Research On Protection Methods Of Improving Reliability For Elastic Optical Networks

With the promotion of Internet of Everything,the backbone network is suffering unprecedented pressure and challenges.Elastic optical networks(EONs),based on optical orthogonal frequency division multiplexing(O-OFDM)technology,have emerged as a promising next generation intelligent optical network.In EONs,the flexible spectral bandwidth allocation and adaptive modulation format selection promotes spectrum utilization efficiency.However,more than 80 percent of the information is transmitted through optical networks,so a large amount of request interruption and data loss may be caused in the case of optical fiber link failure.Therefore,in order to improve the reliability of the network,it is necessary to study the survivability of EONs.Compared with restoration strategy,the protection strategy has a faster recovery time,and provide better reliability assurance for network.Consequently,the protection methods for improving reliability of EONs are the focus of this thesis.In order to address the problems of spectrum fragmentation and high redundancy of protection resources in the p-cycle protection,a genetic p-cycle combination protection strategy(GPCPS)based on improved genetic algorithm(IGA)is proposed for elastic optical networks.In GPCPS,an IGA is devised to optimize the basic cycles and find out an efficient p-cycle protection combination for protecting the whole optical topology.For reducing the number of spectrum fragmentations,a p-cycle configuration strategy,named link spectrum partition and p-cycle configuration(LSP-PC),is introduced to pre-configure the protection resources on the p-cycles.Meanwhile,the least traffic priority and first fit(LTP-FF)algorithm based on spectrum resources usage and path lengths-aware,is designed to select working path effectively.Finally,simulation results show that the proposed GPCPS can reduce the bandwidth blocking probability,and improve the spectrum resource utilization.Due to the high resource redundancy of full protection for request's multi-link failure in elastic optical networks,the strategy of minimum fault risk loss probability protection(MFRL-PP)is proposed to protect the request with high spectrum-efficiency.In MFRL-PP,a link cost function integrated considering the link payload and fault risk is designed to choose the protection lightpath,which has minimum fault risk and consumes a small amount of spectrum resource.When the minimum fault risk lightpath is unavailable for shortage of idle spectrum resource,for further reducing the failure risk of the probability protection lightpath,a minimum fault risk loss probability protection mechanism for the non-symmetrical flow is designed to split the flow into two sub-flows for easily selecting the protection branch lightpath with the minimum fault risk loss.Moreover,in order to reduce the number of spectrum fragmentations,a spectrum allocation strategy based on the maximum spectrum coincidence degree is put forward to allocate spectrum resource.The simulation results indicate that the proposed algorithm can improve the spectrum utilization,and provide a better tradeoff between the bandwidth blocking probability and fault risk degree.In order to improve the network's reliability of multi-link failures in elastic optical networks,the strategy of reliability oriented probability protection and backup reprovisioning(ROPP-BR)is proposed.In ROPP-BR,an adaptive adjustment working and protection link cost functions are devised to effectively select the alternative working and protection light-paths respectively which have high reliability and consume a small amount of spectrum resources in the multi-link failure.The cost functions sufficiently considers the spectrum resources consumption and the link failure probability for both working and protection paths.Meanwhile,in order to satisfy the differentiated reliability requirements,a reliability oriented probability protection mechanism is introduced,so the probability protection path can be configured flexibly.Moreover,when the request will be blocked,a backup reprovisioning method based on maximum clique,is put forward to reconfigure the protection paths and spectrum resources.The simulation results indicate that the proposed strategy can synthetically consider the performance of bandwidth blocking probability and service reliability,and effectively reduce the redundancy of protection resources.