ontrol platform. As noted in Chapter 2, the data network as it is realized at present is controlled and man- aged using different technologies. In particular, the physical layer, either SDH/SONET or OTN, has a very thin control plane, essentially used for automatic protection, and a powerful management plane, often TMN based, which centralizes almost all the management and configuration functions. On the contrary, the data network, either based on TCP/IP or on other technologies, has a powerful control plane, carrying out almost all the functions related to network configu- ration and survivability, and a slim management, generally based on SMNP. When a coordinated operation has to be carried out, it is manually implemented by accessing to the two systems in parallel. This way of managing the network is surely not optimized from the OPEX point of view, but a common control plane and management plane cannot be realized if there is no plat- form convergence. Data being the prominent type of messages to be transmitted, because also real-time services like TV and telephone can be reduced to data flows with an appropriate QoS, it is quite reasonable to converge at transport and network layers (i.e., layers four and three) on the Internet model. The IP suite has had such a huge success in the era of the Internet revolution that it is proved on very large networks and the corresponding equipment is produced in large volumes. This condition assures both solid standards and a trend of price decrease that probably will last over a long period. Moreover, the flexibility of the Internet model allows a continuous protocol suite adap- tation to new exigencies, that is, the key to introduce it into carriers' networks. Carriers have very specific requirements in terms of network monitoring and service quality and the evolution of telecommunication services in the near future is not easy to foresee; thus, the network reference architecture has to be flexible and scalable to adapt to future situations. Networks Fundamentals and Pr