Several real-timeapplications (e.g., video conferencing, remote control systems) demand guarantees on the message delivery latency. Supporting these QoS connections requires the existence of a routing mechanism, whic...
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ISBN:
(纸本)078038783X
Several real-timeapplications (e.g., video conferencing, remote control systems) demand guarantees on the message delivery latency. Supporting these QoS connections requires the existence of a routing mechanism, which computes paths that satisfy QoS delay constraints (e.g., end-to-end delays or failure recovery delays). In mobile ad hoc network, wireless links tend to frequently fail as nodes move in and out of transmission range of one another. Providing fault tolerance with QoS guarantees in such a network is challenging. the proposed new algorithm, also called a segmented backup routing (SBR), constructs a set of segmented backup paths. Each segmented backup path, protects a segment of the primary path rather than the entire path. the most important points that are made in this algorithm are two. First, one is able to identify backup paths for any selected primary path, as long as there exists a pair of node disjoint paths from source to destination. In other words, if there are two node disjoint paths, one is not forced to use either of them to be the primary path. this has the advantage that the primary path may be selected based on QoS considerations rather than a consideration of fault tolerance. the second advantage is that there are multiple backup paths, each of which protects breakdown of one or more nodes on the primary path. A backup path may be selected based on QoS considerations. In this paper, we have primarily focused on end-to-end delay as the QoS parameter. We apply our scheme to the AODV protocol.
Recognizing the need to provide end-to-end QoS for performance sensitive applications, and the need to manage such QoS provisions in the presence of diverse application QoS requirements as well as heterogeneous networ...
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ISBN:
(纸本)078038783X
Recognizing the need to provide end-to-end QoS for performance sensitive applications, and the need to manage such QoS provisions in the presence of diverse application QoS requirements as well as heterogeneous network environment, we propose an adaptive end-to-end QoS management architecture QMan, to address such issues. QMan, as one of the key components of OCTOPUS middleware, makes no presumption of the underneath QoS provisions for end-to-end QoS management, but can take advantage of such provisions if there are. QMan allows applications to exchange QoS requirements and negotiate for a suitable protocol stack configuration withthe assistance from dynamic protocol framework (DPF). During data transmission, QMan monitors QoS violations and performs QoS adaptations according to the rules defined through a combination of three possible conduits in an end-to-end fashion: network level, host level and application level. these rules are pre-determined according to application requirements or network policies and can be re-configured for customization of QoS adaptations during run-time. Performance evaluations of our implementation demonstrate the feasibility of QMan's design with satisfactory performance.
Clusters of workstations are being extensively used for solving computationally intensive scientific problems. However, there is limited support for Quality of Service (QoS) based distributed computing on commercial o...
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ISBN:
(纸本)0769520375
Clusters of workstations are being extensively used for solving computationally intensive scientific problems. However, there is limited support for Quality of Service (QoS) based distributed computing on commercial off-the-shelf (COTS) clusters. this limitation has restricted successful deployment of distributed real-time high-performance computingapplications to customized and dedicated embedded multi-processor systems. this paper describes research work that attempts to provide a cluster platform that can guarantee access to computational and communication resources to distributed applications. the authors have developed PromisQoS, an architecture that supports execution of hard real-time distributed applications on a Linux cluster while providing high-throughput and low-latency communication using Myrinet. PromisQoS consists of the following major components -- Hare, BDM-RT and Turtle. Hare is a prototype implementation of time-based QoS channels specified by the real-time Message Passing Interface (MPI/RT 1.1) standard. BDM-RT is a low-level messaging library on Myrinet that provides deterministic communication latency and bandwidth on Myrinet. Turtle, a variant of RT-Linux, is the real-time operating system that provides guaranteed computation time. this work demonstrates that it is possible to deploy hard real-time distributed applications on COTS clusters and underlines the significance of the MPI/RT API in the realm of distributed high-performance computingapplicationsthat require QoS.
Linux is gradually expanding its base in embedded system OS, especially for networking applications. In this paper Linux is used for developing a SOHO (Small Office Home Office) router with uClinux ported to S3C2510, ...
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Performance modeling of magnetic disks allows the prediction of the disk service time which is useful for on-line decision support for soft real-timeapplications. In this paper, we propose a new performance model of ...
