r SONET (using GFP in our hypoth- esis) is cheaper with respect to IP over OTN (compare with Figure 3.56). Comparing the most effective mesh and ring solutions, the presence of a threshold connectivity degree (Cm) can be noted. Above C* the mesh solution is convenient, while the multiring solution is more effective below C* This is due to the fact that the mesh Telecommunication Networks Normalized CAPEX MPLS /DWDM SONET/DWDM ring MPLS/OTN rings SONET/DWDM mesh MPLS / OTN mesh 16.25 Normalized connection degree (Cm) Normalized traffic equal to 12.5 (see Figure 4.50) FIGURE 3.59 Normalized network cost versus Cm for the different architectures at a normalized traffic level of 12.5 (average number of wavelengths per fiber link 50, network load 78%, about 10% saturated links, with 64 channels out of a maximum of 64). architecture receives better advantage from a well-connected network due to its capability to exploit all the possible routes. On the other hand, for low connectivity networks, the fact that the node equipment is less expensive for a multiring network is the most important element. This interpretation can be also confirmed by comparing the curves slope when increasing the network connection degree. In particular, the curves related to a mesh net- work decrease more rapidly increasing Cm for Cm>5. All the aforementioned results are evaluated starting from the North American net- work. It is interesting to evaluate the impact of the network topology on the results. When comparing results relative to different networks we have to take into account the different impacts due to transmission in networks covering different geographical areas. For example, focusing on the MPLS over OTN architecture, the average length of the trans- mission links in the Italian network, Figure 3.56, is only 14% of the average length of links in the U.S. network, while the German network is in between with a relative average link length of 23%. Due to this difference, transmission cost is about 70% of the overall cost for the U.S