ork in terms of nodes topology: the topology in which the physical net- work nodes are represented by the nodes of the topology graph. Telecommunication Networks We will imagine that all the fiber cables are owned by the carrier that is designing the network SO that the bare use of a free fiber is cost free and that a fiber is always available on each route where a cable is present. The topology will be meshed at every network layer. The layering is also given: in our examples, an MPLS layer is imagined to be superimposed on the optical layer. In all the nodes where an OXC is deployed at layer one, an LSR is deployed at layer 2. Equipment type is already selected when doing network dimensioning at every network layer; thus, all the cost parameters are given. Once these hypotheses are set, the cost of the model for the network elements can be set on the line of what is done in Chapter 8. Thus, the dimensioning can be divided into two steps: dimensioning of working capac- ity and dimensioning of protection/restoration capacity. All the constraints of Chapter 8 still hold: Traffic continuity across the nodes at every layer and bidirectional GLSP Traffic continuity across the layer boundaries Number of wavelength deployed on each link sufficient to support the LSP travel- ing through the link Contiguity of the link constituting an LSP path at every layer Contiguity of the nodes at the extremes of each LSP hop In the case of a transparent network, however, these constraints are not enough. As a mat- ter of fact, whenever a WC is not present, the physical continuity of a wavelength has to be assured. Moreover, the transmission performances of the transparent paths that are dimensioned have to be verified, since it is not at all guaranteed by a dimensioning algorithm minimiz- ing the cost of the network. 10.3.4.2 Problem of Wavelength Routing and the Use of Wavelength Converters As far as the first problem is concerned, the more rigorous way to face it is to divide the matrix [1]R] (see Chapter 8) into wavelength planes