What type of API is OpenFlow?

OpenFlow is classified as a Protocol API, which specifically refers to its nature as a communication protocol that enables the interaction between the control plane and the data plane in networking devices. It allows for the implementation of software-defined networking (SDN) by defining how network devices should respond to various network traffic patterns.

The protocol facilitates the programming of switches and routers, enabling the control of network behaviors in a more flexible way compared to traditional networking methods. It provides a standardized way for controllers to communicate with the forwarding elements, allowing for dynamic adjustments based on network conditions without direct human intervention.

In contrast, RESTful APIs are based on representational state transfer principles, often used in web application interfaces, whereas Web APIs generally refer to APIs that are available via the internet. Graphical APIs involve visual components and user interfaces, which are not applicable to OpenFlow's primary function in networking. Thus, the classification of OpenFlow as a Protocol API is supported by its specific purpose and operational scope within the realm of network management and control.