In this paper we study different options for the survivability implementationin MPLS over Optical Transport Networks in terms of network resource usage andconfiguration cost. We investigate two approaches to the survivabilitydeployment: single layer and multilayer survivability and present variousmethods for spare capacity allocation (SCA) to reroute disrupted traffic. Thecomparative analysis shows the influence of the traffic granularity on thesurvivability cost: for high bandwidth LSPs, close to the optical channelcapacity, the multilayer survivability outperforms the single layer one,whereas for low bandwidth LSPs the single layer survivability is morecost-efficient. For the multilayer survivability we demonstrate that by mappingefficiently the spare capacity of the MPLS layer onto the resources of theoptical layer one can achieve up to 22% savings in the total configuration costand up to 37% in the optical layer cost. Further savings (up to 9 %) in thewavelength use can be obtained with the integrated approach to networkconfiguration over the sequential one, however, at the increase in theoptimization problem complexity. These results are based on a cost model withactual technology pricing and were obtained for networks targeted to anationwide coverage.
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