er OTN GFP is a powerful tool for integrating packet switched networks over a SONET transport; it is SO attractive for a carrier to rely on well-known and assessed manageability and reli- ability of SONET network that several vendors, mainly in North America, are designing a new generation SONET as a tool for network evolution. However, relying upon SONET or SDH equipment does not allow reducing the num- ber of equipment that it is necessary to deploy in a core network node. Increasing the number of wavelength in DWDM systems, the number of SONET/SDH network elements increases with two detrimental effects. First of all, the CAPEX needed to expand the network increases almost linearly with the capacity due to the fact that if SONET machines process a group of wavelengths, for every new group that is activated a new SONET/SDH network element has to be added. Second, the SONET/SDH network becomes rapidly composed of a large number of superimposed and potentially independent networks, one for each layer composed by a group of wavelengths (e.g., the wavelength entering the same set of DXCs). This is not the best way to efficiently exploit the transmission capacity, since grooming among different wavelengths is not possible and free capacity on one wavelength plane cannot be used to relieve congestion on another plane. This last problem could be solved by a network design based on big DXCs and a mesh topology instead of ADMs and a ring topology, SO that the DXC can terminate every wave- length of the WDM systems arriving at its node. In this case, the needed DXCs would have huge dimensions and the related cost would be huge too. As an example, to interface five in and five out DWDM systems at 10 Gbit/s using 64 wavelengths each, a DXC with a Networks Fundamentals and Present Architectures bidirectional capacity of 3.2 Tbit/s would be needed. Since a DXC performs SDH/SONET path layer operations, it should decompose the incoming signals into the client VCs (or VTs) in order to perform grooming optimization at the path la