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Elastic optical networking is a potential candidate to support dynamic traffic with heterogeneous data rates and variable bandwidth requirements with the support of the optical orthogonal frequency division multiplexing technology (OOFDM). During the dynamic network operation, lightpath arrives and departs frequently and the network status updates accordingly. Fixed routing and alternate routing algorithms do not tune according to the current network status which are computed offline. Therefore, offline algorithms greedily use resources with an objective to compute shortest possible paths and results in high blocking probability during dynamic network operation. In this paper, adaptive routing algorithms are proposed for shortest path routing as well as alternate path routing which make routing decision based on the maximum idle frequency slots (FS) available on different paths. The proposed algorithms select an underutilized path between different choices with maximum idle FS and efficiently avoids utilizing a congested path. The proposed routing algorithms are compared with offline routing algorithms as well as an existing adaptive routing algorithm in different network scenarios. It has been shown that the proposed algorithms efficiently improve network performance in terms of FS utilization and blocking probability during dynamic network operation. [ABSTRACT FROM AUTHOR]

Highlights • A hybrid routing scheme is proposed for routing in EON. • An optimizaton model is presented with heterogeneous bandwidth demands. • The proposed model maintains a minimum level of congestion on all links. • The proposed model is integrated with the spectrum allocation subproblem with the continuity and contiguity constraints. • The proposed RSA scheme helps to efficiently reduce network blocking probabilities. Abstract 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. [ABSTRACT FROM AUTHOR]

• A routing algorithm is proposed for elastic optical networks with mixed line rates. • Routing decisions are initially made based on the modulation scheme with high data rates. • A route with maximum idle FS is preferred in case of multiple routes with same modulation. • If a tie occurs further, routing decision is made based on minimum hop count. • The proposed algorithm considers the first-last-mixed-fit spectrum allocation. • The proposed algorithm minimizes fragmentation and increases path contiguity. In this work, an adaptive routing, modulation, and spectrum allocation (RMSA) scheme is proposed for dynamic traffic in elastic optical networks (EON) which allocates resources based on EON characteristics during the RMSA decision process. The proposed scheme selects a route from the set of available paths which efficiently utilizes available resources on all links during network operation stage. Initially, routes are determined from the set of available paths based on a feasible modulation scheme with higher data rates and requiring minimum contiguous frequency slots (FSs) as well as satisfying optical reach of the modulated signal. During the operation stage, routes between end pairs are determined from these preselected paths based on maximum idle FSs on a path. This increases resources utilization on the underutilized routes with maximum path contiguity and having minimum fragmentation. In case of tie among routes with similar numbers of maximum idle FSs, the proposed algorithm selects a path with minimum numbers of hops. Finally, the proposed routing algorithm is integrated with the proposed first-last-mixed fit spectrum allocation scheme which increases average path contiguity and reduces average path external fragmentation for connection requests with mixed line rates requiring contiguous FSs. Simulation results show that the proposed RMSA scheme efficiently reduces the amount of blocking probability, reduces average path external fragmentation, increases average resources utilization, and increases average path contiguity in different network scenarios compared to the existing minimum hop based routing and k-distance adaptive paths (KDAP) routing schemes. [ABSTRACT FROM AUTHOR]