THE NORTHBOUND APIs OF SOFTWARE DEFINED NETWORKS

Most traditional network architectures have their data plane and control plane put together, that is, they are vertically integrated. To combat the disadvantages of these kind of architectures, the concept of programmable networks was introduced, and has gained a lot of momentum since then. These are known as Software Defined Networks (SDN). The usual physical boundaries in a network like switches and routers are broken in SDN architecture using Application Programming Interfaces (API). The API that resides in between the controller and the application layer in SDN is known as the Northbound API. Northbound API presents a network abstraction interface to the applications and the management systems at the top of the SDN stack, and is hence considered to be the most important component of SDN Architecture. Due to its dynamic nature and the many developments occurring in it, the standardization of Northbound API has been a topic of discussion. This paper gives a brief overview of SDN, with a focus on the Northbound API. We survey the different kinds of Northbound API that currently exist, and then present the various opinions that exist on their standardization.