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real-time Systems Symposium (RTSS)

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

We propose architectural mechanisms for structuring host communication software to provide QoS guarantees. In particular, we present and evaluate a QoS sensitive communication subsystems architecture for end hosts that provides real time communication support for generic network hardware. This architecture provides services for managing communication resources for guaranteed QoS (real time) connections, such as admission control, traffic enforcement, buffer management, and CPU and link scheduling. The design of the architecture is based on three key goals: maintenance of QoS guarantees on a per connection basis, overload protection between established connections, and fairness in delivered performance to best effort traffic. Using this architecture we implement real time channels, a paradigm for real time communication services in packet switched networks. We evaluate the implementation to demonstrate the efficacy with which the architecture maintains QoS guarantees while adhering to the stated design goals. The evaluation also demonstrates the need for specific features and policies provided in the architecture.

关键词： Software quality Quality of service comput.r architecture Resource management Communication system traffic control Hardware Admission control Protection Packet switching Communication switching

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real-time decentralized control with CAN

Real-time decentralized control with CAN

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International Conference on Emerging Technologies and Factory Automation (ETFA)

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

This paper deals with two important concerns in decentralized control: (1) communication over field bus and (2) the transition from a single powerful, centralized controller to many smaller, distributed controllers. The former requires real-time network scheduling for the field bus to ensure that messages get delivered in a timely manner, while the latter requires a low-overhead real-time operating system to cater to the specific needs of distributed control. We present solutions to both of these problems in the form of a network scheduling scheme for the controller area network (CAN) field bus and the EMERALDS real-time operating system which we have designed with the needs of the decentralized control application designer in mind.

关键词： Distributed control Control systems Centralized control Communication system control Costs Robot kinematics Distributed computing Power engineering computing Laboratories Job shop scheduling

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Combined routing and scheduling of concurrent communication traffic in hypercube multicomput.rs

Combined routing and scheduling of concurrent communication ...

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International Conference on Distributed computing Systems

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

We propose and evaluate low-complexity, low-overhead schemes for distributed message scheduling and routing in binary hypercube multicomput.rs equipped with a hardware communication adapter at each node. The goal is to optimize the network performance not only for steady traffic flow, but also for concurrent bursty traffic. We comparatively evaluate the performance of different scheduling-coding combinations for several switching methods, such as message switching, circuit switching and virtual cut-through. The evaluation results have indicated that in case of heavy transient traffic, a partially-adaptive routing scheme, when combined with an appropriate message-scheduling policy, can outperform a fully-adaptive routing scheme.

关键词： Routing Hypercubes Telecommunication traffic Switching circuits Communication switching Processor scheduling Multiprocessor interconnection networks Distributed computing Laboratories Hardware

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ORCHESTRA: a probing and fault injection environment for testing protocol implementations

ORCHESTRA: a probing and fault injection environment for tes...

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International comput.r Performance and Dependability Symposium

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

Ensuring that a distributed system meets its prescribed specification is a growing challenge that confronts software developers and system engineers. Meeting this challenge is particularly important for applications with strict dependability and/or timeliness constraints. We have developed a software fault injection tool, called ORCHESTRA, for testing dependability and timing properties of distributed protocols. ORCHESTRA is based on a simple yet powerful framework, called script-driven probing and fault injection. The emphasis of this 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. Hence, the focus is on developing fault injection techniques that can be employed in studying three aspects of a target protocol: i) detecting design or implementation errors, ii) identifying violations of protocol specifications, and iii) obtaining insights into the design decisions made by the implementers.

关键词： Protocols Fault diagnosis Software systems Power engineering and energy Systems engineering and theory Application software Software tools Software testing Timing Fault detection

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Design and analysis of a WDMA protocol for passive star-coupled lightwave networks

Design and analysis of a WDMA protocol for passive star-coup...

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IEEE Annual Joint Conference: INFOCOM, IEEE comput.r and Communications Societies

作者： Chao-Ju Hou Bin Wang Ching-Chih Han Computer Engineering Division Department of Elect. and Comput. Eng. University of Wisconsin Madison WI USA Real-Time Computing Laboratory Department of Elect. Eng. and Comput. Science University of Michigan Ann Arbor MI USA

ISBN: (纸本)0818672935

Based on the POPSMAC protocol proposed in Chung-Sheng Li et al. (1993), we propose an improved medium access protocol for wavelength division multiple access (WDMA) photonic networks. Using the same set of photonic devices as in POPSMAC, the proposed protocol alleviates the drawbacks of the POPSMAC protocol, e.g., invalid data transmissions following receiver collisions and possible acknowledgement packet collisions with header/data packets, while retaining many advantages of POPSMAC. As a result, the network performance in terms of the throughput and the packet delay is improved. Analytical models based on the timing diagram analysis, the continuous-time Markov chain, and the randomization technique are developed to assess the performance of the proposed protocol. The performance is evaluated in terms of channel utilization, mean packet delay, and packet delay distribution with variations in the number of nodes, the offered traffic, the size of data packets, and the network propagation delay. Numerical results show that the proposed protocol achieves better channel utilization and incurs lower packet delays than POPSMAC.

关键词： Access protocols Propagation delay Data communication Optical receivers Throughput Analytical models Timing Performance analysis Telecommunication traffic Traffic control

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Fault injection experiments on real-time protocols using ORCHESTRA

Fault injection experiments on real-time protocols using ORC...

