nts the optical layer in different optical plans that have OXCs in common. Thus it can be devised an algorithm based on the following steps: Step 1: The first virtual network is dimensioned starting from the given layer 0 topology and assuming as traffic-only mission critical traffic. The fibers that will be equipped in this network will all be Type 3 fibers, all devoted to carry either working or protection Service Class 4 LSPs. Step 2: A second virtual network is dimensioned starting from the same layer 0 topology and assuming as traffic only high-availability LSPs. The fibers that will be equipped in this network will all be Type 2 and Type 4 fibers and are tagged SO to be possible to recognize their nature. Step 3: A third virtual network is dimensioned starting from the same layer 0 topology and assuming as traffic only standard traffic and best effort GLSPs. The fibers that will be equipped in this network will all be Type 1 and Type 2 fibers and are tagged SO to be possible to recognize their nature. This is the only step mixing two types of traffic, but it is managed easily due to the fact that best-effort traffic does not require back-up capacity. In particular, the substeps are organized as follows: A whole traffic matrix for the working traffic is created by merging standard and best-effort LSPs. The overall traffic matrix is used to dimension the virtual network for the working part. The traffic matrix relative to standard traffic only is retrieved and used to deploy protection capacity. Step 4: OXC synthesis. The OXC occupying the same topological position in each virtual network are analyzed by merging them SO to minimize their cost. The only exception is the OXC managing mission critical traffic that is not merged with other. The cost of these OXCs is on the other end recalculated doubling the cost of the interfaces to simulate 1 + 1 local interface protection. As far as the switch matrix is concerned, it is assumed to be doubled for protection in all the deployed OXCs and that this is already incl