l (E-to-W) Out port label (E-to-W) In port label (E-to-W) Out port label (E-to-W) FIGURE 8.15 Generalized Label Assignment for a bidirectional GLSP. Convergent Network Management and Control Plane GLSPs OSPF-TE routing A B -> C E-> D A-> D-> C-> B Optimized routing A-> D-> C-> B A-> D-> C B-> E B-> E-> D A-> B FIGURE 8.16 An example of sub-optimum routing performed with OSPF-TE. Each link between a couple of GLSR is assumed to have enough capacity to support only two GLSPs. Such an example is provided in Figure 8.16. Here a network of five nodes with an incom- plete mesh connection is represented. For simplicity let us image that each link is physi- cally realized with a WDM system with two wavelengths and that all the wavelengths have the same capacity, which we assume equal to 1. Let us also imagine to tag every link with a weight that is the "cost" of using a wave- length along that link. We could also think that the weight is the link length and that it is assumed as a cost due to the fact that WDM systems have a cost roughly proportional to length. Such GLSPs, each of which for simplicity is imaging to have unitary capacity, SO that it completely uses a single wavelength, correspond to traffic requests arriving at the network control plane one after the other SO that they are routed in successive times and when one of them is routed the network control plane does not know what set of traffic requests will arrive in the future. In this dynamic situation, typical of GMPLS networks, the OSPF-TE protocol produces the routing that is listed in the first routing table in Figure 8.16. Naturally, also IS-IS would have produced the same routing due to the use of the same routing algorithm and to the fact that this simple network is a single routing area. The overall cost of the routing is obtained by adding together all the costs of the used wavelengths and it is reported in the figure as 335. However, it is not difficult to see that at least one alternative routing exists having a lesser cost, reported as 325 in Fig