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International Conference on Distributed computing Systems Workshop

作者： Hsin-hung Lin Chih-wen Hsueh Chung-hung Chen Real-Time Systems Laboratory Department of Computer Science and Information Engineering National Chung Cheng University Chiayi Taiwan

ISBN: (纸本)0769519210

Rapid prototyping is an automated manufacturing process that quickly builds physical models from CAD files of three-dimensional prototypes. It dramatically speeds up design and manufacturing processes and substantially reduces the production cost. With the advanced Web technologies, rapid prototyping manufacturing systems can be further integrated and more effectively utilized. We have designed a distributed web platform where users can design prototypes, simulate manufacturing, and issue ordering requests for real manufacturing through browser interfaces. However, an improper scheduling approach may degrade system utilization and throughput significantly. To solve this problem, we propose a real-time scheduling approach to maximize system utilization and minimize the average response time with the best effort. Using this approach, new requests can be accepted dynamically and all accepted requests can be finished before deadlines. We show that the scheduling overhead can be neglected and the average response time is very close to the optimal solution. With the proposed scheduling approach, the Web rapid prototyping platform is able to fully utilize Web resources for rapid prototyping manufacturing and the quality of service is significantly improved.

关键词： Job shop scheduling Prototypes Manufacturing processes Virtual manufacturing Delay Design automation Process design Production Costs Manufacturing systems

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Improving wait-free algorithms for interprocess communication in embedded real-time systems

Improving wait-free algorithms for interprocess communicatio...

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2002 USENIX Annual Technical Conference

作者： Huang, Hai Pillai, Padmanabhan Shin, Kang G. Real-Time Computing Laboratory Department of Electrical Engineering and Computer Science University of Michigan Ann ArborMI48109-2122 United States

ISBN: (纸本)1880446006

Concurrency management is a basic requirement for interprocess communication in any multitasking system. This usually takes the form of lock-based or other blocking algorithms. In real-time and/or time-sensitive systems, the less-predictable timing behavior of lock-based mechanisms and the additional task-execution dependency make synchronization undesirable. Recent research has provided non-blocking and wait-free algorithms for interprocess communication, particularly in the domain of single-writer, multiple-reader semantics, but these algorithms typically incur high costs in terms of computation or space complexity, or both. In this paper, we propose a general transformation mechanism that takes advantage of temporal characteristics of the system to reduce both time and space overheads of current single-writer, multiple-reader algorithms. We show a 17–66% execution time reduction along with a 14–70% memory space reduction when three wait-free algorithms are improved by applying our transformation. We present three new algorithms for wait-free, single-writer, multiple-reader communication along with detailed performance evaluation of nine algorithms under various experimental conditions. © 2002 USENIX Association. All rights reserved.

关键词： Locks (fasteners)

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Multicast video-on-demand services

Multicast video-on-demand services

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作者： Ma, Huadong Shin, Kang G. College of Computer Science and Technology Beijing University of Posts and Telecomm Beijing 100876 China Real-Time Computing Laboratory Department of EECS University of Michigan Ann Arbor MI 48109-2122 United States

The server's storage I/O and network I/O bandwidths are the main bottleneck of VoD service. Multicast offers an efficient means of distributing a video program to multiple clients, thus greatly improving the VoD performance. However, there are many problems to overcome before development of multicast VoD systems. This paper critically evaluates and discusses the recent progress in developing multicast VoD systems. We first present the concept and architecture of multicast VoD, and then introduce the techniques used in multicast VoD systems. We also analyze and evaluate problems related to multicast VoD service. Finally, we present open issues on multicast VoD as possible future research directions.

