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2006 13th GI/ITG Conference on Measuring, Modelling and Evaluation of computer and Communication systems, MMB 2006

作者： Bazan, Peter Bolch, Gunter German, Reinhard Department of Computer Networks and Communication Systems Friedrich-Alexander University Erlangen-Nümberg Germany Department of Distributed Systems and Operating Systems Friedrich-Alexander University Erlangen-Nilrnberg Germany

ISBN: (纸本)9783800729456

WinPEPSY-QNS is a tool for the easy construction of queueing network models and the evaluation of the performance measures. A graphical and a textual editor can be used for the construction process. The performance measures of the models can be derived by several analysis methods. For product-form networks the mean value analysis (MVA), the method of Jackson, and the method for BCMP networks are implemented. For non-product-form networks the methods of Marie or Chylla can be used. The state space based analysis is provided by a discrete event simulation and solvers for continuous time Markov chains. Some important non-Markovian distributions can be approximated by phase-type distributions. For large Markov chains an efficient solver has been implemented, based on multi-valued decision diagrams and a new approximation method for the stationary analysis.

关键词： Discrete event simulation

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i-DBF: an Improved Bloom Filter Representation Method on Dynamic Set

i-DBF: an Improved Bloom Filter Representation Method on Dyn...

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International Conference on Grid and Cooperative Computing Workshops (GCCW)

作者： Jiacong Wang Mingzhong Xiao Jing Jiang Bonan Min Computer Networks and Distributed Systems Laboratory Peking University China

Bloom filter is a simple space-efficient randomized data structure for representing a set in order to support membership queries, which uses an m-bit array to represent a data set. Dynamic bloom filter (DBF) can support concisely representation and approximate membership queries of dynamic set instead of static set. It has been proved that DBF not only possess the advantage of standard bloom filter, but also has better features when dealing with dynamic set. But DBF also has a disadvantage: the addition operation which mapped element x into bloom filter s will become no sense, if some of the first s-1 bloom filters have already responded that element x is in set A with some false positive probability. We point out this shortcoming and improve the addition operation with a new algorithm. We call this improved dynamic bloom filter i-DBF. Finally, we prove that this i-DBF has better performance both in the storage space and in the false positive probability

关键词： Data structures Peer to peer computing Costs computer networks Laboratories Protocols Information filtering Information filters Bandwidth Grid computing

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MMC01-2: A Replica-Conscious Load Balancing Strategy for Large-Scale Multimedia Storage systems

MMC01-2: A Replica-Conscious Load Balancing Strategy for Lar...

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IEEE Globecom 2006

作者： Zeng Zeng Bharadwaj Veeravalli Computer Networks and Distributed Systems Laboratory National University of Singapore Singapore

In distributed multimedia storage systems where client requests for different multimedia objects may have different demands, placement and replication of the objects is an important factor, as it may result in an imbalance in server loading across the system. Replica management and load balancing is all the more a crucial issue for large-scale multimedia systems. We design and analyze a heuristic static strategy to determine the placement, number of replicas of the objects, and balance the client requests among the servers, to minimize the average waiting time (AWT) of the requests. Our strategy exploits clever virtual routing technique to strike a balance among the servers for load balancing. We validate the performance via rigorous simulations with respect to several influencing factors and compare with a system that uses hashing function only for load balancing.

关键词： Load management Large-scale systems Multimedia systems Network servers Streaming media Web server computer networks Laboratories Bandwidth Routing

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A NEW APPROACH FOR MODELING LOCAL SELECTIVE CONNECTIVITY AND MAINTAINING ISOLATED REGIONS INAD HOCnetworks

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International Journal on Wireless & Optical Communications 2006年第1期3卷 23-47页

作者： M. BORSCHBACH Chair of Computer Networks and Distributed Systems University of Chemnitz D-09107 Strasse der Nationen 62 Germany

The major prerequisites for successful wireless ad hoc networking are an almost homogeneous distribution of a non-trivial number of nodes and the determination of an almost ideal selective connectivity of these nodes in the network. To give a basic characterization of network connectivity, an ad hoc network model based on planar graphs is introduced. According to this underlying mathematical network description, the features of homogeneous connectivity for ad hoc networks are defined. The network model definitions of a connected, a simple connected, a strict connected, a multiple connected and a strong connected network have an iterative foundation on the meta set of the formal network description and the fulfilled local connectivity requirements. The degree of connectivity of each node and the intensity of connectivity of the network itself is maintained by the multiple paths existing at a time. Due to a specific physical layer ratio of wireless capacity utilization and the average number of independent paths, a condition of isolation provides the opportunity to maintain isolated areas in any given ad hoc network distribution. To support identified isolated regions is a main goal of a hybrid transfer network. According to the common underlying mathematical model of ad hoc networks introduced, a selective network model is defined to analyze local node connectivity. Based on a system architecture with a predetermined number of independent and simultaneous links of each network node, the different optimization degrees of the selection of neighbors are presented. A higher relaying efficiency gives the main opportunity for an ad hoc net to be an essential part of a future networking system. The efficiency of a selective network topology is compared to pure range controlled topology.

关键词： ad hoc network models topology control modeling inhomogeneous distributions ideal local node connectivity

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Fault-Tolerant Scheduling of Independent Tasks in Computational Grid

Fault-Tolerant Scheduling of Independent Tasks in Computatio...

