Research Of Survivability Technologies For Future Transport Networks

With the development in flexible bandwidth allocation and the widely applied optical networking technologies for datacenter operations, optical networks itself become high-capacity, complicated and geographically distributed. With the frequent occurrence of natural disasters such as earthquake, hurricane, tsunami, tornado, human-made faults and the use of weapons of mass destruction in regional conflicts, the survivability technologies against multi-faults have become research focus in optical networks. The survivability technologies against multi-faults mainly involve the multi-faults monitoring, identification and localization, multi-faults tolerance, protection and fast restoration, etc. Targeted on the survivability demands in optical networks under multi-faults and supported by the973basic research sub-topics:the research of survivability technologies for high-capacity optical networks against multi-faults, this paper studies the multi-faults localization protocol, the fuzzy fault set based multi-faults restoration mechanism, three-dimensional protection mechanisms and multi-faults tolerant technology. We obtain a number of innovative research results on these topics.In this paper, we propose the fuzzy fault set and k-regular and k-connected structures. We apply the fuzzy fault set into multi-faults localization and restoration, and use the k-regular and k-connected structures to provide protection against multi-faults. The details include the following three aspects:The first, in the aspect of multi-faults localization, we analysis the operating principle of traditional fault localization algorithm and establish the mathematical model for multi-faults localization, and then we propose the fuzzy fault set based multi-faults localization mechanism. The problem of locating multi-faults has been proved to be NP-complete, so we modify the objective function of multi-faults localization in traditional localization mechanism into obtaining the fuzzy fault set which includes all the possible failed elements in the optical networks. Each element in the fuzzy fault set is assigned to a grade of membership which represents the degree of the risk of fault. We design the detailed protocol process and fuzzy fault set based construction algorithms for application in high-capacity optical networks. Simulation results show that fuzzy fault set based multi-faults localization mechanism can greatly reduce the complexity of multi-faults localization.The second, in the aspect of multi-faults protection, we apply Menger’s theorem into protection structure design against concurrent multi-faults and proposed the k-regular and k-connected structure based three-dimensional protection mechanisms. Toward the k-connected structure, it contain k internally independent paths between any two nodes hence it can handle concurrent k-1failures. In order to use the minimal spare resources in protection structure, the degree of each node is required to be the same. Theoretical results show that a k-regular and k-connected structure is the optimal protection structure in link-restorable mesh networks under multi-faults. The linear programming model (ILP) for k-regular and k-connected structure, a construction method for k-regular and k-connected structure design and the node model are also proposed. Numerical results indicate that the spare capacity efficiency of k-regular and k-connected structure can reach the lower bound in static networks. And it can largely improve spare capacity efficiency compared with p-cycles based protection structure without reducing recovery rate under dynamic traffic.The third, in the aspect of multi-faults restoration, we propose the fuzzy fault set based two-stage restoration mechanism take advantage of the membership function of each element in fuzzy fault set and the set operations. The proposed restoration mechanism calculates the fault risk for each recovery path. It contains the stage of restoration and re-restoration. In the stage of restoration, we calculate the membership function of each recovery path which presents the reliability and make best effort to recovery the failed light-path using the risk resource in the fuzzy fault set. In the stage of re-restoration, we rebuild some working light-path and update the fuzzy fault set in order to recovery the remaining failed light-paths. Numerical results show that the proposed two-stage restoration mechanism achieves a higher stability and success rate.