re has to be managed by the central network management. The network management has also the need of exchanging data to and from all the net- work elements; thus, it needs a transmission capacity. In general, this transmission capac- ity is different from that assigned to the control plane and, either embedded in the data network or provided with a separated network, it is called management plane. Summarizing, the architecture of a public telecommunication network spanning a geo- graphical area is composed of three superimposed plans, each plan representing a dif- ferent network component: the data plane, the control plane, and the management plane. As shown in Figure 3.16, the three plans can be represented by graphs that have the same nodes, the locations of the central offices, but potentially a different set of links, represent- ing the transmission capability available between a couple of nodes on the considered plan. Each network generally has its own control and management planes. Thus, in many present networks there are transport management and control planes to manage and con- trol the transport network and packet management and control planes to control and man- age the packet network. As we have seen in the previous chapter, this separation is a source of inefficiency push- ing carriers to work to integrate the management plane and the control plane with the target of having only one management and one control over all the network structure. Telecommunication Networks 3.2.2 Network Layering Making a design of the network starting from the base components is practically impos- sible, due to the conceptual distance between the functionalities of a single building block (like a transmitter or a filter) and the required network functions (like delivering high-def- inition television [HDTV] to selected customers or allowing World Wide Web browsing). In order to design the network, a design method capable of overcoming this separation is needed: this is the layering model. Not only the layer model is a powerf