Elastic multi-layer resilient IP-over-Flexgrid networking: Detailed cost analysis with bandwidth-variable transponders

We introduce a mixed-integer optimization model for two-layer IP-over-Flexgrid networks, and present a cost study performed using the CPLEX package for the introduced model. The study concerns a generic German network with 12 nodes and 20 links in the optical layer, and a set of six IP traffic matrices with increasing demand volumes. The optimization assumes a hot-standby mechanism in the optical layer to make the network resilient to cable cuts. The dominant cost drivers are bandwidth-variable transponders. The numerical results reveal that due to the huge spectral capacity of a single fiber, the spectrum allocation problem simplifies significantly in practice. However, the routing problem minimizing the total cost of employed transponders becomes a challenge, but when appropriately approached and solved, can bring reductions in costs of up to 10%.