2, and the number of wavelength is 4, one for each link of the network (it is always assumed w sufficiently large). The formal expression providing the cost of the network in this third case, indicating with H the node number of the hub, is (8.3) Telecommunication Networks Cost relative to the first design method V=Xx1XL Design 2, V = 8 v=0.5 FIGURE 8.21 Design 3, V = 8 Dimensioning results: cost for second and third design methods normalized to the cost of the first method for different values of the cost parameters. z=X01XL Also in this case, neglecting the integer part to return at the greater integer after achieving the noninteger result, we arrive at a linear expression of the design variables; moreover, as also expected, the hub has a completely particular role in Equation 8.3. 8.4.1.1.4 Comparison between the Design Methods Since the design methods we have introduced aim at different kinds of network optimi- zation they have to be compared when the cost variables of the network changes. Just to have a feeling of what happens, let us put Xx = V XL and X0 = 3Xw = Z XL SO as to have only two cost parameters: Z and V. Increasing z, the cost of the WDM is more and more preva- lent, while the contrary happens decreasing Z. On the other hand, the ratio between the cost of the node at layer 1 and at layer 2 is regulated by V. Figure 8.21 reports the network cost relative to the base cost obtained with the first method when the second or the third methods are used. As intuitive, increasing z, the cost of the WDM links is more important and the design with optimized WDM links becomes preferable. This trend is almost independent of V, since the number of ports of LSRs and OXCs have almost the same trend with Z. With high values of v, an LSR port costs much more than an OXC port, and the hub design that reduces the OXC dimensions at the expense of a double passage of each GLSP through an LSR is not convenient. On the contrary, for low values of V sparing in OXC ports is meaningful, since one OXC port costs much more t