In an SDN architecture, what function does a northbound API provide?

A northbound API in an SDN architecture allows applications and orchestration systems to programmatically interact with and control the network. It provides an abstract view of the network services managed by the SDN controller, enabling higher-level applications to request and configure network resources without needing to understand the underlying infrastructure details. This abstraction simplifies network management and automation. "Access to managed network resources from a centralized node" is too general and doesn't specifically define the API's role in programmatic control. "Communication between SDN controllers and physical or virtual forwarding devices" describes a southbound API's function, which translates controller instructions into device-specific commands. "Controlled access to switches by automated security applications" describes a potential use case of an SDN, but not the fundamental function of a northbound API itself.