关键词： Video on demand

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Layer-4 service differentiation and resource isolation

Layer-4 service differentiation and resource isolation

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IEEE Symposium on real-time and Embedded Technology and Applications

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

While the differentiated services (DiftServ) infrastructure is scalable and robust in providing network quality of service (QoS), there are serious drawbacks with the services provided by DiffServ: (1) the services are coarse-grained and one-way only; (2) no service differentiation and resource isolation are provided to meta-data packets such as TCP SYN and ACK packets. Moreover the coarse-grained service differentiation and the lack of resource isolation at IP routers exposes its vulnerability to distributed denial of service (DDoS) attacks. Based on the concept of layer-4 service differentiation and resource isolation, where the transport-layer information is inferred from the IP headers and used for packet classification and resource management, we present a scalable fine-grained DiffServ (sf-DiffServ) architecture that provides fine-grained service differentiation and resource isolation among thinner behavior aggregates (BAs). The sf-DiffServ architecture consists of a fine-grained QoS classifier and an adaptive weight-based resource manager at IP routers. A two-stage packet classification mechanism is devised to decouple the fine-grained QoS lookup from the routing lookup at core routers. Due to its scalable QoS support for TCP control segments, sf-DiffServ supports bi-directional differentiated services for TCP sessions. Most importantly, the fine-grained resource isolation provided inside the sf-DiffServ is a powerful built-in protection mechanism to counter DDoS attacks, reducing the vulnerability of the Internet to DDoS attacks.

关键词： Quality of service TCPIP computer crime Diffserv networks Resource management Robustness Aggregates Routing Bidirectional control Protection

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Analysis of combined adaptive bandwidth allocation and admission control in wireless networks

Analysis of combined adaptive bandwidth allocation and admis...

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

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

An analytical model is developed for cellular networks with a combined adaptive bandwidth allocation and traffic-restriction mechanism. Instead of focusing only on the bandwidth utilization and forced-termination probability, we derive two important quality-of-service (QoS) metrics, degradation ratio and upgrade/degrade frequency. We show numerically that these two metrics must be taken into account in order to support the QoS specified by each client. The effects of system loads and clients' mobility on system performance are also investigated. Even under the various distributions of mobility, the simulation results are shown to match our analytical results, implying the applicability of our analytical model to more general cases.

关键词： Programmable control Adaptive control Channel allocation Admission control Wireless networks Analytical models Degradation Land mobile radio cellular systems Communication system traffic control Traffic control

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Measurement of OS services and its application to performance modeling and analysis of integrated embedded software

Measurement of OS services and its application to performanc...

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IEEE Symposium on real-time and Embedded Technology and Applications

作者： S. Wang S. Kodase K.G. Shin D.L. Kiskis Real-Time Computing Laboratory Department of Electrical Engineering and Computer Science University of Michigan Ann Arbor MI USA

Performance analyses for embedded software construction with existing components require knowledge of performance characteristics of both application software and operating system (OS) services, especially those services that are critical for real-time applications. Since end users normally do not control the structure and implementation of OS services, but have to use them to meet the system-level performance constraints, it is essential and critical to characterize the performance of OS services with measurements. As such measurements are taken for performance analysis, not for comparison, the measurement methods should be different from those traditionally, used for comparison. In this paper we present an end-to-end method for measuring the performance of timing and scheduling services in selected real-time OSs for the performance modeling and analysis. The proposed method takes the factors of both OS implementations and application configurations into account to obtain the measured performance close to what applications will experience at runtime. The results have shown that the performance characteristics of OS services can be measured without instrumenting the kernel source code, and hence, can be reused for the analysis of a family of applications.

关键词： Software measurement Application software Performance analysis Embedded software Operating systems real time systems Control systems Timing Runtime Instruments

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6.2.4 Investigating Risks in Systems Engineering Tool Data Exchange

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INCOSE International Symposium 2001年第1期11卷 316-323页

作者： Herzog, Erik Törne, Anders Real-Time Systems Laboratory Department of Computer and Information Science Linköpings Universitet Sweden

Data exchange capabilities are generally regarded as a desirable (but in many cases absent) property of systems engineering tools. While such capabilities are desirable it is also the case that there is a substantial risk that tool data exchange impose modifications to the data transferred. In this paper we illustrate how modifications are introduced based on the capabilities of individual tools, present an analysis of potentially adversary effects of data exchanges and discuss measures for preventing data exchange related errors from being introduced in a specification. The paper also discusses requirements for data exchange information models for heterogeneous domains to support representation of multiple semantic variants of basic concepts. Aspects of the emerging ISO standard AP-233 is evaluated against these requirements and an example is presented to illustrate the point. © 2001 The Authors.

