Northbound interface/Southbound interface definition
A northbound interface means an interface that lets a specific component communicate with a higher-level component in the same network. A southbound interface is the opposite — it enables a specific component to communicate with a lower-level component.
Real northbound interface/Southbound interface examples
In software-defined networking, the southbound interface is the OpenFlow protocol specification, which allows communication between the SDN controller and the network nodes.
The northbound interface is protocol-supported communication between the controller and applications or higher-layer control programs.
