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In this paper, we propose a novel hybrid strategy that combines mixed integer linear programming (MILP) formulation with different alternative routing approaches that is capable of solving, simultaneously, the routing, modulation format and spectrum assignment problem in the design of elastic optical networks. We extend our proposal to a path-link formulation that, although it is not guaranteed to find the optimal solution, it has shown reasonable solutions within inferior simulation time, allowing it to be used in not very short networks. We also compare our proposal with another MILP formulation and three adapted heuristics, all available in the literature. The results show the benefits of our proposal considering diverse simulation scenarios and different number of modulation formats over 19 realistic networks in terms of simulation run time and maximum number of used set of slots.

An elastic optical network (EON) plays an important role in transport technology for virtualization of networks. A key aspect of EONs is to establish lightpaths (virtual links) with exactly the amount of spectrum that is needed and with the possibility of grooming, the process of grouping many small traffic flows into larger units, creating a super-lightpath. Grooming eliminates the need for many guard bands between lightpaths and also saves transceivers; however, it often leads to the need to perform optical–electrical–optical conversions to multiple-data-rate optical signals at intermediate nodes. The aim of this paper is to provide a mixed-integer linear programming (MILP) formulation, as well as heuristic and meta-heuristic approaches, for the design of multiple virtual optical networks (VONs) in an elastic optical substrate network with bandwidth-variable lightpaths, modulation format constraints, and virtual elastic regenerator placement. Traffic grooming is allowed inside each VON, and a distance-adaptive modulation format technique is employed to guarantee efficiency in terms of bandwidth for a physical substrate, subject to several virtual topologies. A reduced MILP formulation without grooming capability is also proposed for comparison. The complete MILP formulation jointly solves the virtual topology design, regenerator placement, and grooming problems, as well as the routing, modulation, and spectrum assignment (RMSA) problem. The reduced MILP formulation, heuristics, and meta-heuristic, on the other hand, separate the virtual topology design problem from the RMSA problem. It is shown that the grooming approach can provide good results, since it solves the problem for a complete design when compared to the approach without grooming. Furthermore, heuristic solutions for large networks are proposed, which present good performance (in terms of saving spectrum) for the design with large instances.

In Elastic Optical Networks (EON), the problem of routing and spectrum Allocation (RSA) has been solved along the years through the use of optimization techniques or heuristics, with the aim of minimizing the use of network resources or maximizing the capacity for future requests. The effects of the physical layer in the RSA problem are of fundamental importance given that there is a distance limitation with the required bit rate and modulation format used to transmit the signal. On considering the linear and non-linear noise effects, it is possible to include quality of transmission (QoT) in the optimization process. In this paper, we propose a modification to a traditional heuristic for the RSA problem in Elastic Optical networks to consider both effects of the physical layer. The proposed modification takes into account the channel input power and SNR Margin to choose all modulation formats and to assign resources. The main goal is to increase the spectral efficiency and throughput of the channels by mitigating blockages in the physical layer. Simulations were performed for various topologies, and the results suggest advantages in terms of number of blocked channels and spectrum usage of the new proposal in relation to the traditional BSR heuristics.

This paper proposes heuristics, which can maximize the number of remaining available routes and minimize the number of transceivers used in Elastic Optical Networks (EON). The aim of the proposal is to preserve the open capacity for the accommodation of future unknown dynamic demands. Case studies are carried out in order to analyze the performance of the heuristics over two networks. The results suggest that it is feasible to preserve enough open capacity to avoid blocking of future requests in EON with scarce resources.

With network virtualization, the physical infrastructure can be partitioned into multiple parallel virtual networks for sharing purpose. However, different transport technologies or Quality of Service (QoS) levels may impact in both the requested amount of resources and the characteristics of different virtual instances that can be built on top of a single physical infrastructure. In this paper we propose a novel Mixed Integer Linear Programming (MILP) formulation for different schemes of protection in scenarios where multiple virtual topologies run over an elastic optical network. The proposed MILP formulation uses the concept of bandwidth squeezing to guarantee a minimum bandwidth for surviving virtual topologies. It achieves a high level of survivability for the traffic that is subject to a different committed service profile for each virtual topology. Case studies are carried out in order to analyse the basic properties of the formulation in small networks, and three heuristics are proposed for larger networks.