 that some activities cannot start again if they are still ongoing. Once the models are set up, we can evaluate the overall OPEX expenditure of the carrier. This is estimated by adding all the costs of parallel recurring or continuous activities. As far as the spot activities are concerned, their costs are weighted with the probability of the trigger, SO to take into account the fact that they are not continuous. Here we will not report the real activity graphs of the most complex activities, and much more details are reported in Refs. [28,29]. We will limit our self to list the main activities and the impact of the introduction of ASON/GMPLS on them. The main activities are all periodical or continuous, thus we will not repeat this every time. Cost of failure free network operation: This is the base cost to take the network opera- tional in a failure-free situation: it includes the cost of electrical power, building leasing for central offices, fiber leasing if it is the case, permissions for traversing private properties or to bring cables in private buildings, taxes on the ownership of the infrastructure and SO on. This cost is heavily impacted by ASON/GMPLS due to the change of several equipments and to the substitution of preprovisioned protection with restoration in several areas of the network with a consequent reduction of the number of network equipments. Routine operations: This is the cost related to all actions aimed to maintain the network in an efficient working status, maintaining the ability to face a possible failure. The main actions performed here aim at monitoring the network and its services. Therefore, the actions involved include the following: Periodic verification of the equipment performances and services quality ver- sus existing SLAs. Management of the spare parts warehouses and activity to assure spare parts availability when a failure occurs. Software management in terms of patches and new releases installation and bugs tracking. Alarms management with all the activities aimed to fai