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IEEE International Symposim on High Assurance Systems engineering

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

The paper presents a set of experiments on real time protocols using the ORCHESTRA software fault injection environment. The paper first describes a specific implementation of ORCHESTRA for testing applications that use Unix sockets for communication. A novel feature of this tool is that it utilizes operating system support provided by real time Mach to quantify and compensate for the intrusiveness of the fault injection mechanism. The fault injection experiments which are described, tested fault tolerance and timing behavior of two target real time protocols. In addition, timing intrusiveness of ORCHESTRA was measured during the course of these experiments.

关键词： Protocols Timing Probes System testing Delay Application software Sockets Operating systems real time systems Software measurement

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A Router Architecture for real-time Point-to-Point Networks

A Router Architecture for Real-Time Point-to-Point Networks

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Annual International Symposium on comput.r Architecture, ISCA

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

Parallel machines have the potential to satisfy the large comput.tional demands of emerging real-time applications. These applications require a predictable communication network, where time-constrained traffic requires bounds on latency or throughput while good average performance suffices for best-effort packets. This paper presents a router architecture that tailors low-level routing, switching, arbitration and flow-control policies to the conflicting demands of each traffic class. The router implements deadline-based scheduling, with packet switching and table-driven multicast routing, to bound end-to-end delay for time-constrained traffic, while allowing best-effort traffic to capitalize on the low-latency routing and switching schemes common in modern parallel machines. To limit the cost of servicing time-constrained traffic, the router shares packet buffers and link-scheduling logic between the multiple output ports. Verilog simulations demonstrate that the design meets the performance goals of both traffic classes in a single-chip solution.

关键词： Traffic control Routing comput.r architecture Parallel machines Telecommunication traffic Delay Packet switching Concurrent computing Communication networks Throughput

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Testing of fault-tolerant and real-time distributed systems via protocol fault injection

Testing of fault-tolerant and real-time distributed systems ...

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International Symposium on Fault-Tolerant computing (FTCS)

作者： S. Dawson F. Jahanian T. Mitton Teck-Lee Tung 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

As software for distributed systems becomes more complex, ensuring that a system meets its prescribed specification is a growing challenge that confronts software developers. This is particularly important for distributed applications with strict dependability and timeliness constraints. This paper reports on ORCHESTRA, a portable fault injection environment for testing implementations of distributed protocols. This tool is based on a simple yet powerful framework called script-driven probing and fault injection, for the evaluation and validation of the fault-tolerance and timing characteristics of distributed protocols. The tool, which was initially developed on the real-time Mach operating system and later ported to other platforms including Solaris and SunOS, has been used to conduct extensive experiments on several protocol implementations. This paper describes the design and implementation of the fault injection tool focusing on architectural features to support portability, minimizing intrusiveness on target protocols, and explicit support for testing real-time systems. The paper also describes the experimental evaluation of two protocol implementations: a real-time audio-conferencing application on real-time Mach, and a distributed group membership service on the Sun Solaris operating system.

关键词： System testing Fault tolerant systems real time systems Protocols Operating systems Software systems Application software Fault tolerance Timing Sun

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Message transmission with timing constraints in ring networks

Message transmission with timing constraints in ring network...

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real-time Systems Symposium (RTSS)

作者： Ching-Chih Han K.G. Shin Department of Electrical Engineering Ohio State Uinversity Columbus OH USA Real-Time Computing Laboratory Department of Elect. Engineering and Computer Science University of Michigan Ann Arbor MI USA

We consider the message transmission problem in unidirectional slotted ring networks. We consider two operation modes: 1) the evacuation mode, in which all messages arrive before system initialization and no new message arrives during system operation; and 2) the continuation mode, in which new messages may arrive after system initialization. We study the performance of several message scheduling policies with respect to three performance measures: meeting all message deadlines, minimizing the maximum delay or the total length of busy periods, and minimizing the average delay. We show that the least-slack-time-first (LSF) scheduling policy is optimal in evacuation mode operation with respect to meeting all message deadlines, while no optimal scheduling policy can possibly exist for continuation mode operation. For the other two performance measures, we show that in the case when messages may be of variable lengths: 1) the farthest-destination-first (FDF) policy is optimal in terms of minimizing the maximum delay and minimizing the total length of busy periods for evacuation mode and for continuation mode operation, respectively, and 2) no optimal scheduling policy can possibly exist in terms of minimizing the average delay under either evacuation mode or continuation mode operation.

关键词： Timing Intelligent networks Length measurement Delay effects comput.r architecture Media Access Protocol Scattering Broadcasting Switches Laboratories

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computing time-DELAY AND ITS EFFECTS ON real-time CONTROL-SYSTEMS

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IEEE TRANSACTIONS ON CONTROL SYSTEMS TECHNOLOGY 1995年第2期3卷 218-224页

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

The reliability of a real-time digital control comput.r depends not only on the reliability of the hardware and software used, but also on the time delay in computing the control output, because of the negative effects of computing time delay on control system performance. For a given fixed sampling interval, the effects of computing time delay are classified into the delay and loss problems, The delay problem, occurs when the computing time delay is nonzero but smaller than the sampling interval, while the loss problem occurs when the computing time delay is greater than, or equal to, the sampling interval, i,e., loss of the control output, These two problems are analyzed as a means of evaluating real-time control systems, First, a generic analysis of the effects of computing time delay is presented along with necessary conditions for system stability, Then, we present both qualitative and quantitative analyses of the computing time delay effects on a robot control system, deriving upper bounds of the computing time delay with respect to system stability and system performance.

关键词： Delay effects real time systems Control systems Sampling methods System performance Stability analysis Digital control Hardware Software performance Performance analysis

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