Nowadays, most optical network planning strategies route the users by the shortest paths. However, balancing the network paths may achieve remarkable savings by using network resources as even as possible. In this work, we propose a balancing routing strategy for elastic optical networks (EON) architectures with static network operation, called Bandwidth-Balanced (BB). We compute the connection paths balancing the number of FSUs demanded in all network links, contrary to the users balancing strategies found in the literature. To evaluate our proposal, we perform the Routing, Modulation Level, and Spectrum Assignment problems (RMLSA), taking into account physical-layer impairments (PLI) found in optical communications. Experimental results show that the BB strategy outperforms commonly used strategies in capacity savings and spectral fragmentation.

In this paper, we propose a simulation-based strategy to solve the routing and spectrum assignment problem in elastic optical networks with a static network operation for ring network topologies. First, the proposed method arrange the network users decreasingly according to their bandwidth demands. Next, we introduce the Spiral policy to allocate the frequency spectrum. This policy consists of assigning the resources to the user in a correlative manner, following a spiral, taking advantage of the ring topology. Remark that each user path is fixed, computed by any shortest path algorithm. We assess the performance and robustness of our model by comparing the proposal with two optimization models in small rings (5-8 nodes) and with the most referenced methods found in the literature for larger ring networks (5-50 nodes). The results show that consistently our method outperforms the ones proposed in the literature, in terms of network cost and fragmentation.

This paper proposes a new method to compute alternate routes for multiple fault tolerance on Dynamic WDM Optical Networks. The method allows to obtain all the paths that replace the primary routes affected by one or several failures. Additional paths, called secondary routes, are used to keep each user connected to the network, including cases where multiple simultaneous link failures occur. The method also allows to obtain the number of wavelengths in each link of the network, computed such that the blocking probability of each connection is less than a pre-defined threshold (which is a network design parameter), in spite of the occurrence of k simultaneous link failures, with k ≥ 1. The solution obtained by the new algorithm is significantly more efficient than the result of applying current methods, its implementation is notably simple and its on-line operation is very fast.

Markov reward models have been employed to obtain performability measures of computer and communication systems. In these models, a continuous time Markov chain is used to represent changes in the system structure, usually caused by faults and repairs of its components, and reward rates are assigned to states of the model to indicate some measure of accomplishment at each structure. A procedure to calculate numerically the distribution of the reward accumulated over a finite observation period is presented. The development is based solely on probabilistic arguments, and the final recursion is quite simple. The algorithm has a low computational cost in terms of model parameters. In fact, the number of operations is linear in a parameter that is smaller than the number of rewards, while the storage required is independent of the number of rewards. We also consider the calculation of the distribution of cumulative reward for models in which impulse based rewards are associated with transitions.