Research On Survivability Of Dual Faults In Elastic Optical Networks

With the rapid development of technologies such as Internet of Everything,Cloud Computing,and Video Surveillance,people's demand for high bandwidth has made the growth trend of traffic in communication networks intensified.The traditional Wavelength Division Multiplexing(WDM)optical network follows the fixed grid standard allocation method,which causes serious waste of spectrum resources in the allocation of fine-grained service resources.For the above problems,the researchers have proposed an efficient Elastic Optical Networks(EONs)with flexible resource allocation capabilities.Since the fiber link in the network carries huge communication traffic,the loss caused by the failure of a single fiber link cannot be ignored,let alone double failures.Therefore,survivability research is very important for optical networks.The technologies for ensuring the survivability of optical networks are mainly divided into protection technologies and recovery technologies,the two technologies have their own advantages and disadvantages.Based on the protection and recovery technology,the thesis studies how to improve the survivability of services in EONs under double faults.Firstly,due to the variety of services and the waste of resources caused by a single protection mode,the traffic in EONs is easy to block,in order to solve this problem,a double fault protection algorithm based on self-falling protection level is proposed in the third chapter.The algorithm comprehensively considers the transmission path distance,link load and idle resource status,so the most suitable transmission path can be selected for the request under the premise of balancing the link load;When calculating and allocating protection resources for request,there are three protection levels according to service requirements,namely,dual protection path shared protection,partial protection,and no protection.Different levels of protection strategies are selected according to the type of arriving service,if the available spectrum resources of the current network are insufficient to support the implementation of the protection policy at this level,the protection level is automatically reduced.The simulation results show that the proposed algorithm reduces the bandwidth blocking rate and improves the spectrum resource utilization of the network.Secondly,the failure of protection measures under the double faults also causes the traffic to be blocked,and the difference in the probability of link failures makes the protection resources configured for some services idle.In view of the above problems,the fourth chapter of the thesis proposes a path segmentation recovery algorithm based on pre-release of redundant protection resources.First,it is determined whether the probability of the transmission and protection path concurrent failure is within the maximum concurrent failure probability that the service can tolerate,then the service transmission completion degree is calculated according to the transmission time,and only when the two conditions are satisfied at the same time,the idle protection resources of service in the transmission can be pre-released.When traffic congestion occurs in the network,the Dijkstra algorithm is used to reroute the request,the minimum frequency slot required for the current service transmission is used as the fragment reference,and the spectrum fragment metric coefficient of each link is calculated to determine the link position with the maximum metric coefficient.The path is segmented according to the number of rerouting links and the position,and resources are matched using different modulation formats in each sub-segment to restore the transmission of the service.The simulation results show that the proposed algorithm can effectively improve the recovery rate of blocking service.