SDN North-bound and South-bound APIs and Interfaces

There are two essential components of an SDN controller: the northbound interface and the southbound interface. It uses the northbound interface to connect with the application you use to configure the controller. It uses the southbound interface to communicate with network devices and implement the configurations made through the controller.

To determine where the NBI and SBI reside, you first need to consider the SDN controller itself. The SDN controller is a device or software running on a server in the same network. It works as a bridge between administrators and network devices. It takes instructions from administrators and implements them on network devices. To communicate with administrators and network devices, it uses APIs. An API (Application Programming Interface) is a set of application logic functions that perform different actions. In SDN networking, APIs move information from the application administrators use to manage changes to the controller, and then move data from the controller to the network devices.

An SDN uses two APIs: the northbound API and the southbound API. It uses the northbound API to move data between the administrators' application and the controller. It uses the southbound API to move data between the controller and the network devices.

An API uses a client/server architecture in which each execution needs a client and a server. The client receives the data. The server sends the data. With the northbound API, the server is the application that the administrator uses to configure settings on the controller, and the client is the controller itself. With the southbound API, the server acts as the controller, while the client is the network device that receives configuration from the controller.

The Northbound Interface

A controller's northbound interface (NBI) allows other programs to access the controller. Administrators can use any supported program to access a controller's functions through its northbound interface. The program can pull information from the controller using its APIs. The controller's northbound interface allows the program to utilize its capabilities to program flows into network devices via the southbound interface.

Southbound Interfaces

SDN uses the South Bound Interface (SBI) to communicate with network devices and implement the configuration it receives from the administrator's application. Different SDN controllers use different southbound APIs. For example, OpenDaylight, a popular open-source SDN Controller, uses a protocol called OpenFlow to communicate with network devices. On the other hand, Meraki currently uses a proprietary solution since it manages everything itself.

Conclusion

Northbound and southbound interfaces define the structure of the SDN controller. The northbound interface serves as the bridge between the controller and the application you use to manage and configure network settings effectively. Conversely, the southbound interface facilitates communication between the controller and the network devices, ensuring that configurations are implemented seamlessly.

APIs play a crucial role in this architecture, serving as the channels through which data flows, both from the applications to the controller and from the controller to the network devices. This clear separation of functions between the northbound and southbound interfaces allows for a more agile and flexible network management environment, accommodating various applications and network devices through standardized and proprietary protocols. Overall, understanding these components is vital for optimizing and enhancing network operations in an SDN framework.