ovn 有两个运行进程，以下为作用。
The Daemons
ovn-northd
- Converts from the high-level northbound DB to the run-time southbound DB.
从高层北向数据库转换到南向运行数据库
Generates logical flows based on high-level configuration.
- 基于高层（抽象）配置生成逻辑流表
ovn-controller
- Register Chassis and VIFS to southbound DB
- 在北向数据库注册 Chassis （底盘 ，ovn新增的概念）以及 VIFS ( Virtual network interfaces ) 信息
- Converts logical flows into physical flows ( ie,vif UUIDs to openFlow Ports )
- 转换逻辑流表为物理流表（ 如转换虚拟网络接口为 openFlow 接口 ）
- Pushes physical configuration to local OVS instance through OVSDB and OpenFlow
- 通过ovsdb与OpenFlow协议往本地ovs进程推送物理配置