8 research outputs found
Queueing networks: solutions and applications
During the pasttwo decades queueing network models have proven to be a versatile tool for computer system and computer communication system performance evaluation. This chapter provides a survey of th field with a particular emphasis on applications. We start with a brief historical retrospective which also servesto introduce the majr issues and application areas. Formal results for product form queuenig networks are reviewed with particular emphasis on the implications for computer systems modeling. Computation algorithms, sensitivity analysis and optimization techniques are among the topics covered. Many of the important applicationsof queueing networks are not amenableto exact analysis and an (often confusing) array of approximation methods have been developed over the years. A taxonomy of approximation methods is given and used as the basis for for surveing the major approximation methods that have been studied. The application of queueing network to a number of areas is surveyed, including computer system cpacity planning, packet switching networks, parallel processing, database systems and availability modeling.Durante as últimas duas décadas modelos de redes de filas provaram ser uma ferramenta versátil para avaliação de desempenho de sistemas de computação e sistemas de comunicação. Este capítulo faz um apanhado geral da área, com ênfase em aplicações. Começamos com uma breve retrospectiva histórica que serve também para introduzir os pontos mais importantes e as áreas de aplicação. Resultados formais para redes de filas em forma de produto são revisados com ênfase na modelagem de sistemas de computação. Algoritmos de computação, análise de sensibilidade e técnicas de otimização estão entre os tópicos revistos. Muitas dentre importantes aplicações de redes de filas não são tratáveis por análise exata e uma série (frequentemente confusa) de métodos de aproximação tem sido desenvolvida. Uma taxonomia de métodos de aproximação é dada e usada como base para revisão dos mais importantes métodos de aproximação propostos. Uma revisão das aplicações de redes de filas em um número de áreas é feita, incluindo planejamento de capacidade de sistemas de computação, redes de comunicação por chaveamento de pacotes, processamento paralelo, sistemas de bancos de dados e modelagem de confiabilidade
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Decomposition of general queueing network models. An investigation into the implementation of hierarchical decomposition schemes of general closed queueing network models using the principle of minimum relative entropy subject to fully decomposable constraints.
Decomposition methods based on the hierarchical partitioning of
the state space of queueing network models offer powerful evaluation
tools for the performance analysis of computer systems and
communication networks. These methods being conventionally
implemented capture the exact solution of separable queueing network
models but their credibility differs when applied to general queueing
networks. This thesis provides a universal information theoretic
framework for the implementation of hierarchical decomposition
schemes, based on the principle of minimum relative entropy given
fully decomposable subset and aggregate utilization, mean queue
length and flow-balance constraints. This principle is used, in
conjuction with asymptotic connections to infinite capacity queues,
to derive new closed form approximations for the conditional and
marginal state probabilities of general queueing network models. The
minimum relative entropy solutions are implemented iteratively at
each decomposition level involving the generalized exponential (GE)
distributional model in approximating the general service and
asymptotic flow processes in the network. It is shown that the
minimum relative entropy joint state probability, subject to mean
queue length and flow-balance constraints, is identical to the exact
product-form solution obtained as if the network was separable. An
investigation into the effect of different couplings of the resource
units on the relative accuracy of the approximation is carried out,
based on an extensive experimentation. The credibility of the method
is demonstrated with some illustrative examples involving
first-come-first-served general queueing networks with single and
multiple servers and favourable comparisons against exact solutions
and other approximations are made