215 research outputs found
A genetic algorithm for the design of a fuzzy controller for active queue management
Active queue management (AQM) policies are those
policies of router queue management that allow for the detection of network congestion, the notification of such occurrences to the
hosts on the network borders, and the adoption of a suitable control
policy. This paper proposes the adoption of a fuzzy proportional
integral (FPI) controller as an active queue manager for Internet
routers. The analytical design of the proposed FPI controller is
carried out in analogy with a proportional integral (PI) controller,
which recently has been proposed for AQM. A genetic algorithm is
proposed for tuning of the FPI controller parameters with respect
to optimal disturbance rejection. In the paper the FPI controller
design metodology is described and the results of the comparison
with random early detection (RED), tail drop, and PI controller
are presented
Design and performance evaluation of a state-space based AQM
Recent research has shown the link between congestion control in
communication networks and feedback control system. In this paper, the design
of an active queue management (AQM) which can be viewed as a controller, is
considered. Based on a state space representation of a linearized fluid flow
model of TCP, the AQM design is converted to a state feedback synthesis problem
for time delay systems. Finally, an example extracted from the literature and
simulations via a network simulator NS (under cross traffic conditions) support
our study
Robust control tools for traffic monitoring in TCP/AQM networks
Several studies have considered control theory tools for traffic control in
communication networks, as for example the congestion control issue in IP
(Internet Protocol) routers. In this paper, we propose to design a linear
observer for time-delay systems to address the traffic monitoring issue in
TCP/AQM (Transmission Control Protocol/Active Queue Management) networks. Due
to several propagation delays and the queueing delay, the set TCP/AQM is
modeled as a multiple delayed system of a particular form. Hence, appropriate
robust control tools as quadratic separation are adopted to construct a delay
dependent observer for TCP flows estimation. Note that, the developed mechanism
enables also the anomaly detection issue for a class of DoS (Denial of Service)
attacks. At last, simulations via the network simulator NS-2 and an emulation
experiment validate the proposed methodology
A fuzzy approach for the network congestion problem
In the recent years, the unpredictable growth of the Internet has moreover pointed out the congestion problem, one of the problems that historicallyha ve affected the network. This paper deals with the design and the evaluation of a congestion control algorithm which adopts
a FuzzyCon troller. The analogyb etween Proportional Integral (PI) regulators and Fuzzycon trollers is discussed and a method to determine the scaling factors of the Fuzzycon troller is presented. It is shown that
the Fuzzycon troller outperforms the PI under traffic conditions which are different from those related to the operating point considered in the design
AnĂĄlisis de estabilidad de controladores AQM proporcional-integral suportando flujos TCP
"Este artĂculo se centra en la estabilidad asintĂłtica de controladores AQM del tipo proporcionalâintegral suportando flujos TCP . Se proporcionan condiciones necesarias y suficientes para la estabilidad asintĂłtica de la linealizaciĂłn del sistema en lazo cerrado. Como un resultado, se obtiene el conjunto completo de controladores proporcionalâintegral que estabiliza localmente el punto de equilibrio. TambiĂ©n se aborda la robustez de los controladores a incertidumbres en los parĂĄmetros de red (nĂșmero de sesiones TCP, tiempo de viaje completo y capacidad del enlace). Se muestra que diseñando el controlador con respecto a los valores mĂĄs grandes esperados para el retardo y la capacidad del enlace, y el valor mĂĄs pequeño esperado para las cargas de TCP nos proporciona el conjunto completo de controladores robustos."This paper focuses on the asymptotic stability of proportional-integral AQM controllers supporting TCP flows. Necessary and sufficient conditions for the asymptotic stability of the closed-loop linearization are provided. As a result, the complete set of proportional-integral controllers that locally stabilizes the equilibrium point is obtained. The robustness of the controllers to uncertainties in the network parameters (number of TCP flows, round-trip time and link capacity) is also addressed. It is shown that designing the controller with respect to the largest expected values of delay and link capacity, and the smallest expected value of TCP loads leads to the complete set of robust stabilizing controllers
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