| Summary: | 碩士 === 國立交通大學 === 網路工程研究所 === 103 === The Software-Defined Network (SDN) is a new kind of network architecture that separates the control plane from the data plane. In the SDN network, using only one controller has the single point of failure (SPOF) problem. Therefore, multiple SDN controllers are adopted. Several existing multiple controller failover mechanisms, which include failure detection and failure recovery, have been proposed to resolve the failure problem of multiple controllers, but they have some shortcomings. First, a distributed file system management tool, Akka, was adopted by a multiple controller architecture, Opendaylight. However, the Akka judges a controller failure by using only one controller, so it has a high false positive rate during controller failure detection. Second, during switch reassignment, existing controller failure recovery mechanisms cannot reduce overall switch-controller delays and balance controllers’ load at the same time. In this thesis, we propose a Fast and Load-aware Controller Failover (FLCF) for SDNs to resolve the above problems. In failure detection, the proposed FLCF utilizes one detecting controller to collect all the other controllers' failure notifications about a failed controller so as to help the detecting controller to make the final decision. In failure recovery, each controller pre-computes its recovery plan (switch reassignment plan) and synchronizes the plan with other controllers that will take over the switches if the controller is determined failed. The proposed FLCF uses a genetic algorithm to derive a best switch reassignment for a failed controller. Simulation results show that the proposed FLCF has better performance in terms of failover time and controllers load standard deviation than the related works. Under the same false positive rate during failure detection, the proposed FLCF reduces 15.7% failover time compared to FCF-M. In failure recovery, the proposed FLCF achieves the best controllers load balancing compared to all related works except the Survivor. However, the Survivor has longer switch-controller delay than the proposed FLCF after switch reassignment. In summary, the proposed FLCF has less failover time compared to FCF-M. After switch reassignment, FLCF can achieves lower average switch-controller delay and better controller load balancing, compared to the related works.
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