Wyniki wyszukiwania - BazTech

1

Link-level, congestion avoiding flow control solution for IP networks

Karbowańczyk M.

Przegląd Elektrotechniczny

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2011

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R. 87, nr 12a

225-230

EN

In this paper a complete flow control solution for IP networks is presented. The mechanism consists of feedback loop and quantity-based control algorithm that utilises the Smith predictor and dead-beat control. In contrast to several proposals where flow-level control using bottleneck node approach is performed, in our solution the feedback loop is established between two neighbour nodes, what is called link-level control. The results of experiments performed in real IP network show that it is possible to completely avoid node congestion and increase throughput utilisation in the network area where the proposed solution is applied.

PL

W artykule przedstawiono kompletny mechanizm sterowania przepływem danych w sieciach IP. Mechanizm ten składa się z pętli zwrotnej oraz algorytmu sterowania wykorzystującego predyktor Smitha i regulator typu dead-beat.Zastosowano sterowanie na poziomie łącz, w którym pętla zwrotna jest zestawiona pomiędzy sąsiednimi węzłami sieci. Mechanizm został poddany weryfikacji eksperymentalnej w rzeczywistej sieci IP, zaś uzyskane wyniki potwierdziły jego skuteczność w zakresie eliminowania przeciążeń sieci i poprawy efektywności wykorzystania jej zasobów.

2

Packet Switching Networks Traffic Prediction Based on Radial Basis Function Neural Network

Zaleski A., Kacprzak T.

Journal of Applied Computer Science

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2010

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Vol. 18, nr 2

91-101

EN

New multimedia applications require Quality of Service support, which is still not successfully implemented in current packet-switched networks implementations. This paper presents a concept of neural network predictor, suitable for prediction of short-term values of traffic volume generated by end user. The architecture is Radial Basis Function neural network, optimized with respect to a number of neurons. Testing mode of the neural network is very fast, what enables application of this tool in nodes of telecommunication network. This would help to warn a network management system on early symptoms of congestion expected in the near future and avoid the network overload.

3

Design of the state predictive model following control system with time-delay

Wang D., Wu S., Okubo S.

International Journal of Applied Mathematics and Computer Science

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2009

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Vol. 19, no 2

247-254

EN

Time-delay systems exist in many engineering fields such as transportation systems, communication systems, process engineering and, more recently, networked control systems. It usually results in unsatisfactory performance and is frequently a source of instability, so the control of time-delay systems is practically important. In this paper, a design of the state predictive model following control system (PMFCS) with time-delay is discussed. The bounded property of the internal states for the control is given, and the utility of this control design is guaranteed. Finally, examples are given to illustrate the effectiveness of the proposed method, and state predictive control techniques are applied to congestion control synthesis problems for a TCP/AQM network.

4

A buffer thresholds policy in linked in series servers with blocking

Oniszczuk W.

Elektronika : konstrukcje, technologie, zastosowania

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2009

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Vol. 50, nr 11

51-54

EN

The use of buffer thresholds, blocking and adequate service strategies are well-known techniques for computer networks traffic congestion control. This motivates the study of series queues with blocking, feedback (service under Head of Line (HoL) priority discipline) and finite capacity buffers with thresholds. In this paper, the external traffic is modelled using the Poisson process and the service times have been modelled using the exponential distribution. We consider a three-station network with two finite buffers, for which a set of thresholds (tm1 and tm2) is defined. Using an open Markovian queuing schema with blocking, priority feedback service and thresholds, a closed form cost-effective analytical solution is obtained. Based on numerical experiments and collected results we conclude that the proposed model with blocking, feedback and thresholds can provide accurate performance estimates of linked in series servers.

