Optical layer survivability for single and multiple service classes

This paper considers capacity provisioning for service and restoration in a WDM optical network which provides lightpaths to higher layer networks. An optical network will likely serve several client networks with different protection requirements from the optical layer. In this paper, a framework is developed for jointly assigning wavelengths to service and restoration paths for all failures, for traffic patterns with single or multiple classes of protection. For various restoration methods, the problem is reduced to a vertex coloring problem in a graph. We present routing and wavelength assignment algorithms for service and restoration with varying capacity/restoration time tradeoffs, and evaluate their performance through simulations. We consider three different kinds of traffic patterns in terms of protection requirement: 100% protected traffic, mixed protected/unprotected traffic, and mixed protected/low-priority traffic. We quantify the capacity cost of protection in mixed traffic patterns as a function of the proportion ρ of the protected traffic in the mix, and identify the range of ρ where protection can be provided at low capacity penalties. This is important for assessing the economical feasibility of providing protection to a class of connections at the expense of reducing the amount of traffic that could be served without protection guarantees.