Fragmentation-aware algorithms for multipath routing and spectrum assignment in elastic optical networks

Elastic optical networks have been highlighted for attending to large volumes of data with different transmission rates. To meet high transmission rates, you need to troubleshoot RMLSA (Routing, Modulation Level, Spectrum Assignment) which is to select a route, choose a modulation level and a range of free spectrum. In the context, this paper we present a new RMLSA algorithm aware of the physical layer effects using the fuzzy system to assist in choosing the best route in elastic optical networks, called Fuzzy-RQoTO. The proposed algorithm selects the route of best quality for a given pair (o, d) considering metrics the relative fragmentation and number of occupied slots. The Fuzzy-RQoTO algorithm attempts to reduce the blockage caused by the degradation of the transmission quality of the optical circuits and concomitantly selects a best route for the establishment of the circuit. A performance evaluation study was performed on the NSFNet and EON topologies comparing the performance of the Fuzzy-RQoTO algorithm with three algorithms already proposed in the literature. The Fuzzy-RQoTO algorithm presented a minimum gain of 27.5% in terms of circuit blocking probability. In terms of bandwidth blocking probability, Fuzzy-RqoTO reported a minimum gain of 21.9%.

Routing and Spectrum Assignment is a key issue in Elastic Optical Networks (EON). Under dynamic traffic conditions, spectrum fragmentation of the frequency resources reduces the spectrum utilization efficiency, and hence degrades the service blocking probability. To address this problem, this paper proposes an improved fragmentation aware routing and spectrum assignment algorithm (FA-RSA) for EON by considering the spectrum fragmentation in the routing decision and spectrum allocation phase. Theoretical analysis and numerical simulation results show that compared with the traditional Random-Fit (RF) and First-Fit (FF) algorithm, the improved algorithm can significantly reduce the blocking probability and improve spectrum utilization.

In this paper, we propose a defragmentation based load balancing technique for efficiently undertaking routing and spectrum assignment (RSA), and minimizing the fragmentation problem in elastic optical network (EON). In EON, after connections terminate, they leave behind spectrum gaps which con not be re-assigned. To counter this condition, in Defragmentation based Load Balancing Routing and Spectrum Assignment (DLBRSA), the existing connections are reconfigured. At the time of defragmentation, for route selection, among the available shortest routes, the route with the largest chunk of contiguous frequency slots (FSs) is chosen. DLBRSA has three advantages over the conventional Shortest Path RSA (SPRSA) technique: (1) defragmentation increases the network resource utilization, (2) load balancing on the basis of the largest available FS chunk along the route ensures uniform spectrum allocation, and (3) defragmentation ensures that the route length of the request is minimum. The performance of the DLBRSA is analyzed in reference to a benchmark, SPRSA strategy. The comparison is done on the metrics of bandwidth rejected, and the percentage of total network capacity allocated for the EON and NSFNET network topologies. These two parameters are evaluated under the two scenarios of increase in: network load (in Erlang) and number of FSs demand. Simulation results show lower bandwidth blocking probability of DLBRSA from 6.53% to 8.96% under the different load conditions. In addition, decrease of network resource utilization is observed, when we compare the proposed DLBRSA with SPRSA the existing strategy.

In elastic optical networks (EON), routing, modulation selection, and spectrum assignment (RMSA) is crucial in provisioning connection requests. Multipath RMSA offers a number of benefits including provisioning of ultra-high bandwidth demands and better utilization of fragmented spectrum resource. By Combining with traffic grooming, multipath RMSA and traffic grooming is able to provide better utilization of network resource in provisioning connection requests. Adding multi-hop routing mechanism to multipath RMSA and traffic grooming increases the flexibility for selecting paths resulting in higher probability of successfully finding routing paths for connection requests. Dynamic multipath RMSA problem in EON has been investigated extensively in the literature. Dynamic multi-hop multipath RMSA and traffic grooming problem in EON is far from been well studied. This paper proposes an algorithm for the dynamic multi-hop multipath RMSA and traffic grooming problem in OFDM-based elastic optical networks with sliceable bandwidth-variable transponders. Performance of the proposed algorithm is studied via simulation. Our simulation results show that the proposed algorithm yields lower bandwidth blocking ratio than an existing algorithm.

