We implement shared-path protection (SPP) with extra traffic in automatically switched optical network (ASON) rings provided with a generalized multiprotocol label switching (GMPLS) control plane. The protection time provided by the SPP scheme is analyzed as a function of the switching time of the wavelength-selective switches (WSS), the key components to building reconfigurable optical nodes. We demonstrate that the switching time of the currently available WSS prevents the protection of the complete set of affected label-switched paths (LSPs) within 50 ms after fault detection. Therefore, two alternative strategies can be considered, namely, (1) the definition of two classes of protection with different requirements in terms of protection time, and (2) a real-time mechanism to decide, on the basis of the current number of LSPs to protect, whether the protection scheme to apply is either at the path layer or at the link layer. When protecting at the path layer, part of the extra traffic will be saved, whereas all the extra traffic will be preempted when protecting at the link layer.
© 2009 Optical Society of AmericaPDF Article