Restoration in all-optical GMPLS networks with limited wavelength conversion
A new generation of optical components and the advance of the Generalized Multi-Protocol Label Switching (GMPLS) control plane supporting dynamic provisioning and restoration of optical connections (i.e., lightpaths), brings the vision of the dynamic all-optical network closer to reality. An emerging technology is the conversion between wavelengths, which removes the wavelength continuity constraint, thus allowing an easier and more flexible connection allocation. A limitation in the number of wavelength converters impairs their benefits especially during the restoration phase, when many simultaneous recovery attempts must share residual resources. This paper investigates the restoration performance of GMPLS-controlled all-optical networks with limited wavelength converter deployment. We investigate how different restoration methods, namely span restoration, segment restoration, and end-to-end restoration are affected by the availability of a limited number of wavelength converters at each node. For this purpose an enhanced wavelength assignment scheme compliant with GMPLS signaling is exploited, aiming at saving converters by assigning a higher preference to wavelengths not requiring conversion. An extensive simulation study has been conducted comparing the performance of this scheme to the most advanced scheme based on standard GMPLS signaling for the three restoration methods. Simulation results show that the enhanced wavelength assignment scheme significantly reduces the number of wavelength converters (WCs) necessary to achieve good recovery performance. The enhanced scheme especially improves span restoration performance, where the matching between the stubs' and recovery segment wavelength may require a WC. End-to-end restoration is the least affected, due to a higher degree of freedom in the route choice, while segment restoration performance lies in between.