In this paper, we propose a new wavelength-reservation-based dynamic routing and wavelength assignment algorithm (RWA) to improve the fairness of previous RWA algorithms in wavelength-routed WDM networks. In the algorithm, RWA solutions available from static optimal virtual topology design are used to determine a set of wavelengths to be reserved on corresponding routes for each node pair. Based on the wavelength reservation, a set of dynamic wavelength allocation policies is proposed to use the reserved wavelengths efficiently by allowing the reserved wavelengths to be used by others. Simulation results based on NSFNET topology show that a modified RWA algorithm based on wavelength reservation can improve the fairness of the original RWA algorithm and can reduce the overall blocking probability when traffic load is low.
This paper studies the virtual topology design of wavelength-routed WDM networks. The focus is on the virtual topology design problem taking into account the quality of service (QoS) requirements of different user applications. To provide diverse QoS levels to meet different QoS requirements, we first propose a QoS model for WDM networks, in which we define four types of optical connections, each providing a diverse QoS level in terms of the transmission bandwidth and end-to-end delay. Correspondingly, we classify the network traffic into four categories with different QoS requirements for using the four types of connections. Based on this QoS model, we then formulate the virtual topology design problem as a linear programming problem with an objective to maximize the network throughput, and give an exact formulation of the problem.