A hybrid approach for provisioning sub-wavelength requests in IP-over-WDM networks

This paper deals with the provisioning of sub-wavelength requests in IP-over-WDM networks. Traditionally, these requests are either provisioned by setting up a lightpath switched transparently all the way from the source to the destination (Routing and Wavelength Assignment-RWA-provisioning), or by using one or more existing lightpaths with enough residual bandwidth to time-multiplex the new traffic. In this work an interconnection model between the IP and optical layers that allows all control information to be maintained under a single administrative domain (namely, the optical domain) is assumed. This enables hybrid provisioning, which makes use of existing lightpaths and lightpaths to be set up. Three hybrid algorithms are introduced, namely the Shortest Path First-Fit (SPFF), the Shortest-Path Exhaustive Search (SPES) and Network-Wide Exhaustive Search (NetWES), each differing in the way the hybrid paths are sought for. Simulation results indicate that all three perform better than the conventional overlay sequential routing, and NetWES performs better than the rest.