PL

Zastosowania progów w buforach, koncepcja blokad i odpowiednia strategia obsługi, to szeroko używane sposoby przeciwdziałania przeciążeniom w systemach komputerowych. Często więc, obiektami badań są kolejkowe systemy obsługi z blokadami, recyklingiem (obsługa priorytetowa) i ograniczonymi buforami z dynamicznymi progami. W niniejszej pracy założono, że zewnętrzny strumień zadań jest strumieniem Poissona, a losowe czasy obsługi mają rozkład wykładniczy. Badana sieć składa się z trzech węzłów, a w buforach mamy progi o rozmiarach tm1 i tm2. Na bazie formalizmów łańcuchów Markowa, powstały efektywne modele analityczne takich systemów obsługi, a seria eksperymentów numerycznych pokazała, że koncepcja blokad, recyklingu z priorytetami, oraz z dynamicznymi progami dobrze opisuje procesy obsługi w takich systemach.

5

New challenges in dynamical systems: the networked case

Bauer P. H.

International Journal of Applied Mathematics and Computer Science

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2008

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Vol. 18, no 3

271-277

EN

This paper describes new technical challenges that arise from networking dynamical systems. In particular, the paper takes a look at the underlying phenomena and the resulting modeling problems that arise in such systems. Special emphasis is placed on the problem of synchronization, since this problem has not received as much attention in the literature as the phenomena of packet drop, delays, etc. The paper then discusses challenges arising in prominent areas such as congestion control, sensor networks, as well as vehicle networks and swarms.

6

Dyskretne algorytmy sterowania szybkością nadawania danych w połączeniowych sieciach teleinformatycznych

Molik T., Bartoszewicz A.

Kwartalnik Elektroniki i Telekomunikacji

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2006

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Vol. 52, z. 4

563-589

PL

W artykule zaprezentowano dwa nowe dyskretne algorytmy sterowania szybkością nadawania danych w połączeniowych sieciach teleinformatycznych. Proponowane rozwiązania wykorzystują predyktor Smitha oraz dyskretny regulator proporcjonalny. Jeden z algorytmów uwzględnia także informację o stanie sieci dostarczaną przez sprzężenie bezpośrednie od dostępnego pasma, co przyczynia się do zmniejszenia wahań czasu opóźnienia związanego z kolejkowaniem danych w węźle wąskiego gardła. Wykazano, że przy spełnieniu odpowiednich warunków przedstawione algorytmy pozwalają całkowicie wyeliminować przeciążenia sieci oraz zapewniają pełne wykorzystanie łącza. Algorytmy zachowują swoje właściwości zarówno w stanie ustalonym sieci, jak i wtedy gdy liczba nadajników oraz dostępne pasmo mogą ulegać zmianie.

EN

The paper presents two new discrete time flow control algorithms for connection oriented communication networks. The algorithms effectively combine the Smith predictor with a discrete time, proportional controller. One of the strategies proposed in the paper uses also the feed-forward compensation of the time varying available bandwidth. This helps reduce transport delay and its variance, consequently ensuring improved quality of service (QoS). It has been proved that the algorithms eliminate the risk of the bottleneck buffer overflow and assure full bandwidth utilisation. The algorithms proposed in the paper maintain these desirable properties not only in the steady state, but also when the number of data sources and the available bandwidth may change during the network operation. The algorithms can support an arbitrary bandwidth allocation, which is their important advantage when compared with other strategies proposed in the past. The favourable properties of the proposed control algorithms are strictly proved and verified by means of a simulation example.

7

Feed-Forward Bandwidth Compensation in Connection-Oriented Networks with Rate-Dependent Sampling

Ignaciuk P., Bartoszewicz A.

Journal of Applied Computer Science

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2006

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Vol. 14, nr 1

79-95

EN

In this paper, congestion control in a connection-oriented network supporting multiple data flows is considered. In the examined network the feedback information is received by each source once every M data packets sent by this source round trip time earlier. Since the rate is modified only, when this information becomes available, the transfer speed changes at irregularly spaced time instants. A new, nonlinear controller effectively combining the Smith predictor with the feed-forward compensation is proposed. Conditions for data loss elimination and full bottleneck link bandwidth utilization are formulated and strictly proved with explicit consideration of irregularities in the feedback information availability. Furthermore, due to the employed feed-forward compensation, the variation of the data transfer delay is reduced, which ensures favorable Quality of Service in the network.