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reference.AbstractThe increasing usage of the Internet around the world leads to a massive growth in traffic volumeand dynamics to be handled by the network backbones. To cope with this development, severalhigh dynamic solutions like optical burst switching (OBS) and optical packet switching (OPS) havebeen investigated during the last few years. They all can cover the high dynamics of Internettraffic, but there is no direct migration path from today’s static SDH/SONET-based WDM networkstowards IP-over-OBS/OPS as these technologies require a completely new infrastructure (nodesetc.) and control systems. This argument is even stronger in presence of the current marketdownturn.One feasible solution to cover the dynamics of IP traffic is the concept of enhanced automaticallyswitched SDH/SONET-WDM
multilayer networks. The major reason for this approach is the factthat dynamics can be covered and at the same time an evolution path for today’s SDH-centricnetworks exists.SDH/SONET-WDM multilayer networks provide dynamics on both layers and consist of multilayer nodes with cross connects on the SDH/SONET layer as well as on the WDM layer (Fig. 1).
Dimensioning of multilayer networks for dynamic traffic requests is a key problem that has to besolved.The objective of the dimensioning process is to minimize the network infrastructure cost and theblocking probability for arriving connections at the same time. The performance of multilayernetworks is significantly influenced by routing strategies and assignment of different lowerbandwidth SDH connections to wavelengths, often referred to as grooming. In general, assigninggiven connection demands to dedicated resources dimensions static networks. In the case ofWDM networks, this process is referred to as the routing and wavelength assignment problem(RWA). Several solutions to the static RWA problem have been investigated which minimize thetotal number of wavelength hops in the network.However, in dynamic networks connection requests arrive and terminate statistically. Meanvalues of utilized end-to-end bandwidth are given in traffic matrices and distributions are used forthe inter-arrival and holding time of connections. Although a static dimensioning based on meanvalues of connection requests could be used for dynamic networks this dimensioning may not beappropriate. The law of the economy of scales states that a small channel trunk requires moreresources for reaching the same blocking probability than a large trunk under the same load perchannel. Also, the adoption of dimensioning methods used in other dynamic multilayer networks(e. g. IP-over-ATM) is no valid solution. These networks are usually operated and dimensioned ina single layer mode without regarding the dynamics of underlying layers. Therefore, newdimensioning schemes are necessary.