Distributed Optical Control Plane Architectures for Handling Transmission Impairments in Transparent Optical Networks

Transmission impairments in wavelength-division- multiplexing (WDM) transparent optical networks accumulate along an optical path and determine the feasibility of lightpaths; hence, the impairments need to be managed efficiently by the control plane. This paper presents impairment-aware distributed optical control plane (OCP) based on enhancements to resource reservation protocol-traffic engineering (RSVP-TE) signaling protocol (S-OCP). In particular, four architectural options [K-sequential (K-SEQ), K-parallel (K-PAR), hop-by-hop (HbH), and full flooding (FF)] within the S-OCP approach are defined and compared. Simulation results show that a combination of HbH routing and feasibility check can be considered as a good compromise both in terms of blocking probability and control plane overhead. The feasibility of a signaling-based approach for the control plane is further demonstrated by comparing simulation results with the results obtained from the implementation of the proposed architectural options in a commercial generalized multiprotocol label switching (GMPLS) protocol emulator. Furthermore, we argue that the real networks will rarely be homogeneous concerning transponder types, creating the need for a transponder selection policy at the end nodes. We introduce and compare two policies: best-first and worst-first. The results obtained from our experiments show that a worst-first policy for selecting transponders can save up to 50% enhanced transponders thereby reducing the overall cost.