Routing and spectrum allocation in elastic optical networks under unicast and multicast traffic: A survey

Several lightpaths can be switched as a single entity, so that only one pair of transmission ports will be consumed at every intermediate node, which facilitates port savings in Wavelength-Division Multiplexing (WDM) optical networks. However, in Elastic Optical Networks (EONs), the lightpath does not occupy a fixed wavelength but a group of continuous and orthogonal subcarriers with the flexible bandwidth provisioning adjusted under the distance adaptive modulation. This means that the waveband switching in EONs involves the multi-dimensional allocation of the subcarrier, wavelength and even waveband, with the high dynamic. In this paper, to minimize the port cost and efficiently utilize spectral resources with the help of the complementary advantages of waveband switching and EONs, we propose the modulation-adaptive algorithm followed by a new waveband switching strategy. Simulation results demonstrate that our approach is cost-effective and improves the spectral efficiency of elastic waveband switching optical networks.

Elastic optical networks (EONs) are considered a very promising solution for next-generation optical networks. Elastic spectral bandwidth allocation promotes spectrum utilization efficiency and thus increases the network capacity. One of the fundamental problems in EONs is the routing and spectrum allocation (RSA) problem. Since real EONs may provide only a few regular line rates, we comprehensively study in this paper the dynamic RSA problem in EONs with several mixed line rates. To solve the dynamic RSA problem efficiently, we decompose the problem into RSA subproblems. For the routing subproblem, we propose an efficient multiconstrained routing algorithm named sorted feasible paths searching (SFPS) to find the shortest feasible paths for dynamic traffic demands. The completeness, optimality, and complexity of SFPS are proved. For the spectrum allocation subproblem, we propose two spectrum allocation strategies named fixed segmentation and adaptive segmentation to assign spectrum for the noncommensurate traffic demands of EONs with mixed line rates. Simulation results prove that the proposed dynamic RSA algorithms are time efficient and perform better than existing dynamic RSA algorithms in terms of bandwidth blocking probability and spectrum fragmentation ratio in EONs with mixed line rates.

This paper proposes an integer linear programming (ILP) formulation and an effective heuristic based on genetic algorithm (GA) for static routing and spectrum allocation (RSA) problem in spectrum-sliced elastic optical path network (SLICE). The RSA problem belongs to the class of problems called NP-Hard, and then approaches to achieve optimal solutions are limited to solve only small instances. For real networks optimal methods cannot give a solution in viable time, hence heuristic approaches are required. Then, we propose an ILP model and Genetic Algorithm (GA) to optimize the RSA problem in SLICE network. In spite of scalability problem an integer linear programming (ILP) formulation is presented, with the goal of attaining optima solutions for small networks and ascertaining our heuristic's efficiency. In addition, it is presented a detailed analysis for GA's parameters.

Due to the ever-increasing demand for the Internet, optical fiber networks are receiving a lot of attention. Elastic Optical Networks (EONs) have a potential future in next-generation high-speed networks due to their increased flexibility and better spectrum management. Moreover, Space-Division Multiplexing (SDM) is used to expand the fiber capacity further. One of the most difficult problems in elastic optical transport networks is the Routing and Spectrum Assignment (RSA). The goal of this study is to create and develop effective algorithm for internet traffic routing in SDM-based Elastic Optical Networks (EONs). The focus of this study is on a problem known as Routing, Spectrum, and Core Allocation (RSCA) for flex-grid SDM networks. Preliminary experimental results demonstrate good performance in terms of time and quality using an assignment-based heuristic.

Elastic optical network (EON) technology is considered as a very promising candidate for future high-speed networks due to its intrinsic flexibility and high efficiency in allocating the optical spectrum resources. The key issue that has to be addressed in EON is the routing and spectrum allocation (RSA) problem. RSA is NP-hard problem that has to be solved in an efficient manner. It is a highly challenging task particularly in the case of large problem instances. In this paper, we applied the bee colony optimization (BCO) metaheuristic approach to solve the RSA problem in EON with static traffic demands. The objective of the proposed BCO---RSA algorithm is to minimize both the network spectrum utilization and the average path length criterions. The results of numerous experimental studies show that our BCO---RSA algorithm performs superior compared to some benchmark greedy heuristics as well as to differential evolution (DE) metaheuristic algorithm recently proposed in the literature. The algorithm is evaluated in different realistic size optical networks, such as the NSFnet, two European optical networks (EON-19 and EON-28) and the USA network topology. Simulation results demonstrate that considerable spectrum savings could be achieved with our BCO---RSA algorithm compared to other considered approaches. In addition, we analyzed the efficiency of the BCO---RSA algorithm and compare it with the competitive DE approach according to the required CPU time and the convergence speed.

