| Summary: | 碩士 === 朝陽科技大學 === 資訊與通訊系 === 105 === With the technology of computer network grows rapidly, the quantity of data is increasing gradually. Thus, the system needs to take lots of time to process these big data. Under such a circumstance, a novel network environment called Software-Defined Network (SDN) is proposed and more popular in recent years. In contrast to the traditional network, the concept of SDN is divided into two layers which are control plane and data plane, and it mainly depends on the centralized controllers to connect with all switches. In this way, the switches in the data plane can focus on the packet forwarding, and the controllers in the control plane are in charge of network management. If the network manager needs to fix the network environment, the network manager can control the controllers with programmatic way. This can help to manage the network more efficiently and flexibly.
However, some problems will influence the network system working, such as out of the work, attacking by the hacker or program bugs. Namely, the faulty controller can forge the command arbitrary and let the flow table cannot update successfully to make the whole network break down easily. Thus, the fault-tolerance issue needs to be studied to increase the reliability and stability for the SDN network system. One of the most important algorithms of fault-tolerance issue is the Byzantine Agreement (BA) problem. The goal of BA problem is to ensure the non-faulty processors can make an agreement even when the faults persist.
Based on reason above, a new SDN environment called the Multi-Controller Overlay Groups (MCOG) where each device is managed by the controllers is proposed in this study. Besides, the degree of the faulty influence will be revised to define the different bound of fault tolerance in MCOG environment. Furthermore, the new protocol named Dynamic Multi-Controller Assignment protocol (DMCA) is proposed to solve the BA problem.
As a result, the proposed DMCA protocol can solve the BA problem with the minimum number of controllers and rounds of message exchange and can tolerate the maximum number of the faulty controllers in SDN network environment.
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