What purpose does a northbound API serve in a controller-based networking architecture?

A northbound API (Application Programming Interface) in a controller-based networking architecture allows applications to communicate with the network controller. This enables applications to request network services, provision resources, and gain network visibility, effectively programming the network from a higher level. This abstraction allows developers to integrate network services into their applications without needing to understand the underlying network hardware specifics. Reporting device errors to a controller and generating statistics for network hardware and traffic are functions that might be handled by southbound APIs or management protocols, not northbound APIs. Communicating between the controller and the physical network hardware is the primary role of a southbound API, which translates controller commands into device-specific instructions.