Survivability Against Multi-Link Failure In Elastic Optical Networks

The development of Internet is rising with the service requests. As the infrastructure of Internet, optical network has two important trends: the topology is more complex and the bandwidth is larger. Because the nature and man-made disaster is more frequent than before, the survivability of optical network is also more important. Complex network will increase the probability of multi-link failure; while the bandwidth will enlarge loss of users. The traditional survivability technologies (active monitoring for failure localization, pre-configured cycle, failure management system, et al.) are designed for single-link failure. Although they are extended to multi-link failure scenario, it still have the problems, as low accuracy of failure localization, high redundancy of protection resource, and complex management for repair. Hence, how to minimize network resources to recover the failed services and network by multi- link failure is the most important problem in the field optical network.In this work, several technologies are proposed to deal with multi-link failure in elastic network. The problem is divided as failure locatlization, failure protection, and failure recovery. This work first analyzed in theory, and then structured the mathematic model, finally simulated it to evaluate the performance of the solutions. The main innovative research achievements are listed as follows:Firstly, for the transparency of all-optical network and the model of traditional monitor model, a new monitor model which can be actively turn on or off by the controller is designed, and a fusion failure location algorithm are proposed based on the status of lightpath of working and monitoring services. In the algorithm, the status of lightpath of working service are firstly analyzed to find the suspected failed link set; and then,monitoring services are set up in each suspected failed link to accurately find the failure locations. The results show that the accuracy of fusion failure location algorithm is 10% higher, and the localization time is half than the traditional algorithm.Secondly, for the high node dimensionality and limited bandwidth resources in optical networks,based on the theory of connectivity and Menger Theorem, pre-configured cube (p-Cube) protection structure is proposed to protect multi-link failure. In pre-con figured cycle (p-Cycle)protection structure, it composed as a plane by the cycle and straddling links; p-Cube is originated from p-Cycle, which is a closed structure composed by cycle. The redundancy resources are assigned only on the links of cube, so that it can reduce the dimensionality of protection structures and the redundancy resources. Based on the theory of p-Cube,pre-configured prism (p-Prism) and pre-configured ball (p-Ball) are proposed with the algorithms of strcture construction, resource allocation,and path routing. Simulation results show that, compared with p-Cycle, p-Cube can reduce the compustion of protection link and resources, and has better performance in hops of protection path and protection rate.Thirdly, for the service in data center and elastic optical network,bandwidth-adaptability protection with content connectivity (BCP). In data center network, operator should provide content instead a special destination node for the users; in the elastic optical network, the allocation of spectrum is more flexible. In this work, the content connectivity of data center network and the bandwidth squeeze in elastic optical network are combined as the BCP. In the path routing, the data center nodes with special content are all the candidate destination nodes; in the resource allocation,the bandwidth and modulation are selected by the level of request.Simulation resoutls show that, compared with content connectivity algorithm without adaptive, BCP can reduce the blocking ratio of the network.Forthly, for the network virtulization (NV), multi-link failure recovery is proposed to reduce the damage of services. The emergence of NV makes the request from point-to-point request to virtual network which is composed of several virtual nodes and links. Failed virtual links and disconnected virtual networks are employed to evaluate the damage of virtual networks. In this work, based on the number of repair teams and location of failures, the damage model of virtual network is established and the repair solution is proposed. Simulation results show that, the proposed algorithms can provide reasonable solution for network operators to repair optical networks after multi-link failure.