A controller communicates with the data plane by using which type of API, such as NETCONF, OpenFlow, OpFlex, or OnePK?

A controller communicates with the data plane by using which type of API, such as NETCONF, OpenFlow, OpFlex, or OnePK?

• A. Northbound API
• B. Eastbound API
• C. Southbound API
• D. Westbound API

Answer: (C)

In software-defined networking, the controller talks to the actual forwarding devices (the data plane) using southbound APIs. These interfaces carry the configuration, rules, and state from the controller down to the switches and routers. The examples given—NETCONF, OpenFlow, OpFlex, OnePK—are all ways the controller communicates with data-plane devices, which is why they’re described as southbound protocols. Northbound APIs, by contrast, are for apps and services to request behavior or information from the controller, not to configure the data plane. Eastbound and Westbound terms are used for communication between controllers in distributed setups or for cross-domain coordination, not for linking the controller to the data plane. So, the interface that handles the controller-to-data-plane communication is the southbound API.

In software-defined networking, the controller talks to the actual forwarding devices (the data plane) using southbound APIs. These interfaces carry the configuration, rules, and state from the controller down to the switches and routers. The examples given—NETCONF, OpenFlow, OpFlex, OnePK—are all ways the controller communicates with data-plane devices, which is why they’re described as southbound protocols.

Northbound APIs, by contrast, are for apps and services to request behavior or information from the controller, not to configure the data plane. Eastbound and Westbound terms are used for communication between controllers in distributed setups or for cross-domain coordination, not for linking the controller to the data plane.

So, the interface that handles the controller-to-data-plane communication is the southbound API.