What is a function of a northbound API in an SDN environment?

In a Software-Defined Networking (SDN) architecture, the northbound API (NBI) serves as the critical interface between the SDN controller (control plane) and the applications or orchestration systems (application plane). Its primary function is to abstract the underlying network complexity and provide a programmable interface. This allows automation scripts, orchestration platforms, and other network applications to programmatically request network resources, define policies, and automate network management tasks. Essentially, the NBI is the key enabler for network automation and orchestration services by translating application requirements into actions the controller can execute.

A. This describes a function of the distributed control plane or the interaction between the controller and devices, not the northbound API's role.

B. This describes a capability of the centralized SDN controller itself, whereas the northbound API is the interface used to access this capability.

C. This is a specific network management task. While it could be initiated via an application using the NBI, it is not the fundamental function of the API.

1. Odom

W. (2019). CCNA 200-301 Official Cert Guide

Volume 2. Cisco Press.

Chapter 24

"Introduction to Network Automation

" Section "SDN Northbound and Southbound APIs": This section explicitly states

"The controller’s northbound APIs are used by network applications. These applications might be network automation and orchestration platforms... The application uses the API to give the controller instructions about the goal." This directly supports that the NBI's function is to enable automation and orchestration.

2. Cisco. (2023). Cisco DNA Center Platform Overview. Cisco Systems

Inc.

Section "Northbound APIs": The documentation describes the northbound APIs of Cisco DNA Center (an SDN controller) as providing "rich and easy-to-use REST APIs that allow you to programmatically control your network and integrate with your preferred operational systems." This confirms the role of NBIs in providing programmatic control for automation and orchestration.

3. Kreutz

D.

Ramos

F. M. V.

Veríssimo

P. E.

Rothenberg

C. E.

Azodolmolky

S.

& Uhlig

S. (2015). Software-Defined Networking: A Comprehensive Survey. Proceedings of the IEEE

103(1)

14–76.

Section IV.A

"The Northbound Interface": This peer-reviewed paper states

"The northbound interface is arguably the most important and yet the least specified part of SDN. It opens up the control of the network to third-party applications

enabling innovation... It is the key to deliver the promised flexibility and programmability of SDN." This highlights its role in enabling applications to program the network

which is the foundation of automation. (DOI: https://doi.org/10.1109/JPROC.2014.2371999)