Research On Routing And Spectrum Allocation Of Elastic Optical Networks Based On Fragmentation-aware

With the rapid development of mobile Internet,cloud computing and Internet of things,the bandwidth demand is also increasing and the bandwidth granularity requirement is increasingly diversified.Traditional optical networks based on wavelength division multiplexing technology can only provide fixed bandwidth channel which can not meet the requirement of bandwidth granularity diversity.Elastic Optical Networks(EONs)are proposed to solve this problem.The flexibility of elastic optical networks in allocating spectrum resources can meet users'bandwidth diversity needs.A very important problem in EONs is Routing and Spectrum Allocation(RSA),which becomes a Routing,Modulation and Spectrum Allocation(RMSA)problem when the choice of Modulation modes on different paths is taken into account.In this paper,RSA and RMSA problems in fragment-aware elastic optical networks are studied,and then corresponding algorithms to reduce the blocking probability and spectral debris are proposed.Firstly,two RSA algorithms are proposed for RSA problem,namely Min-PCR algorithm and Min-LCR algorithm.The goal of the Min-PCRr algorithm is to minimize the reduction of path adjacency,while the goal of the Min-LCR algorithm is to minimize the sum of the reduction of the continuity of all links on the path.Through the simulation of NSF-Net and Cost239 topology,the proposed algorithm is compared with MUF-HG algorithm and First-Last-Fit algorithm.Simulation results show that Min-PCR algorithm and Min-LCR algorithm have lower blocking probability in high traffic.Then,an algorithm for RMSA problem is proposed.it always chooses the available spectrum block with the minimum metric.This algorithm contains three innovation points:(1)it uses a unique index(35)R_pto measure the resource reduction on the path.(2)when using frequency blocks on a path p,the resource reduction on all relevant paths is taken into account in the measurement.(3)the path hops are used as weights in the measurement to balance the unfairness among paths with different hops.Simulation results on NSF-Net and Cost239 show that the algorithm is superior to Block-Assignment algorithm and First-Last-Fit algorithm,which can significantly reduce the blocking probability and improve the fairness between different paths.In a word,three fragment-aware algorithms for routing and spectrum allocation in elastic optical network are proposed in order to solve the RSA problem and RMSA problem in elastic optical network.Through the simulation in network topology and comparison with the existing algorithms,good results are obtained.