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Investigation of G-network with bypasses of queueing systems by positive customers at a non-stationary regime

Naumenko Victor, Kopats Dmitry, Matalytski Mikhail, Pankov Andrey

Journal of Applied Mathematics and Computational Mechanics

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2020

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Vol. 19, nr 3

85--97

EN

An open queuing network (QN) with single-line queuing systems (QS) is considered. QS are characterized by the presence of bypasses and the possibility of coming of negative customers. The network receives two independent elementary streams. The first stream is formed from the ordinary (positive) customers, while the second is composed of negative customers. Arriving of each negative customer to the system destroys exactly one positive customer in the queue, if those are contained. Negative customers do not require maintenance as the service of positive customers in the network systems is carried out in accordance with the FIFO discipline. Positive customers with a probability depending on the state of the node when they are sent to it are added to the queue, and with an additional probability, they immediately bypass it and behave in the future as served. The service in the systems is exponential, the routing of positive customers in the network is Markov, taking into account the possibility of turning the customer into a negative one after sending it to another system.

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Application of HM-networks with positive and negative heterogeneous requests for finding memory volume in information systems

Matalytski Mikhail, Zajac Pawel, Kopats Dmitry

Journal of Applied Mathematics and Computational Mechanics

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2020

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Vol. 19, nr 1

67--77

EN

To determine the memory volume of information systems (IS), it was proposed to use a stochastic model, based on the use of a queueing network with bypasses, known as an HM-network. This model includes the servicing of heterogeneous requests along with their volumes, the ability to change the volume of such requests with their passage of time and the possibility of finding computer viruses in them, and therefore servicing requests can be interrupted at some random time. The expressions were obtained for the expected total values of the volume of requests in IS nodes.

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Investigation of G-networks with restart at a non-stationary mode and their application

Matalytski Mikhail, Naumenko Victor, Kopats Dmitry

Journal of Applied Mathematics and Computational Mechanics

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2019

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Vol. 18, nr 2

41--51

EN

This article discusses the question of restarting the script, when restart is used by many users of the information network, which can be modelled as a G-network. Negative claims simulate the crash of the script and the re-sending of the request. Investigation of an open queuing network (QN) with several types of positive customers with the phase type of distribution of their service time and one type of negative customers have been carried out. Negative customers are signals whose effect is to restart one customers in a queue. A technique is proposed for finding the probability of states. It is based on the use of a modified method of successive approximations, combined with the method of a series. The successive approximations converge with time to a stationary distribution of state probabilities, the form of which is indicated in the article, and the sequence of approximations converges to the solution of the difference-differential equations (DDE) system. The uniqueness of this solution is proved. Any successive approximation is representable in the form of a convergent power series with an infinite radius of convergence, the coefficients of which satisfy recurrence relations, which is convenient for computer calculations. A model example illustrating the finding of time-dependent probabilities of network states using the proposed technique is also presented.