Which API technology with SDN architecture is used to communicate with a controller and network devices such as routers and switches?

REST APIs are a *type* of API that can be used, but 'southbound APIs' specifically defines the role and direction of communication in SDN for controller-to-device interaction.

Northbound APIs are used for communication between the SDN controller and higher-level applications or orchestration systems, not directly with the network devices themselves.

In an SDN architecture, southbound APIs are the interfaces specifically used by the SDN controller to communicate with and program the data plane of underlying network devices like routers and switches. These APIs translate the controller's high-level instructions into device-specific commands to manage traffic flow.

'Unprotected APIs' is not a standard category of API technology in SDN and implies a lack of security, which is generally not a design goal.