Span Restoration in Optical Networks with Limited Wavelength Conversion

Next generation optical networks provide functionalities to dynamically provision and recover connections, while emerging technologies allow for the conversion between wavelengths. These devices are however expensive and hence it is likely that only few are deployed throughout the network. Accordingly, the unavailability of wavelength converters decreases the chance for successful connection establishment, especially in the recovery phase, where several restoration requests try to access a limited pool of resources. The recently proposed Suggested Vector scheme has been designed to perform converter-saving wavelength assignment in GMPLS networks. The converter saving property of the Suggested Vector is particularly desirable in span restoration, where the pre-failure path stubs have to be merged to the restoration path at the failure-adjacent nodes. In order to avoid wavelength conversion at the merging nodes, the wavelength of the connection stubs can be considered. In this study, we evaluate the recovery performance of the Suggested Vector scheme and a scheme exploiting standard protocol extensions only. The behavior of both schemes with a stub-aware extension for span restoration is also assessed. Our simulations show that the Suggested Vector scheme achieves a higher recovery performance than the standard scheme. Both schemes benefit from the stub-aware modification. The performance increase is especially predominant if few wavelength converters are available and at medium load ranges. Furthermore, we describe different scenarios to extend the Suggested Vector wavelength assignment scheme to multi-domain networks with focus on span restoration.