Alexandre Brandwajn

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Current computer systems and communication networks tend to be highly complex, and they typically hide their internal structure from their users. Thus, for selected aspects of capacity planning, overload control and related applications, it is useful to have a method allowing one to find good and relatively simple approximations for the observed system(More)
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This paper is an attempt to cast in a unified framework several approximation techniques based on equivalence (aggre-gation) and decompositon that have been applied for the solution of queueing networks in the last decade or so. The main idea in the proposed framework is that it is possible, and useful, to view these techniques as involving two separate(More)
Queueing network models of computer systems with multiprogramming constraints generally do not possess a product-form solution in the sense of Jackson. Therefore, one is usually led to consider approximation techniques when dealing with such models. Equivalence and decomposition is one way of approaching their solution. With multiple job classes, the(More)
In this paper we consider a multi-server queue with a near general arrival process (represented as an arbitrary state-dependent Cox-ian distribution), a near general state-dependent Coxian service time distribution and a possibly finite queueing room. In addition to the dependence on the current number of customers in the system, the rate of arrivals and(More)
Following up on a recently renewed interest in computational methods for M/G/1-type processes, this paper considers an M/G/1-like system in which the service time distribution is represented by a Coxian series of memoryless stages. We present a novel approach to the solution of such systems. Our method is based on conditional probabilities, and provides a(More)
Queueing network models of multiprogramming systems with memory constraints and multiple classes of jobs are important in representing large commercial computer systems. Typically, an exact analytical solution of such models is unavailable, and, given the size of their state space, the solution of models of this type is approached through simulation and/or(More)
A throughput-driven approach to the performance analysis of direct access storage devices (DASD's), i.e., disks, is presented for a model of a block-multiplexor channel system with multiple transfer paths. The approach relies on a step-wise analysis of shared components within the data transfer path: head of string, control unit, channel, referred to as(More)