Dynamic establishment of differentiated survivable lightpaths in WDM mesh networks
Computer Communications
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In this paper, we consider wavelength rerouting in circuitswitched wavelength-routing Wavelength-Division Multiplexed (WDM)networks. We address the rerouting issue and propose reroutingalgorithms for single-fiber and multi-fiber networks with andwithout wavelength conversion. The wavelength continuity constraintimposed by WDM networks leads to poor blocking performance. Theblocking performance can be improved by wavelength rerouting and byproviding wavelength conversion capability at the routing nodes.Wavelength rerouting rearranges certain existing lightpaths toaccommodate a new connection request. The wavelength continuityconstraint is relaxed at the routing nodes having wavelengthconversion capability. Since the number of technologically feasiblewavelength channels per fiber is very few (up to 16), multi-fibernetworks have become an attractive alternative which can supportincreased traffic with improved performance [3].Recently, in [1], a rerouting scheme called ParallelMove-To-Vacant-Wavelength Retuning (MTV-WR) with many attractivefeatures such as shorter disruption period and simple switchingcontrol, and a rerouting algorithm, for this scheme, to minimizethe weighted number of rerouted lightpaths have been proposed. Thealgorithm runs in polynomial time, but is not time optimal. Wepresent here a time optimal rerouting algorithm to minimize theweighted number of rerouted lightpaths. We also present a reroutingstrategy with the same computational complexity for the networkswith sparse wavelength conversion. We discuss, how the parallelMTV-WR scheme can be extended to the networks with sparsewavelength conversion for rerouting sub-lightpaths. We also discusshow this scheme can be modified for multi-fiber networks, wherein alightpath can be moved to a vacant wavelength on any vacant fiberin the bundle of fibers, while maintaining the route. We extend thererouting algorithm for the single-fiber networks to themulti-fiber networks with the above modified rerouting scheme. Theperformance of the proposed algorithms are evaluated throughextensive simulation. The results show that the proposed algorithmsimprove the blocking performance significantly.