE LOAD SHARING IN DISTRIBUTED real-time SYSTEMS

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IEEE TRANSACTIONS ON PARALLEL AND DISTRIBUTED SYSTEMS 1994年第7期5卷 704-719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 Department of Electrical and Computer Engineering University of Wisconsin Madison WI USA Real-Time Computing Laboratory Department of Electrical Engineering and Computer Science University of Michigan Arbor MI USA

In a distributed real-time system, uneven task arrivals temporarily overload some nodes and leave others idle or underloaded. Consequently, some tasks may miss their deadlines even if the overall system has the capacity to meet the deadlines of all tasks. An effective load-sharing (LS) scheme is proposed as a solution to this problem. Upon arrival of a task at a node, the node determines whether the node can complete the task in time under the minimum-laxity first-served policy. If the task cannot be guaranteed, or if guarantees of some other tasks are to be violated as a result of the addition of this task to the existing schedule, the node looks up the list of loss-minimizing decisions and determines the best node among a set of nodes in its physical proximity, called its buddy set, to which the task(s) may be transferred. This list of decisions is periodically updated using Bayesian decision analysis and prior/posterior state distributions. These probability distributions are derived from the information collected via time-stamped state-region change broadcasts within each buddy set. By characterizing the inconsistency between a node's ''observed'' state and the corresponding true state with prior and posterior distributions, the node can first estimate the states of other nodes, and then use them to reduce the probability of transferring a task to an ''incapable'' node. Moreover, the use of prior and posterior distributions and Bayesian analysis has made the proposed scheme robust to the variation of design parameters that usually require fine-tuning for adaptive LS. The performance of the proposed scheme is evaluated via simulation, along with five other schemes: no LS, LS with state probing, LS with random selection, LS with focused addressing, and perfect LS. The proposed scheme is shown to outperform all but perfect 1,S scheme in meeting task deadlines and tolerating the delays in state collection and task transfer. The impact of statistical fluctuations in

关键词： DEADLINES real-time SYSTEMS LOAD SHARING LOCATION AND TRANSFER POLICIES BAYESIAN DECISION THEORY PERFORMANCE EVALUATION

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FAULT-TOLERANT CLOCK SYNCHRONIZATION IN LARGE MULTIcomputer SYSTEMS

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IEEE TRANSACTIONS ON PARALLEL AND DISTRIBUTED SYSTEMS 1994年第9期5卷 912-923页

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

The cost of synchronizing a multicomputer increases with system size. For large multicomputers, the time and resources spent to enable each node to estimate the clock value of every other node in the system can be prohibitive. We show how to reduce the cost of synchronization by assigning each node to one or more groups, then having each node estimate the clock values of only those nodes with which it shares a group. Since each node estimates the clock value of only a subset of the nodes, the cost of synchronization can be significantly reduced. We also provide a method for computing the maximum skew between any two nodes in the multicomputer, and a method for computing the maximum time between synchronizations. We also show how the fault tolerance of the synchronization algorithm may be determined.

关键词： CLOCK SYNCHRONIZATION CLOCK SKEW CLOCK DRIFT FAULT TOLERANCE MULTIcomputer SYSTEMS

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FAULT-TOLERANT ROUTING IN MESH ARCHITECTURES

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IEEE TRANSACTIONS ON PARALLEL AND DISTRIBUTED SYSTEMS 1994年第11期5卷 1225-1232页

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

It is important for a distributed computing system to be able to route messages around whatever faulty links or nodes may be present. We present a fault-tolerant routing algorithm that assures the delivery of every message as long as there is a path between its source and destination;The algorithm works on many common mesh architectures such as the torus and hexagonal mesh. The proposed scheme can also detect the nonexistence bf path between a pair of nodes in a finite amount of time. Moreover, the scheme requires each node in the system to know only the state (faulty or not) of each of its own links. The performance of the routing scheme is simulated for both square and hexagonal meshes while varying the physical distribution of faulty components. It is shown that a shortest path between the source and destination of each message is taken with a high probability, and, if a path exists, it is usually found very quickly.

关键词： HEXAGONAL MESH DISTRIBUTED SYSTEMS ROUTING FAULTY LINKS CYCLES INCISIONS

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SUPRA-RPC - SUBPROGRAM PARAMETERS IN REMOTE PROCEDURE CALLS

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SOFTWARE-PRACTICE & EXPERIENCE 1994年第1期24卷 27-49页

作者： STOYENKO, AD Real-Time Computing Laboratory Department of Computer and Information Science New Jersey Institute of Technology University Heights Newark New Jersey 07102 U.S.A.

Remote-procedure calls (RPCs) allow distributed, high-level language programs to communicate and synchronize in the usual manner via subprogram calls. One of the great challenges in RPC research is to preserve the traditional call semantics despite the distribution and heterogeneity of the new environment. The main contribution of SUPRA-RPC is in addressing the passing of subprograms as RPC parameters. In doing so, SUPRA overcomes a number of technical difficulties, stemming from scoping, side-effects and other sources. Since supporting subprogram RPC parameters is harder than supporting nonsubprogram RPC parameters, the three (of six) components of the SUPRA architecture extend in novel ways the traditional functionality found in their counterparts in other RPC systems. The SUPRA stub generator extracts information not only from remote entry interfaces, but from any scope potentially referenced by a subprogram passed as an RPC parameter. In addition to the usual call- and accept-stubs and the marshaling and unmarshaling routines, the generator constructs out-of-scope access stubs, callback' and callback-handling-stubs, and modified parameter subprograms and others. The SUPRA run-time support manages a run-time symbol table to keep track of referencing environments and out-of-scope objects. When an out-of-scope object is unavailable for access or execution on the server, the object is reached by a synchronous, 'under-the-covers' callback. The SUPRA process management supports servers with independent threads of control, manages (possibly nested) callbacks and pools of callback handler threads, and maintains correct identification of thread-initiated calls or callbacks. A SUPRA prototype has been implemented on Sun Unix workstations. The prototype supports C, C++ and CommonLisp programs. A prototype graphical demonstration has been implemented as well, that represents RPC concepts in terms of common life objects and situations.

关键词： REMOTE PROCEDURE CALLS PASSING SUBPROGRAMS AS PARAMETERS PRESERVING HIGH-LEVEL LANGUAGE SEMANTICS DISTRIBUTED PROGRAMS STUB GENERATION CALLBACKS

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