Cisco Huawei Technologies Cisco Huawei Technologies Huawei Technologies Impairment-Aware (IA) Routing and Wavelength Assignment (RWA) function might be required in Wavelength Switched Optical Networks (WSON) that already support RWA. This document defines proper encoding to support this operation. It goes in addition to the available impairment-free WSON encoding and it is fully compatible with it. As the information model, the encoding is independent from control plane architectures and protocol implementations. Its definitions can be used in related protocol extensions.