Trading Power Savings for Blocking Probabilityin Dynamically Provisioned WDM Networks

In those networking scenarios (e.g., the stationary/mobile wireless paradigm) where limited energy storagecapabilities is a limiting factor, power efficiency has been studied extensively for a long time. In the last fewyears, the steadily growing power consumption figures of ICT [1][2] along with a recent public awareness of thepossible environmental effects, broadened the focus of the research efforts towards more power conscioussolutions also for wired networks. One promising solution going in this direction is represented by transparentwavelength division multiplexing (WDM) networks, where all-optical circuits (or lightpaths) carry the networktraffic from the source to the destination node in the optical domain, i.e. without any optical-to-electrical(O-E-O) conversion. To further improve network power efficiency, several approaches have been proposed inthe literature attempting to reduce the power consumption in transparent WDM networks [3][4]. Among them,power aware (PA) routing and wavelength assignment (RWA) algorithms are receiving a lot of attention. Onepossible solution for the PA-RWA problem is to limit the number of devices in the network that need to bepowered-on to support the lightpath requests [5]. These methods, however, have an adverse impact on the lengthof the provisioned lightpaths. In order to efficiently use as much powered-on network resources as possible, thepath length is, on average, longer than the one found with traditional (and less power efficient) shortest pathsolutions. This is in contradiction with the goal of classical RWA algorithms that tend to minimize the resourceusage (i.e., wavelengths and fibers) within the network, in order to minimize the blocking probability. Whenavailability of network resources becomes something that cannot be overlooked, a trade off needs to be assessedbetween power savings and blocking probability.In this talk, a non-conventional solution to the PA-RWA problem is presented. It is based on the intuitionthat, in some cases, relaxing the power minimization constraint can have beneficial effects on the overallnetwork performance, i.e., it can contribute to the reduction of resource fragmentation in the network and, in thisway, lower the blocking probability. The proposed algorithm leverages on a cost function that considers both thepower status of network elements (in this particular case the in-line optical amplifiers on fiber links only) and theinformation about wavelength usage. The algorithm has been tested using a Pan-European core network (i.e.,COST 239). Performance results confirm the presence of a trade-off between energy saving and blockingprobability. They also suggest that a “binary” approach using only the powered-on/powered-off informationmight not always be the best choice.© 2010 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works. QC 20120202