In this paper, we propose to investigate the RMSA (Routing Modulation and Spectrum Assignment) problem for connection requests on elastic optical networks (EON) by examining the selection of standard frequency blocks (SFB) from available frequency slots (FS) based on a set of source and destination nodes, also known as an Advanced Reservation (AR), and the impact of Resource Periodic Arrangement (RPA), which is a decision block on a connection request path that has both idle or busy data traffic, including a combined minimum Standard Frequency block (SFB). We also propose method ARRPA, a combination method that achieves more efficient results in increasing the number of connection requests as well as the impact of the amount of information to be distributed better, preventing greater blocking of connection requests. In comparison to previous work, the blocking probability is proportional to simulation within the available spectrum, modulation, and distance, with the simulation result being lower than 0.0204.

A brief review of protection based routing and spectrum assignment in elastic optical networks and a novel p-cycle based protection approach for multicast traffic demands

The routing and spectrum assignment problems in elastic optical networks are well-known NP-hard problem, and are even more complex and challenging when the energy consumption is taken into account. To tackle this challenging problem, we establish a bi-level programming model with the energy consumption of the optical networks and the maximum index of used frequency slots as the leader’s and follower’s objectives to be minimized, respectively, which are used to determine the optimal schemes of routing and spectrum assignments. To solve the model effectively, a hybrid genetic algorithm framework integrating a heuristic algorithm into a genetic algorithm is proposed. We use heuristic algorithm to sort the connection requests and design a genetic algorithm with tailor-made crossover, mutation and local search operator to look for an optimal routing and spectrum assignment scheme. Finally, simulation experiments are conducted, and the experimental results indicate the effectiveness of the proposed model and algorithms.

A constrained-lower-indexed-block spectrum assignment policy in elastic optical networks

Spectrum Expansion/Contraction and Survivable Routing and Spectrum Assignment problems on EONs with time-varying traffic

Study and Analysis of Routing and Spectrum Allocation (RSA) and Routing, Modulation and Spectrum Allocation (RMSA) Algorithms in Elastic Optical Networks (EONs)

Extending light-trail into elastic optical networks for dynamic traffic grooming

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.

This paper presents the features of an advanced software simulator for the Elastic Optical Network (EON) - Complex Elastic Optical Networks Simulator (CEONS). The CEONS is as a test environment for solving three main issues addressed in EON: Routing and Spectrum Assignment (RSA) problems; Routing, Modulation and Spectrum Assignment (RMSA) problems, and addressing regenerator placement problem. With a universal API, users can design their own algorithms in any programming language and implement them in the simulator as plugins to solve the problems mentioned above. The ease and versatility of implementing the algorithms allows usage of the CEONS in advanced problems and for the introduction of EON technology.

This paper considers distance adaptive dynamic routing and spectrum assignment (RSA) for elastic optical networks with shared backup path protection (SBPP). Efficient heuristic algorithms based on spectrum window planes are proposed for implementing distance and modulation format adaptive RSA so as to maximize spare capacity sharing among multiple protection lightpaths. A differentiated sharable frequency slot cost was also defined for the first time to more efficiently share protection resource. Network performance is evaluated in terms of bandwidth blocking probability (BBP) through simulations. The proposed SBPP technique is effective in reducing BBP and improving spectral efficiency compared to conventional SBPP schemes and 1+1 path protection. The impact of transponder tunability on bandwidth blocking performance is also evaluated to show that a limited tuning range is sufficient to achieve a BBP performance close to that with full tunability.

Power, routing, Modulation Level and Spectrum Assignment in all-optical and elastic networks