Saving CAPEX by extending flexgrid-based core optical networks toward the edges [invited]

National IP/multiprotocol label switching (MPLS) networks have been designed using a multilayer approach to take advantage of the optical layer's longer reach. In that approach, the IP/MPLS layer performs routing and flow aggregation, whereas the optical layer, based on wavelength division multiplexing technology, transports those aggregated flows into optical connections. However, the flexgrid technology, featuring a finer granularity, also allows the performance of grooming at the optical layer, and hence, the aggregation level of the incoming flows can be reduced. Taking advantage of that fact, in this paper we propose a new network architecture consisting of a number of IP/MPLS areas performing routing and aggregating flows to the desired level and a flexgrid-based core network connecting the areas among them. A two-step procedure to design the whole network is presented where locations are first partitioned into a set of areas, and then each area network and the flexgrid core is designed separately. Mixed-integer linear programming models are developed for the resulting optimization problems. Solving these models, however, becomes impractical for real-sized scenarios so evolutionary heuristics based on the biased random-key genetic algorithm framework are also proposed. Extending the core toward the edges results in significant savings in both the core and IP/MPLS networks.