Effect of limited fiber delay lines on QoS performance of optical burst switched WDM networks

In this paper, we address the issue of how to provide Quality of Service (QoS) with limited fiber delay lines (FDLs) at the WDM layer. We propose an offset-time-based scheme, which is less complex and more scalable than existing buffer-based schemes. The proposed scheme does not mandate any buffer at the intermediate nodes, but can take advantage of FDL-based buffers, and thus is suitable for optical networks. We discuss a couple of structures of the FDL `buffers' (which differ from the conventional queues), and evaluate their effectiveness. Specifically, the offset time required for class isolation when reserving resources such as wavelengths and FDLs is quantified. The effect of having limited FDLs on the offset-time-based scheme is measured in terms of the burst loss probability and queuing delay as a function of the offset time, the maximum delay time of FDLs, the number of FDLs, and the number of wavelengths.