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ISBN:
(纸本)3540219749
Performance modeling of magnetic disks allows the prediction of the disk service time which is useful for on-line decision support for soft real-timeapplications. In this paper, we propose a new performance model of disk access time to estimate the bounded disk service time. Our proposed model focuses on modeling the head positioning time to fully utilize the disk I/O bandwidth by exploiting the geometric layout of the disk. the experimental results show that our proposed model can estimate the disk service time with less than 10% error on average.
Web services, with an emphasis on open standards and flexibility, may provide benefits over existing capital markets integration practices. However, web services must first meet certain technical requirements includin...
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ISBN:
(纸本)1581136803
Web services, with an emphasis on open standards and flexibility, may provide benefits over existing capital markets integration practices. However, web services must first meet certain technical requirements including performance, security and fault-tolerance. this paper presents an experimental evaluation of SOAP performance using realistic business application message content. To get some indication of whether SOAP is appropriate for high performance capital markets systems, the results are compared with a widely used existing protocol. the study finds that, although SOAP performs relatively poorly, the difference is less than in scientific computing environments. Furthermore, we find that in realistic business applications it is possible for text-based wire formats to have comparable performance to binary, and that the text-based nature of XML is not sufficient to explain SOAP's inefficiency. this suggests that further work may enable SOAP to become a viable wire format for high performance business applications.
Increasing complexity of real-timesystems, and demands for enabling their configurability and tailorability are strong motivations for applying new software engineering principles, such as aspect-oriented and compone...
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ISBN:
(纸本)3540219749
Increasing complexity of real-timesystems, and demands for enabling their configurability and tailorability are strong motivations for applying new software engineering principles, such as aspect-oriented and component-based development. In this paper we introduce a novel concept of aspectual component-based real-time system development. the concept is based on a design method that assumes decomposition of real-timesystems into components and aspects, and provides a real-time component model that supports the notion of time and temporal constraints, space and resource management constraints, and composability. We anticipate that the successful applications of the proposed concept should have a positive impact on real-time system development in enabling efficient configuration of real-timesystems, improved reusability and flexibility of real-time software, and modularization of crosscutting concerns. We provide arguments for this assumption by presenting an application of the proposed concept on the design and development of a configurable embeddedreal-time database, called COMET. Furthermore, using the COMET system as an example, we introduce a novel way of handling concurrency in a real-time database system, where concurrency is modeled as an aspect crosscutting the system.
We have demonstrated an entire series of capacitive sensors using a multi-layer parylene/photoresist surface micromachining technology. the developed sensors are designed for total integration into parylene-based micr...
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In this paper we address the problem of testing real-time software in the functional domain. In order to achieve reproducible and deterministic test results of an entire multitasking real-time system it is essential n...
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ISBN:
(纸本)3540219749
In this paper we address the problem of testing real-time software in the functional domain. In order to achieve reproducible and deterministic test results of an entire multitasking real-time system it is essential not to only consider inputs and outputs, but also the order in which tasks communicate and synchronize with each other. We present a deterministic white-box system-level control-flow testing method for deterministic integration testing of real-time system software. We specifically address fixed priority scheduled real-timesystems where synchronization is resolved using the Priority Ceiling Emulation Protocol or offsets in time. the method includes a testing strategy where the coverage criterion is defined by the number of paths in the system control flow. the method also includes a reachability algorithm for deriving all possible paths in terms of orderings of task starts, preemptions and completions of tasks executing in a real-time system. the deterministic testing strategy allows test methods for sequential programs to be applied, since each identified ordering can be regarded as a sequential program.
Statically analyzing real-timesystems normally involves a high degree of pessimism, but it is necessary in systems requiring 100% guarantee. However, lots of less critical systems would significantly benefit from com...
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ISBN:
(纸本)3540219749
Statically analyzing real-timesystems normally involves a high degree of pessimism, but it is necessary in systems requiring 100% guarantee. However, lots of less critical systems would significantly benefit from combining such static analysis with empirical tests. Empirical tests are based on observing the system at run time and extracting information about its temporal behavior. In this sense, this paper presents a generic and extensible framework that permits the extraction of temporal properties of real-timesystems by analyzing their run-time traces. the analysis is based on event-recognition finite state machines that compute the temporal properties with a computational cost of O(1) per observed event in most of the cases. the framework is instantiated in order to extract some typical temporal properties (such as computation time or response time of tasks), which can serve as a template to define new ones. Finally, the paper also shows how the framework can be implemented on a real system, exclusively using state-of-the-art technology;in particular, the Trace and real-time Extensions of the POSIX standard.
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