DM will be composed by two addenda: 1. The first term represents transponders and is proportional to the number of wavelength (Win and will indicate the number of wavelength of the WDM on the link jn, if Win = 0 no WDM is present). The proportionality constant (unitary cost of one WDM wavelength) will be indicated with Xw. The second is proportional to the length lin and represents the infrastructure (amplifiers and SO on). The proportionality constant (cost of a unit length WDM infrastructure) will be indicated as X0. With this simple model we can try to optimize the network. In particular, we will adopt two different optimization criteria that correspond to dif- ferent balances between the cost of the transport layer and the cost of the packet layer: we will try to minimize first the cost of the nodes and then the cost of the links. In both cases we will do the realistic hypothesis that Xx < XL, that is, the port of an OXC is cheaper than a port of an LSR. 8.4.1.1 Basic Examples of Network Design In this section, we will start to introduce a few basic elements of ASON/GMPLS network design neglecting two key elements: The uncertainty on the traffic forecast and the need of designing the network SO as to allow some survivability strategy. Even if these elements are key points in a real network design, at the first moment, they would mask more fundamental issues like transparent pass-through versus grooming- based design, mesh versus hub design, and finally the importance of linear cost models. In the next section, we will reconsider the design example of this section adding design for survivability and design in uncertain traffic conditions. Section 8.4.1 is intended as a preparation to the more formal discussion about ASON/GMPLS network design that we will carry out from Sections 8.4.2 through 8.4.4. 8.4.1.1.1 Node Cost Minimization and Shortest Possible WDM Links Since we know the traffic to be routed, but we do not know the order in which the requests will arrive, we can imagine to route the GLSPs in an optimi