Received 8 June 2005 Copyright © 2006 John Wiley & Sons, Ltd. Accepted 10 October 2005 A novel fault management approach for DWDM optical networks W. Fawaz 1 , F. Martignon 2 , K. Chen 1 and G. Pujolle 3, * ,† 1 University of Paris 13-L2TI Lab 99, Avenue Jean-Baptiste Clement, 93430 Villetaneuse, France. 2 Department of Management and Information Technology, University of Bergamo, Italy. 3 University of Paris 6, LIP6 Laboratory, 8 rue du Capitaine Scott, 75015, Paris, France. SUMMARY Connection availability is considered as a critical metric when providing differentiated services in Wavelength- Division Multiplexing mesh networks. Indeed, one of the major concerns of optical network operators is related to improving the availability of services provided to their highest-class clients. Achieving this objective is possible through managing faults using the different classical protection schemes, namely the so-called dedicated and shared protection schemes. However, the majority of the work concerning protection schemes has considered the primary connections as equally important when contending for the use of the backup resources. As a main contribution in this paper, we therefore propose an improvement of the existing protection schemes through the introduction of relative priorities among the different primary connections contending for the access to the protection path. To evaluate numerically the benefits of the service differentiation feature introduced in our proposal, we first develop a mathematical model, based on which we derive explicit expressions for the average connection availabil- ities that result from both the classical protection schemes and the proposed priority-aware one. Through this model, we show how the availability of the highest-class clients is improved when deploying the proposed prior- ity-aware protection scheme. Finally, with the same objective in mind, we develop a simulation study, where a given set of connection demands with predefined availability requirements is provisioned using different protection strate- gies. Through this study, we show that the priority-aware protection strategy satisfies service-availability require- ments in a cost-effective manner compared with the classical protection schemes. Copyright © 2006 John Wiley & Sons, Ltd. 1. INTRODUCTION The revolutionary Wavelength-Division Multiplexing (WDM) technology increases the transmission capacity of fiber links by several orders of magnitude. In wavelength-routed WDM networks, an optical cross-connect (OXC) can switch the optical signal on a WDM channel from an input port to an output port; thus a connection (lightpath) may be established from a source node to a destination node follow- ing a path that may span multiple fiber links [1,2]. As WDM continues to evolve, fibers are witnessing a huge increase regarding their carriage capacity, which has already reached the order of terabits per second. Therefore, the failure of a network component (e.g., a fiber link, an optical cross-connect, an amplifier, a transceiver, etc.) can weigh heavily on optical carrier operators due to the consequent huge loss in data and revenue. To obtain an estimate of the different optical components’ failure characteris- tics, Table 1 presents the mean failure rates and failure repair times of various optical network compo- nents according to Bellcore (now Telecordia) [1], where Failure-In-Time (FIT) denotes the average number of failures in 10 [9] hours, Tx denotes optical transmitters, Rx denotes optical receivers, and MTTR stands for mean time to repair. INTERNATIONAL JOURNAL OF NETWORK MANAGEMENT Int. J. Network Mgmt (in press) Published online in Wiley InterScience (www.interscience.wiley.com) DOI: 10.1002/nem.601 *Correspondence to: Guy Pujolle, University of Paris 6, LIP6 Laboratory, 8 rue du Capitaine Scott, 75015 Paris, France. † E-mail: guy.pujolle@lip6.fr