Auxiliary-Graph-Based Traffic Grooming with Hybrid Single/Multipath Routing in Mixed-Grid Optical Networks

During the brownfield migration process from wavelength division multiplexing networks to elastic optical networks (EONs), fixed-grid and flex-grid devices coexist in the network, resulting in mixed-grid optical networks (MGONs). To improve the resource utilization of MGONs, we propose an auxiliary-graph-based traffic grooming with hybrid single/multipath routing (ATGHR) algorithm for MGONs. Specifically, we propose a hybrid single/multipath routing (HSMR) scheme to reasonably split the connection request into multiple sub-requests with the aim of satisfying the different transmission capabilities of flex-grid and fixed-grid nodes and avoiding excessive connection division. Based on it, we formulate an integer linear programming (ILP) model using traffic grooming (TG) with the objective of minimizing the spectrum and transponder usage for static MGON scenarios. Moreover, for a large-scale MGON where the ILP model is not tractable, we develop an auxiliary graph (AG) to support better characterization of TG and distance-adaptive modulation in MGONs and present several TG policies for different purposes by adjusting the edge weights of AG. Based on the AG, we propose a heuristic algorithm combined with TG and HSMR to further improve resource utilization. Extensive simulations are conducted to evaluate our proposals. Simulation results show that the ILP model can achieve the best performance in a small-scale network. Moreover, in large-scale networks, different TG policies for the same algorithm can achieve different targets, and our ATGHR has the best bandwidth blocking ratio compared with two benchmark algorithms using the same TG policy.