sign of an optical transparent network on the WCs when needed Italian topology; systems with 128 and 64 wavelengths are considered besides the three types of OXCs described in the Traffic (capacity of routed paths, Tbit/s) previous section 10.3.2. Next Generation Networking: Enabling Technologies, Architectures, and Performances OXC platform OXC WCs OXC space diversity switch fabric Comparing the cases with 128 and 64 wavelengths, the intuitive result is that the more wavelength a system allocates in the same bandwidth (in our case all channels are in the C band), the lower the cost. As a matter of fact, all cost factors are the same, but the DWDM platform is almost cut to half. More complex is the situation that creates the application of different WC placing strategies. Starting with the case without WCs, the only way to avoid a traffic request refusal is to increase the dimension of the switches and, consequently, the number of DWDM systems. As a matter of fact, if we compare the overall number of ports of the OXCs of all the net- works in analogous conditions, we find that using PWP OXCs there are more ports than using PWC OXCs. Thus, in the PWP case, the average OXC machine, as well as the network, is more expensive. Comparing the PWC and the LWC case, the algorithm used is able to design the network with the LWC OXCs in a way that the number of OXC ports is the same at every node. In this condition, the DWDM infrastructure is the same in the two cases, and the only relevant cost difference does exist regarding the OXC switch fabric. In the PWC case, if the fabric is assumed to be a cross bar matrix, we have (NW)2 cross- points and NW WCs. In the typical LWC case, we have W(N + 1)2 cross points, and gener- ally, W WCs. If the cost of a WC is K times the cost of a cross point (where K is on the order of 900), the ratio p between the cost of the network using PWC and LWC is (10.28) W(N+1)²+KWN-K/N This very simple analysis also shows that by increasing N, the advantage of the LWC over the PWC is about W, which