w network equipment have been analyzed. In practical network planning, however, there is another key issue to take into account. The network evolution from one technology to another is a process lasting several years, during which the network is in an hybrid situation where new and old equipment have to coexist with- out a disruption of services. Moreover, even when the transition to the new technology is completely carried out, old technology machines that are still working properly are not eliminated from the network but are still used up to the end of their lifetime, in the worst case, moving them away from the most critical part of the network to be deployed where the situation is less critical. This fact has a consequence: the survival of isles where the TDM technology is still used for a time much longer than the time strictly needed to deploy the packet technology, with the need of implementing in the new machines (either the packet switches/routers or the WDM transmission systems) interfaces that are suitable to integrate them with the TDM equipment. Telecommunication Networks 2.2.3 Requirements for Next Generation Network Control Plane In the old network, imagining that a new path was needed to connect new ATM interfaces installed in the data network, a long procedure was needed: The data network had to be preconfigured locking the resources needed for the new capacity. The control plane of the transport network had to be manually programmed in order to provision new paths providing the required new transport capacity. When the new paths were provisioned and tested, the transport resources were assigned to the newly created paths that can start working. The presence of the required paths is communicated to the control plane of the packet network that is manually induced to set up the wanted capacity. Generally, since the departments managing the transport network and the packet one were different, the control SWs were located in different buildings and communications between them were carried out by phon