Which statement describes the role of a northbound API in SDN?

Which statement describes the role of a northbound API in SDN?

• A. They provide a programmatic interface for applications to interact with the controller
• B. They describe data-plane forwarding rules
• C. They are used to configure hardware directly
• D. They manage IP addressing on devices

Answer: (A)

Northbound APIs in SDN are the bridge between applications and the network controller. They provide a programmatic interface that lets applications express what they want the network to do—provisioning paths, applying policies, or enforcing quality of service—without needing to know how switches are configured. The controller takes these intents and translates them into concrete, low-level rules on the data plane via its southbound interfaces. This separation unlocks automation and portability, letting the same controller support different applications and hardware. Describing data-plane forwarding rules belongs to the controller’s view of the network and how switches are programmed, not to the app-facing API. Direct hardware configuration and IP addressing on devices are also lower-level management tasks, not what the northbound API exposes to applications.

Northbound APIs in SDN are the bridge between applications and the network controller. They provide a programmatic interface that lets applications express what they want the network to do—provisioning paths, applying policies, or enforcing quality of service—without needing to know how switches are configured. The controller takes these intents and translates them into concrete, low-level rules on the data plane via its southbound interfaces. This separation unlocks automation and portability, letting the same controller support different applications and hardware. Describing data-plane forwarding rules belongs to the controller’s view of the network and how switches are programmed, not to the app-facing API. Direct hardware configuration and IP addressing on devices are also lower-level management tasks, not what the northbound API exposes to applications.