关键词: 软件定义网络, SDN控制器, 网络架构

Abstract: The network architecture has been used for nearly 30 years. In order to make the whole network run smoothly, switches/routers have to run within more than 6000 protocols, which means if one network point increases a protocol the other points also have to make changes. SDN（Software Defined Network） makes the network programmable, so that it enables the network to be more flexible to fit needs of network users. In the SDN architecture, the control and data planes are decoupled, network intelligence and state are logically centralized, and the underlying network infrastructure is abstracted from the applications. As a result, enterprises and carriers gain unprecedented programmability, automation, and network control, enabling them to build highly scalable flexible networks that readily adapt to changing business needs. SDN controller plays a very important role in SDN because not only does it communicate with the underlying devices but also provides APIs for the application layer. This paper analyzes the background and principle of SDN as well as its development at first; then it does some researches on an open source project——Floodlight; at last this paper summarizes and analyses the features of SDN controller.

Key words: Software Defined Network（SDN）, SDN controller, network architecture