Elastic Optical Network (EON) or Flex-Grid network enables flexible assignment of spectral resources. With Orthogonal Frequency-Division Multiplexing (OFDM) technologies, the spectral resources for an end-to-end optical path can be allocated based on the modulation format and the optical reach in EON. The routing and spectrum allocation (RSA) algorithm in EON allocates enough sub-carriers along the spectrum path (SP) to satisfy the connection request. Due to the spectrum-continuity and sub-carrier consecutiveness constraints, an RSA algorithm may not have sufficient contiguous sub-carriers available along a single SP. Instead of using a single SP, in this paper, we propose a multipath RSA algorithm in EON called Modulation-aware Multipath Routing and Spectrum Allocation (MMRSA) algorithm in which the connection demands are satisfied using a minimum number of paths with distance adaptive modulation techniques. Simulation results demonstrate that the proposed MMRSA algorithm results in a lower blocking probability as compared to other existing multipath and single path RSA algorithms. Our study also shows that a combined usage of multipath routing and flexible distance-adaptive modulation techniques can reduce the blocking probability while consuming the number of sub-carriers similar to that of a single path routing algorithms.

Energy-efficient routing, modulation and spectrum allocation in elastic optical networks

With the development of science, technology and society, the demand for global communication bandwidth has been greatly increased, and it is difficult for traditional optical fiber networks to meet this growing bandwidth demand. In this context, elastic optical networks (EONs) have received a lot of attention from research and industry due to their allocation flexibility and efficient utilization. Among them, the complex routing and spectrum allocation (RSA) problem is one of the main problems currently studied in EONs, mainly to improve the efficiency and flexibility of different service transmissions by allocating a continuous number of sub-carriers. In this paper, a new variant of the RSA problem is proposed and a more concise integer linear programming formulation of the RSA problem is provided. Experiment results demonstrate that the proposed approach can achieve the expected results and substantially increase the bandwidth capacity of the network.

Adaptive routing and spectrum allocation in elastic optical networks

In this work, an eavesdropping-aware routing and spectrum allocation approach is proposed utilizing network coding (NC) in elastic optical networks (EONs). To provide physical layer security in EONs and secure the confidential connections against eavesdropping attacks using NC, the signals of the confidential connections are combined (XOR-ed) with other signals at different nodes in their path, while transmitted through the network. The combination of signals through NC significantly increases the security of confidential connections, since an eavesdropper must access all individual signals, traversing different links, in order to decrypt the combined signal. A novel heuristic approach is proposed that solves the combined network coding and routing and spectrum allocation problem that also takes into account additional NC constraints that are required in order to consider a confidential connection as secure. Different routing and spectrum allocation strategies are proposed, aiming to maximize the level of security provided for the confidential demands, followed by an extensive performance evaluation of each approach in terms of the level of security provided, as well as the spectrum utilization and blocking probability, under different network conditions. Performance results demonstrate that the proposed approaches can provide efficient solutions in terms of network performance, while also providing the level of security required for each demand.

Fixed alternate routing is a potential routing scheme for routing and spectrum allocation (RSA) in elastic optical networks (EON) which has less complexity and time consumption compared to adaptive routing scheme. However, adaptive routing scheme efficiently reduces the amount of network bandwidth blocking probabilities (BBPs) which uses traffic engineered paths and tunes according to the current network status. In this paper, an algorithm for routing is proposed for dynamic traffic in EON which works iteratively to arrange the pre-computed fixed alternate routes offline to incorporate link loading. During the offline process, the pre-computed routes are arranged with an objective to reduce link congestion and diverts lightpaths to the under-utilized links. The proposed scheme merges the properties of fixed alternate routing and adaptive routing and is utilized for dynamic traffic in EON. It has been shown through simulation results that the proposed scheme efficiently improves the performance of RSA in EON and reduces the amount of BBPs compared to the fixed alternate routing and an existing constrained-lower-indexed-block (CLIB) based adaptive routing algorithm. The proposed LCA greatly reduces congestion over all links during dynamic network operation and lowers congestion spikes over some links which occues in the existing alternate routing scheme in different network scenarios.

In this paper a routing and spectrum allocation in elastic optical networks has been presented. The algorithm is capable of switching between single and multipath routing and spectrum allocation. It also assigns modulation levels based on the distance and is aware of the differential delay in the network. An integer linear programming formulation has been proposed to solve the problem and result in better performance. A heuristic has also been proposed to serve the dynamic scenario in the network and improve the results compared with the previous works.

This paper focus on the routing, modulation level and spectrum allocation (RMLSA) problem in the next generation datacentre networks, which own the advantages of both Elastic Optical Networks (EON) and Software Defined Networking (SDN). We proposes an Integer Linear Programming (ILP) model for this problem. Simulation results show the ILP model achieves an outstanding load balancing performance.

Spectrum slicing-based fragmentation aware routing and spectrum allocation in elastic optical networks

Elastic optical networks (EONs) are being used to adapt to the recent rapid changes in traffic behavior and the exponential growth in bandwidth demand. Routing and spectrum allocation (RSA) is one of the most important determining factors of the design, performance, and operation of EONs. In this work, we propose an adaptive RSA algorithm based on the relative cost concept under which the transient effect when a call is admitted on a given route/spectrum set at a given network state is estimated. The algorithm computes the relative cost of forwarding an arriving call across all available route/spectrum sets to the destination. The algorithm selects the route/spectrum set with the least relative cost; if the minimum relative cost is more than the call’s value, the call is potentially rejected. In this study, the efficiency of using relative cost to solve the RSA problem is demonstrated via simulation.