orking path as if wavelength conversion was present everywhere. The obtained path routes are divided into the minimum number of sets of routes (named layers), such that in each layer, as many links as possible are occupied, and no wavelength path share links with wavelength paths of the same layer. This operation is carried out by a trial and error procedure, creating sets and ana- lyzing them to find the better set from the considered point of view. The trial and error procedure can be simplified by observing that Partitions that put in the same set a lot of wavelength path crossing the same links can generally be discarded immediately, since each wavelength path in the same set will have the same wavelengths, thereby forcing the design to open several DWDM systems on the same link. Next Generation Networking: Enabling Technologies, Architectures, and Performances Partitions that comprise sets with a small number of paths and sets with a large number are generally less efficient. Let us call B the average number of layer. In doing so, take into account that if regenerators are allowed, they can change the wavelength of the path they regenerate. Assign a layer number randomly to each layer SO that each number appears once. Assign a wavelength cyclically to each layer according to the layer number. Evaluate the system cost according to the wavelength assignment performed in Step 4. Iterate from Steps 3-5 a certain number of times, finding the layer assignment that gives the minimum network cost A similar algorithm is used for the backup capacity. We will list only the version for restoration: Determine restoration capacity as if WC where available everywhere. From the restoration table, assign to each restoration path, the same wavelength of the corresponding working path. When capacity sharing among paths with different wavelengths occurs, either introduce new wavelengths as needed if regenerators are not allowed, or compare the solution with the new wavelength with the solution with one regenerator that changes 