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 avoidmg the mam 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 burst 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 functio n 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 droppmg 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 performanc

Cost-based burst dropping strategy in optical burst switching networks

Optical burst switching (OBS) is a new paradigm for future all-optical networks. Intentional burst dropping is one of techniques used to achieve desired quality of service. In this paper we note that some bursts are more likely to cause contention. We propose a cost function that can be used to predict the likelihood that a given burst will interfere with other traffic, then we explain how, by using this information a new burst dropping strategy can be designed. We compare our method with a random burst dropping technique and show that the cost-based approach offers a significant performance improvement

Cost-Based Burst Dropping Strategy in Optical Burst Switching Networks

ABSTRACT Optical Burst Switching (OBS) is a new paradigm for future all-optical networks. Intentional burst dropping is one of techniques used to achieve desired quality of service. In this paper we note that some bursts are more likely to cause contention. We propose a cost function that can be used to predict the likelihood that a given burst will interfere with other traffic, then we explain how, by using this information a new burst dropping strategy can be designed. We compare our method with a random burst dropping technique and show that the cost-based approach offers a significant performance improvement

New Fiber Delay Line Usage Strategy In Optical Burst

Optical Burst Switching (OBS) is a new paradigm for future all-optical networks. In an OBS node, a Fiber Delay Line may be used to delay a burst, effectively increasing its offset time. Traditionally, FDLs were used in contention resolution, i.e. a burst was only buffered if it would otherwise been dropped. We propose a different approach, where delay lines are used also to better arrange bursts in time. In our strategy both outgoing channels and FDL channels are assigned a price, according to their suitability for a particular burst. When a control packet arrives at a core node, all the possible ways of handling the corresponding burst are found (the outgoing channel, with or without a FDL), and the one with a lowest total price is chosen. This makes it possible to use most FDL channels for the majority of the time, reducing the probability of future contention. We present simulation results, showing how node performance depends on the size of a FDL bank, using either Last Available Unused Channel with Void Filling (LAUC-VF) and the traditional FDL usage strategy or our algorithm