We discuss an adaptive flow control mechanism for the Swift/RAID distributed file system. Our goal is to achieve near-optimal performance on heterogeneous networks where available load capacity varies due to other net...
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We discuss an adaptive flow control mechanism for the Swift/RAID distributed file system. Our goal is to achieve near-optimal performance on heterogeneous networks where available load capacity varies due to other network traffic. the original Swift/RAID prototype used synchronous communication, achieving throughput considerably less than available network capacity. We designed and implemented an adaptive flow control mechanism that provides greatly improved performance. Our design uses a simple automatic repeat request (ARQ) go back N protocol coupled withthe congestion avoidance and control mechanism developed for the Transmission Control Protocol (TCP). the Swift/RAID implementation contains a transfer plan executor to isolate all of the communications cede from the rest of Swift. the adaptive flow control design was implemented entirely in this module. Results from experimental data show the adaptive design achieving an increase in throughput for reads from 671 KB/s for the original synchronous implementation to 927 KB/s (a 38% increase) for the adaptive prototype, and an increase from 375 KB/s to 559 KB/s (a 49% increase) in write throughput.
the international Space Station will be the most complex and expensive spacecraft ever to fly. Making best use of this costly resource requires tools to assist the planning of operations, and to automate the execution...
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the international Space Station will be the most complex and expensive spacecraft ever to fly. Making best use of this costly resource requires tools to assist the planning of operations, and to automate the execution of operational procedures. these capabilities, which operate in close association with each other, are known as "plans and procedures". the "plans" system maintains and executes the "onboard short term plan", an integrated schedule that includes all space station manual and automated activities. this software supports a graphic display presenting the plan to the crew; allows the ground and onboard crew to add, delete and edit activities; tracks the status of each activity; and automatically initiates automated procedures. the "procedures" capability involves procedure executors installed in various space station computers. this software provides the ability to create on the ground, and execute onboard, automated procedures to supplement the human role in operating the spacecraft and its payloads.
In this paper, we study the positive impact that the availability of 'Sense of Direction' has on the message complexity of the Election problem in arbitrary networks of processors. We present a θ(n log n) sol...
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ISBN:
(纸本)0818658401
In this paper, we study the positive impact that the availability of 'Sense of Direction' has on the message complexity of the Election problem in arbitrary networks of processors. We present a θ(n log n) solution;without sense of direction, this problem requires Ω(e + n log n) messages where e is the number of communication links. this result confirms and extends the evidence on the impact of sense of direction which, up to new, was established only for specific classes of topologies.
this paper presents a system of methods and models for evaluating the performability, reliability, and survivability of a communication network. All proposed models and methods are shown to be interdependent by way of...
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this paper presents a system of methods and models for evaluating the performability, reliability, and survivability of a communication network. All proposed models and methods are shown to be interdependent by way of indexes and parameters of the basic network properties. Indexes for these network properties are found for each message-exchanging terminal pair and for the entire network. Steady-state availability, MTBF (mean time between failures), and MTTR (mean time to repair) are computed for reliability analysis of the network with limited repair. Survivability indexes are found for the network exposed to multiple external (adverse) influences that cause a gradual structural degradation of the network. Models are proposed for the performability evaluation of unreliable virtual circuit network X.25/X.75 with routing adapted to network element failures. Some numerical results of comparative analysis of network performability for adaptive and static routings are presented.
this paper develops a unified framework for reasoning about timing correctness of packet-switched networks. the unification is in the form of a set of consistent scheduling models for a variety of network architecture...
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this paper develops a unified framework for reasoning about timing correctness of packet-switched networks. the unification is in the form of a set of consistent scheduling models for a variety of network architectures and protocols. the unification is important as it allows heterogeneous network types to be analyzed using a consistent methodology and facilitates scheduling over multihop networks where each link is a different type of network. To demonstrate the framework, a scheduling model for a dual-link network, IEEE 802.5 token ring, and FDDI, is presented. the use of this framework to select paths in multi-hop networks is also demonstrated.< >
this paper presents a system of methods and models for evaluating the performability, reliability, and survivability of a communication network. All proposed models and methods are shown to be interdependent by way of...
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this paper presents a system of methods and models for evaluating the performability, reliability, and survivability of a communication network. All proposed models and methods are shown to be interdependent by way of indexes and parameters of the basic network properties. Indexes for these network properties are found for each message-exchanging terminal pair and for the entire network. Steady-state availability, MTBF (mean time between failures), and MTTR (mean time to repair) are computed for reliability analysis of the network with limited repair. Survivability indexes are found for the network exposed to multiple external (adverse) influences that cause a gradual structural degradation of the network. Models are proposed for the performability evaluation of unreliable virtual circuit network X.25/X.75 with routing adapted to network element failures. Some numerical results of comparative analysis of network performability for adaptive and static routings are presented.< >
the goal of the paper is to describe run time efficiency of distributed computing environments. Six tools: PVM, P4, ANSA, SR, Strand, and Linda were chosen and investigated because they represent different approaches ...
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the goal of the paper is to describe run time efficiency of distributed computing environments. Six tools: PVM, P4, ANSA, SR, Strand, and Linda were chosen and investigated because they represent different approaches to distributed programming systems construction. the experimental results of communication tests and processor farm model efficiency are presented and discussed.< >
Presents a new algorithm for distributed shared virtual memory dedicated to diskless embedded systems. In this context, we adapt an existing algorithm in order to include a page replacement mechanism. We also propose ...
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Presents a new algorithm for distributed shared virtual memory dedicated to diskless embedded systems. In this context, we adapt an existing algorithm in order to include a page replacement mechanism. We also propose a memory partition to optimize memory space use. In conclusion, our algorithm has a complexity comparable withthe initial one.< >
the media streams of a multimedia communication application may traverse through different communication channels. Because of the network delay and jitter, data in these streams sent at the same time may not arrive at...
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the media streams of a multimedia communication application may traverse through different communication channels. Because of the network delay and jitter, data in these streams sent at the same time may not arrive at a destination simultaneously. In this paper a multimedia synchronization protocol that resynchronizes the media streams is proposed. the protocol inserts extra control cells into the media streams, and aligns the cells at the receiver site. three synchronization policies, namely, the Drop-Old, the Transmit-Old and the Delayed-Transmit, are introduced to align the control cells. To satisfy the Quality of Service (QOS) specified by an application, the protocol must negotiate an appropriate QOS withthe underlying ATM network. For each of the three synchronization policies, the relationship between the specified QOS and the negotiated QOS is derived.< >
SPIDER is a network adapter that provides scalable communication support for point-to-point distributed systems. the device exports an efficient interface to the host processor, provides transparent support for depend...
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SPIDER is a network adapter that provides scalable communication support for point-to-point distributed systems. the device exports an efficient interface to the host processor, provides transparent support for dependable, time-constrained communication, and handles packet routing and switching. the communication support provided by SPIDER exploits concurrency between the independent data channels feeding the point-to-point network, and offers flexible and transparent hardware mechanisms. SPIDER allows the host to exercise fine-grain control over its operation, enabling the latter to monitor and influence data transmission and reception efficiently. In the current implementation, SPIDER interfaces to the Ironics IV-3207, a VMEbus-based 68040 card and will be controlled by x-kernel, a communication executive allowing the flexible composition of communication protocols.< >
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