In this paper we study different options for the survivability implementationin MPLS over Optical Transport Networks (OTN) in terms of network resourceusage and configuration cost. We investigate two approaches to thesurvivability deployment: single layer and multilayer survivability and presentvarious methods for spare capacity allocation (SCA) to reroute disruptedtraffic. The comparative analysis shows the influence of the offered trafficgranularity and the physical network structure on the survivability cost: forhigh bandwidth LSPs, close to the optical channel capacity, the multilayersurvivability outperforms the single layer one, whereas for low bandwidth LSPsthe single layer survivability is more cost-efficient. On the other hand,sparse networks of low connectivity parameter use more wavelengths for opticalpath routing and increase the configuration cost, as compared with densenetworks. We demonstrate that by mapping efficiently the spare capacity of theMPLS layer onto the resources of the optical layer one can achieve up to 22%savings in the total configuration cost and up to 37% in the optical layercost. Further savings (up to 9 %) in the wavelength use can be obtained withthe integrated approach to network configuration over the sequential one,however, at the increase in the optimization problem complexity. These resultsare based on a cost model with different cost variations, and were obtained fornetworks targeted to a nationwide coverage.
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