Cost functions in Optical Burst-Switched networks

Optical Burst Switching (OBS) is a new paradigm for an all-optical Internet. It combines the best features of Optical Circuit Switching (OCS) and Optical Packet Switching (OPS) while avoiding the main problems associated with those networks. Namely, it offers good granularity, but its hardware requirements are lower than those of OPS. In a backbone network, low loss ratio is of particular importance. Also, to meet varying user requirements, it should support multiple classes of service. In Optical Burst-Switched networks both these goals are closely related to the way bursts are arranged in channels. Unlike the case of circuit switching, scheduling decisions affect the loss probability of future bursts. This thesis proposes the idea of a cost function. The cost function is used to judge the quality of a burst arrangement and estimate the probability that this burst will interfere with future bursts. Two applications of the cost function are proposed. A scheduling algorithm uses the value of the cost function to optimize the alignment of the new burst with other bursts in a channel, thus minimising the loss ratio. A cost-based burst dropping algorithm, that can be used as a part of a Quality of Service scheme, drops only those bursts, for which the cost function value indicates that are most likely to cause a contention. Simulation results, performed using a custom-made OBS extension to the ns-2 simulator, show that the cost-based algorithms improve network performance. iv List of publications • Bartlomiej Klusek, John Murphy and Liam Barry, ”Cost-based burst dropping strategy in Optical Burst Switching networks”, In Proceedings of IEEE 7th International Conference on Transparent Optical Networks, July 2005. • Bartlomiej Klusek, John Murphy and Liam Barry, ”New Fiber Delay Line Usage Strategy in Optical Burst Switching Node,” in Proceedings of IASTED Networks and Communication Systems, Apr 2005. • Bartlomiej Klusek, John Murphy and Liam Barry, ”Traffic sources for Optical Burst Switching simulations,” in Proceedings of SPIE OPTO Ireland, Apr. 2005. • Bartlomiej Klusek, John Murphy and Philip Perry, ”Cost-based wavelength allocation algorithms in optical burst switching networks,” in Proceedings of Asia-Pacific Optical Communications, Nov. 2004. • Dawid Nowak and Bartlomiej Klusek, ”Analysis of Waveband Connecting Probability in Hybrid Optical Networks,” in Proceedings of 2nd IFIP-TC6 International Conference on Optical Communications and Networks, Oct. 2003. • Dawid Nowak, Bartlomiej Klusek, and Tommy Curran, ”New Method for Calculating Probability of Waveband Connection in All Optical Networks,” in Proceedings of IEI/IEE Telecommunications System Research Symposium, May 2003. • Bartlomiej Klusek, Dawid Nowak, and Tommy Curran, ”Wavelength Assignment Algorithms in an OBS Node,” in Proceedings of IEI/IEE Telecommunications System Research Symposium, May 2003. v