Efficient wavelength rerouting in WDM single‐fiber and multi‐fiber networks with and without wavelength conversion

Article type: Research Article

Authors: Mohan, G. | Murthy, C. Siva Ram

Affiliations: Department of Computer Science and Engineering, Indian Institute of Technology, Madras‐600 036, India E‐mail: {gmohan@hpc.,murthy@}iitm.ernet.in

Abstract: In this paper, we consider wavelength rerouting in circuit switched wavelength‐routing Wavelength‐Division Multiplexed (WDM) networks. We address the rerouting issue and propose rerouting algorithms for single‐fiber and multi‐fiber networks with and without wavelength conversion. The wavelength continuity constraint imposed by WDM networks leads to poor blocking performance. The blocking performance can be improved by wavelength rerouting and by providing wavelength conversion capability at the routing nodes. Wavelength rerouting rearranges certain existing lightpaths to accommodate a new connection request. The wavelength continuity constraint is relaxed at the routing nodes having wavelength conversion capability. Since the number of technologically feasible wavelength channels per fiber is very few (up to 16), multi‐fiber networks have become an attractive alternative which can support increased traffic with improved performance [3]. Recently, in [1], a rerouting scheme called ‘Parallel Move‐To‐Vacant–Wavelength Retuning (MTV–WR)’ with many attractive features such as shorter disruption period and simple switching control, and a rerouting algorithm, for this scheme, to minimize the weighted number of rerouted lightpaths have been proposed. The algorithm runs in polynomial time, but is not time optimal. We present here a time optimal rerouting algorithm to minimize the weighted number of rerouted lightpaths. We also present a rerouting strategy with the same computational complexity for the networks with sparse wavelength conversion. We discuss, how the parallel MTV–WR scheme can be extended to the networks with sparse wavelength conversion for rerouting sub‐lightpaths. We also discuss how this scheme can be modified for multi‐fiber networks, wherein a lightpath can be moved to a vacant wavelength on any vacant fiber in the bundle of fibers, while maintaining the route. We extend the rerouting algorithm for the single‐fiber networks to the multi‐fiber networks with the above modified rerouting scheme. The performance of the proposed algorithms are evaluated through extensive simulation. The results show that the proposed algorithms improve the blocking performance significantly.

Journal: Journal of High Speed Networks, vol. 8, no. 3, pp. 149-171, 1999