ost point of view: in the first the path is not rerouted, in the second a regenerator is added along the path. As always, the less costly solution is adopted. This algorithm uses a heuristic procedure to attain a double target. With the first Dijstra routing, it tries to minimize the length of the paths, thereby minimizing the number of network elements that are needed to route and transmit them. This simple step can occa- sionally create inefficiencies, where in order to maintain short paths, a new DWDM system is opened These inefficiencies are eliminated in the second part of the algorithm when the less uti- lized DWDM systems are eliminated rerouting the path traveling through them on longer routes where equipment is already available. The efficiency of this algorithm is quite good where high-capacity LSPs are used SO that a single wavelength carries only a small number of LSPs. In this case, grooming is not very effective, and except for the inefficient cases we have mentioned, maintaining a short path route for the wavelength paths is effective in minimizing the network cost. Another element that determines the accuracy of the algorithm is the network connec- tivity. In low connectivity networks, there is little opportunity to improve the network cost by routing wavelength paths on different routes SO that a shortest path routing cor- rected for the low utilization of DWDM systems is effective in optimizing the network. The higher the connectivity, the more inaccurate the algorithm results with respect to a rigorous optimization. A final observation-the test on the transmission performances of the considered paths are done a posteriori with respect to path routing and no hypothesis is done on the system evaluation model that can be as simple or as complicated as suits the application. This regarding the working paths. At this point, either protection or restoration capacity has to be deployed. As specified at the beginning, this is done with a second design step with respect to the routing of a working capac