软件定义联网( SDN)和传统网络的区别在于将传统网络设备的转发层和控制层相分离，网络设备的控制功能都集中到了控制器中，转发功能则完全保留在设备之中。 SDN分为三个层次：数据层、控制层和应用层。北向接口位于应用层和控制层之间，其作用是向上层应用开放网络能力，具备开放性、便捷性、灵活性等特性。针对上层应用对网络能力的定制化需求，提出一种支持QoS服务可定制的北向接口的设计方案，描述了接口的外部形式和内部功能模型并基于该方案实现了一个提供带宽和优先级可定制服务的北向接口。在SDN实验网络中对接口进行了测试，测试结果表明该方案能够达到预期目标。%SDN is different from the traditional network in that it decouples the control layer from the forwarding layer. Control functions are centralized at a controller and the underlying hardware only contains forwarding functions. SDN is composed of three layers:the data layer,control layer and the application layer. The interface between the application layer and the control layer is called Northbound Inter-face (NBI),which opens the network abilities and possesses sufficient openness,convenience,and flexibility. For the customization de-mand of upper application for network capacity,a design plan of the NBI is proposed which supports for customizing QoS services. To provide customization to better meet applications’ needs,a design of northbound interface for customizable QoS services is put forward. A high-level API specification and functional model is described. A bandwidth-and-priority-based QoS service is implemented accord-ing to the specification. A prototype system is built on an SDN test bed,and the result shows that it can achieve the expected goal.
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