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International Conference on Communication systems

作者： Qin Zheng Bharadwaj Veeravalli Chen-khong Tham Computer Networks and Distributed Systems Laboratory (CNDS) Department of Electrical and Computer Engineering National University of Singapore Singapore

Primary-backup approach is a common approach used for fault tolerance wherein each task has a primary copy and a backup copy on two different processors. The backup copy can overlap with other backup copies on the same processor, as long as their corresponding primary copies are scheduled on different processors. In this paper, we consider the problem of fault-tolerant scheduling of independent tasks using primary-backup approach with backup overlapping in computational grid. A fault-tolerant scheduling algorithm is developed which minimizes replication cost for backup copy by taking into account backup overlapping in cost function. A centralized scheme and a distributed scheme are developed for the proposed algorithm and their performance are studied through simulation experiments

关键词： Fault tolerance Processor scheduling Grid computing Fault tolerant systems Cost function distributed computing Scheduling algorithm computer networks Hardware Intelligent networks

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Network-based Caching Algorithms for Reservation-based Multimedia systems

Network-based Caching Algorithms for Reservation-based Multi...

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International Conference on Grid and Cooperative Computing (GCC)

作者： Bharadwaj Veeravalli Zeng Zeng Neeraj Gupta Guoguang Jia Computer Networks and Distributed Systems Laboratory National University of Singapore Singapore School of Computer and Communication Hunan University Changsha Hunan China

As streaming video over the Internet becomes increasingly popular, cost-effective caching of these large multimedia documents has become of utmost importance. For large media objects, such as a 2-hour video, treating the whole video as a single Web object for caching is not appropriate. The paper presents reservation-based caching algorithms to evaluate a segment-based buffer management approach for off-line scheduling and caching in polynomial time. The cache admission and replacement policies decide when, where and for how long videos will be cached. Requests for videos are available a priori

关键词： Multimedia systems Costs Streaming media Network servers Bandwidth Motion pictures Cache storage computer networks Processor scheduling High-speed networks

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Medium Access Control with Adjustable Sleeps for Wireless Sensor networks

Medium Access Control with Adjustable Sleeps for Wireless Se...

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IEEE Symposium on computers and Communications (ISCC)

作者： C.K. Nguyen A. Kumar Mobile Information Networks & Distributed Systems MINDS Lab Computer Engineering & Computer Science CECS Department University of Louisville Louisville KY USA

The paper proposes a throughput and energy-aware medium-access-control protocol for wireless sensor networks. The proposed approach provides a sleeping-time adjustment scheme to flexibly adjust the sleep time to reduce the wasted energy in a low-traffic network and increase the throughput in a high-traffic network. The sleeping and waking durations are determined using time counters rather than time slots. A waking-time sharing scheme is responsible for establishing the common waking time among a group of neighbors for group communication. The proposed protocol solves the energy inefficiency caused by idle listening. Simulation experiments have been performed to demonstrate the effectiveness of the proposed approach compared to some other energy-aware medium-access-control protocols.

关键词： Media Access Protocol Sleep Wireless sensor networks Throughput Access protocols Energy consumption Scheduling Wireless application protocol Frequency Time division multiple access

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Design and Performance Evaluation of Fail-over and Recovery Strategies for Large-Scale Multimedia Storage systems

Design and Performance Evaluation of Fail-over and Recovery ...

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IEEE International Conference on networks

作者： Zeng Zeng Bharadwaj Veeravalli Jaideep Srivastava Computer Networks and Distributed Systems Laboratory National University of Singapore Singapore Department of Computer Science and Engineering University of Minnesota Minneapolis MN USA

ISBN: (纸本)0780397460

Failure-over and recovery is a crucial issue for large-scale multimedia storage system (MSS). In the literature, there are two fail-over policies: active-standby fail-over and active-active fail-over. In this paper, we adopt an active-active policy and design two heuristic algorithms to determine the number and the placement of the object replicas among the multimedia servers. One is named as "minimum average waiting time" (MAWT) strategy, in which we will choose the server to store an object replica according to an optimal solution, and the other algorithm is named as "one of the best two choices" (OBTC) strategy, in which we will randomly choose one out of the first two best choices according to an optimal solution. We analyze their performance in the cases when the system runs normally and when some failure occurs. Via rigorous simulations, we find that when the system is running normally (without failures), MAWT performs better than OBTC and when some server fails, OBTC performs much better than MAWT

关键词： Large-scale systems Multimedia systems Network servers Information retrieval File servers computer science Design engineering computer networks Laboratories Algorithm design and analysis

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A wireless-sensor-network energy-efficient medium-access-control protocol with overhearing avoidance

A wireless-sensor-network energy-efficient medium-access-con...

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Consumer Communications and Networking Conference, CCNC IEEE

作者： C.K. Nguyen A. Kumar Mobile Information Networks & Distributed Systems MINDS Lab Computer Engineering & Computer Science CECS Department University of Louisville Louisville KY USA

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WinPEPSY-QNS - Performance Evaluation and Prediction System for Queueing networks

WinPEPSY-QNS - Performance Evaluation and Prediction System ...

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13th GI/ITG Conference - Measuring, Modelling and Evaluation of computer and Communication systems

作者： Peter Bazan Gunter Bolch Reinhard German Department of Computer Networks and Communication Systems Friedrich-Alexander University Erlangen-Nürnberg Germany Department of Distributed Systems and Operating Systems Friedrich-Alexander University Erlangen-Nürnberg Germany

关键词： Throughput

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