| The current Internet has become one of the world’s most widely used facilities, with the development of cloud computing, IoT and mobile networking, the scale of the Internet is growing rapidly. Due to the poor flexibility, complex controllability and low utilization rate, the traditional TCP/IP network architecture has been unable to meet the needs of rapid development of Internet, companies and research institutions in various countries have already begun to study the next generation of the Internet.In this context, software-defined network (SDN) emerges as a new network deployment architecture, its main feature is the control plane and the data plane of network are separated. The SDN control plane control the overall network resources, the controller is responsible for network topology collection, route calculation, traffic management and other functions, and the data plane only retains the function of transmitting data. To achieve control of the entire network, the controller communicates with the switch through OpenFlow protocol. Currently the majority of SDN networks are based on single centralized controller for it’s easy to deploy the network, but in large-scale network environment, the limited resources and processing power of a single controller will result in network scalability problems, so the job of this article focus on designing a control plane architecture which can solve the scalability problem of SDN.This paper describes the architecture and features of SDN and OpenFlow technology related to controllers, switches and OpenFlow protocol at first. Then this paper uses some examples to explain the main three kinds of solutions for SDN scalability problems. Combining with the idea of topology aggregation, this paper presents a hierarchical control plane architecture, which deploys multi controllers as a tree in its control plane.The architecture abstracts large and complex network into some hierachical small scale network, by limiting the size of network, it reduces the computational complexity of the control plane, so as to solve SDN network scalability issues. Finally, through recoding the open-source controller Ryu which can supports hierarchical control plane architecture and using network simulation platform, the experiments verify the feasibility and the rationality of the architecture. |
