n. 8.4.2.4 Design in Unknown Traffic Conditions The design method we have detailed up to now relies on the fact that a reliable prediction of the traffic to be routed in a considered period of time (e.g., between two major network upgrades) is well known and that this traffic is constituted by connections that will last up to the end of the considered period. In this case, the network design does not depend on the order in which the connections are opened, since the traffic matrix is available from the beginning. This condition is called deterministic static traffic. The traffic model can be altered essentially in two ways: 1. Substituting the absolute knowledge of the traffic to be routed in the network with a partial knowledge of the traffic matrix; for example, the element of the matrix can be known only with a great approximation (like 5 <Tiji < 8) or they can be random variables with a known statistical description. In this case the design is performed in unknown traffic conditions. 2. Instead to be semipermanent, the connections are setup and tear-down several times in the considered observation period on the ground of some statistics. In this case the network is designed under dynamic traffic conditions. GMPLS sets up semipermanent connections in the transport and MPLS layers, thus dimensioning in conditions of dynamic traffic does not occurs in the bottom layers of the network. On the contrary, if the dimensioning was performed for a TCP/IP network, since TCP set-up and tear down continuously connections design in dynamic conditions would be needed. On the other hand, the consolidation of competition among carriers and in general the uncertainty on the penetration of new services renders the knowledge of the traffic matrix less and less precise SO that dimensioning is often performed in conditions of unknown traffic. In order to use a dimensioning algorithm in these conditions, it is needed to set up a method to manage the unknown traffic condition. The problem is widely studied in litera- ture and in gen