Node-Selective Cross-Layer Routing for Delay-Differentiated Services in Fine-Grained Optical Transport Networks

Fine-grained optical transport networks (fgOTNs) have attracted increasing interest in recent years for their ability to deliver small-granularity services with high flexibility and efficiency. To further improve the performance of fgOTNs in delivering small-granularity services having diverse delay requirements, this paper proposes and investigates a node-selective cross-layer service routing (NSCR) algorithm. By selecting a path based on both wavelength occupation and the quantity of currently active services that can be aggregated in the last optical hop, and by selecting proper intermediate nodes to participate in fgOTN layer exchange and aggregation under service delay constraints, the service blocking rate is reduced and resource utilization is maximized. Further, a variation of the proposed NSCR scheme is investigated that incorporates load balancing by selecting a path based on wavelength occupation, currently active service routes, and the remaining bandwidth. The performance of the two schemes is evaluated under both the NSFNET and Cost239 topologies, and the results demonstrate the superiority and effectiveness of the proposed schemes in terms of wavelength utilization rate and service blocking rate while satisfying the diverse delay requirements of different services.