OADM-like functionalities. This new physical layer will be able to interact in a more intelligent way with the upper IP/MPLS layer, thanks to its processing functionalities allowing effective interlayer coordination for a more optimized generalized multiprotocol label switching (GMPLS) network architecture. Naturally, the key technology to be developed to target this kind of network is mono- lithical integration of electronics and optics in order to reduce the cost of the equipment. 10.1.2 Optical Transparent Network If no revolution happens in the field of integration between electronics and optics, optical equipment will remain cheaper than the corresponding electronic equipment, due to its ability to deal simultaneously with a set of very-high-speed signals. This is why when the WDM revolution invested the telecommunication networks, there was a diffused agreement on the fact that electronics was destined to disappear from the physical layer, substituted by an "all-optical" transparent network. Even if a huge amount of research and industrial development has been done in this direction, the idea of a completely analog physical layer faces important problems when the implementation of control plane and management functions is considered. Moreover in a network whose node regenerates the signal, the network design and opti- mization are decoupled by the design of the transmission systems (see Chapters 6 and 8). In a transparent network, wavelength routing has to be performed taking into account transmission impairments SO as to avoid routes that are not feasible from the transmission point of view. These difficulties, besides the great progresses of electronics, have quite attenuated the enthusiasm for the optical transparent solution. Nevertheless, this is still one of the pos- sible network evolutions. 10.1.3 Optical Packet Network The reason why optics seems SO suitable to scale up the capacity of the network is its ability to deal with very-high-speed signals without the need of dividing them into lower speed