are sufficient to dimension the network with optimized resources to sustain the traffic, but without any survivability strategy. In order to add survivability resources a further dimensioning step has to be done. This step is sensibly different if protection or restoration is used. We will limit ourselves to describe the algorithms that can be used in this second step, leaving to the reader the con- struction of the optimization equations. 8.4.2.2.1 Optical 1 + 1 or 1:1 Link Protection This is the simplest case; every optical link is protected through a similar link connecting the same nodes, but running on a different path (e.g., on the opposite sides of an highway or of a railway). The 1:1 protection differs from the 1 + 1 only because in the first case Telecommunication Networks low-priority traffic can be routed on the protection capacity when it is not used while in the second case the working signal is sent also on the protection path to render recovery against failure the fastest possible. In this case the transmission capacity of the links and the switching capacity of the nodes at the optical layer increments by 100%. The only attention to be paid is not to dupli- cate uselessly the OXC platforms using when possible for protection platform-free space that is present in the platforms already installed. 8.4.2.2.2 Optical 1 + 1 or 1:1 GLSP Protection At the optical layer, the GLSPs are the wavelength paths. A wavelength path starts when a set of LSPs with the same destination are aggregated by an LSR in a wavelength and sent to the collocated OXC and terminates when the wavelength is extracted by the optical layer to be delivered to the destination LSR. There is no data structure in our network model that represents directly the optical GLSPs, thus they have to be derived from the information we have. In particular, the fol- lowing criterion can be used. Every LSP is routed through the network in a known way SO that it is possible to divide the LSPs into groups SO that each group is formed by LSPs starting 