A hybrid wavelength reservation scheme for large-scale optical networks

In wavelength-division multiplexing (WDM) networks, wavelength reservation protocols are employed to establish end-to-end lightpaths between source-destination node pairs. In this paper, we propose a new reservation scheme that is targeted for application in large-scale WDM core optical networks requiring wavelength-continuity, such as the CORONET Continental US (CONUS), initiated by DARPA. The proposed scheme is a hybrid between the source-initiated reservation (SIR) and destination-initiated reservation (DIR), and is designed to reduce the backward blocking due to contentions among concurrent set-up requests. In the scheme, the protocol first tries to reserve a suggested wavelength that is associated with the chosen lightpath as the set-up request is propagated from source to destination; if this reservation fails, the node before the destination then reserves a wavelength by using a prioritized selection and echoes the request back to the source. Simulation results show that the hybrid approach can reduce the blocking probability significantly. In addition, the impact of aggressiveness, that is, the number of wavelengths a single request attempts to select in the destination initiated phase, and how it should be set, are also studied in this paper.