Incremental capacity dimensioning for reliable IP-over-WDM networks

In order to construct a reliable IP over WDM network, backup paths as well as primary paths should be embedded within a wavelength-routed topology (or logical topology). However, many conventional approaches assume that the traffic demand is known a priori. In this paper, we propose a new approach, called an incremental capacity dimensioning approach, to build the logical topology. Our incremental approach consists of three steps for designing the logical topology: an initial phase, an incremental phase, and a readjustment phase. By our approach, the logical topology can be adjusted according to the incrementally changing traffic demand. During the incremental phase, the backup lightpaths are reconfigured when the new primary path is set up since the backup lightpaths do not affect the carried traffic on the primary paths. Our proposed algorithm, called MRB (Minimum Reconfiguring for Backup lightpath), assigns the wavelength route in such a way that the number of backup lightpaths to be reconfigured is minimized. Then, the backup lightpaths are actually reconfigured. For this purpose, we also formulate an optimality problem for reconfiguring the backup lightpaths. Our results show the total traffic volume which the IP over WDM network can accommodate is improved by using our MRB algorithm.