关键词： Electronic data interchange

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Design and evaluation of routing schemes for dependable real-time connections

Design and evaluation of routing schemes for dependable real...

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International Conference on Dependable Systems and Networks (DSN)

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

Dependability of service (DoS) has become an important requirement for real-time applications, such as remote medical services, business-critical network meetings and command-and-control applications. The Dependable real-time Protocol (DRTP), in which each dependable real-time connection is realized with one primary and one or more backup channels, has been shown to be an effective way of providing DoS. How to route both primary and backup channels for each dependable real-time connection is of vital importance to the success of failure recovery and to overhead reduction in providing DoS. In this paper, we propose and evaluate three different schemes for routing the primary and backup channels of each dependable real-time connection. Specifically, we present methods based on link-state information and bounded flooding to discover routes for the primary and backup channels while satisfying the required quality of service (QoS). The costs of the link-state and flooding algorithms are reduced significantly by using the fact that the probability of success in failure recovery can be estimated with simple link-state information, and by bounding the flooded region within an ellipse with the two communication end-points as loci. Our in-depth simulations have shown that the proposed routing schemes are highly effective, providing a fault tolerance of 87% or higher with a network capacity overhead of less than 85%.

关键词： Routing Floods Streaming media Delay Medical services Quality of service Fault tolerance Throughput Laboratories Electronic mail

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Reconfigurable software for open architecture controllers

Reconfigurable software for open architecture controllers

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IEEE International Conference on Robotics and Automation (ICRA)

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

ISBN: (纸本)0780365763

We present an architecture that supports reconfigurable software construction. In this architecture, the controller software consists of a set of well-defined components and a set of behavior specifications. Each component is modeled with event-based external interfaces, a control logic driver and service protocols. Behaviors of components and their integration are modeled as finite state machines and nested finite state machines. The behaviors of software can be specified in Control Plan programs and executed by control logic drivers at run-time. Such software supports executable code-level reconfiguration as well as remote behavioral reconfiguration. Reconfiguration with heterogeneous implementations and vendor-neutral products is also supported. Our evaluation of the motion control software for a milling machine controller demonstrated that the software constructed with this architecture has high reconfigurability and low development and maintenance costs.

关键词： computer architecture Software maintenance Reconfigurable logic Protocols Control systems Application software Communication system control Machine control Automata Motion control

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Second-order rate-control based transport protocols

Second-order rate-control based transport protocols

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International Conference on Network Protocols

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

ISBN: (纸本)0769514294

We propose an efficient flow and error control scheme for high-throughput transport protocols by using a second-order rate control, called the /spl alpha/-control, and a new sliding-window scheme for error control. The /spl alpha/-control minimizes the packet retransmissions by adjusting the rate-gain parameter to the variations in the number and round-trip times (RTTs) of cross-traffic flows that share the bottleneck. Using selective retransmission, the sliding-window scheme guarantees lossless transmission. By applying the /spl alpha/-control, the proposed scheme can drive the flow-controlled system to a retransmission-less equilibrium state. Using the fluid analysis, we establish the flow-control system model, obtain the greatest lower bound for the target buffer occupancy, and derive closed-form expressions for packet losses, loss rate, and link-transmission efficiency. We prove that the /spl alpha/-control is feasible and optimal linear control in terms of efficiency and fairness. Also presented are the extensive simulation results that confirm the analytical results, and demonstrate the superiority of the proposed scheme to others in dealing with the variations of cross-traffic flows sharing the same bottleneck and their RTTs, controlling packet losses/retransmissions, and achieving buffer-usage fairness as well as high throughput.

关键词： Transport protocols Throughput Error correction Propagation losses Transmitters Laboratories Closed-form solution Optimal control Fluid flow control Internet

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