Online service provisioning in elastic optical networks with hybrid algorithm for congestion aware routing and spectrum allocation

Elastic optical networks (EON) has received intensive research attraction due to its agile spectrum management in the underlying optical backbone infrastructure whose channels can be allocated on variable spectrum width. In this paper, a hybrid scheme is proposed for routing and spectrum allocation (RSA) in EON. An optimization formulation is modeled which takes into account the elastic bandwidth characteristics of optical paths as well as maintains a threshold congestion level on all links. The goal of the proposed model is to minimize the cost of using the network links which results in the minimum cost paths between node pairs. The proposed optimization model is solved offline in the initial stage to obtain routing information which is utilized for online traffic in the second stage. The proposed model is integrated with the spectrum allocation subproblem with the continuity and contiguity constraints. The computational time of the optimization model is shown to be in (time unit) seconds for different networks which is an acceptable time to obtain routing information in the initial stage. The proposed RSA scheme helps to efficiently reduce network blocking probabilities in different network scenarios as the optimization model manages to route traffic load to the underutilized links when the quality of service of lightpaths on the overutilized links meet the desired threshold congestion level.