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ARTICLE IN PRESS Optical Switching and Networking ( )

Optical Switching and Networking ( ) ­
Optimizing offset times in Optical Burst Switching networks with
variable Burst Control Packets sojourn times
A.E. Mart´inez, J. Aracil, J.E. L´opez de Vergara
Networking Research Group, Escuela Polit´ecnica Superior, Universidad Aut´onoma de Madrid. Ciudad Universitaria de Cantoblanco,
28049 Madrid, Spain
Received 19 May 2006; accepted 25 April 2007
In this paper, we consider the case of an Optical Burst Switching (OBS) network where the Switch Control Units (SCU) do not
work at the peak rate. As a consequence, some Burst Control Packets (BCPs) will have to wait in queue to be processed, and then
the BCP sojourn time will be variable. On the contrary, the optical burst does not leave the optical domain and the delay suffered
is close to the propagation delay. Hence, chances are that the BCP arrives late to a given switch and, in that case, the optical burst
will be dropped. We propose a Load-adaptive Offset Time algorithm (LOT) that takes into account the BCP variable sojourn time
for the offset time calculation. The algorithm performs on-line calculation of the Discrete Fourier Transform (DFT) of the BCPs
waiting time pdf. Our findings show that this procedure is very efficient both in terms of bandwidth usage and processing load. For
example, considering a Gaussian service time for the BCPs, it turns out than less than 45 coefficients are necessary to calculate the
offset time for a SCU utilization factor larger than 0.1.
c 2007 Elsevier B.V. All rights reserved.


Source: Rico, Javier Aracil - Departamento de Ingeniería Informática, Universidad Autonoma de Madrid


Collections: Computer Technologies and Information Sciences