zed way and then to use the constrained routing to reproduce such optimized configuration whatever be the order of the requests. In order to minimize the node cost and, in situations in which the node cost does not change, to have the shortest possible WDM links, we will proceed as follows: GLSPs and OXC have to be installed in every node. WDM links are installed in links l23, l34, SO to form a sort of ring. Link between nodes 2 and 4 is not equipped. The GLSP between nodes 2 and 3 is routed through the direct route that is also the shortest route of the graph. The GLSPs from nodes 1 to 3 are routed through node 4 in order to have a WDM link of length 6 instead of 7 that is the length of the connection 1 2 The GLSPs from 3 to 4 are also routed through the direct route. Telecommunication Networks The LSR ports are used only to generate and terminate local GLSPs and the transport completely performed at the WDM layer. When an GLSP has to pass-through a node, it is switched by the OXC. This kind of design produces the following numbers: The number of ports of LSRs is 2T, where T is the overall number of routed GLSPs. This is the minimum number of LSR ports: two for each GLSP in the net- work. The property that the lower bound of the number of higher layer GLSRs ports is equal to twice the sum of the elements of the traffic matrix holds, of course, in general and it is a useful way for a fast evaluation of the order of magnitude of the number of ports. The number of ports of OXCs is where thik is the number of GLSPs from node to node k and it has been assumed, as reasonable, w >> Max (tn.k). In the aforementioned equation [x] is the smallest inte- ger greater than x and Thik is the so-called crossing factor, which is the number of intermediate nodes the GLSPs from node h to node k traverse. Naturally this number can be defined only if all the GLSPs with the same end nodes are routed through the same route, and in complex networks, this is not obvious. However, in our simple case, this definition allows us to obtain a