SDN: Software Defined Networks

Chapter 4. SDN Controllers

Introduction

The three most resonant concepts of SDN are programmability, the separation of the control and data planes, and the management of ephemeral network state in a centralized control model, regardless of the degree of centralization. Ultimately, these concepts are embodied in an idealized SDN framework, much as we describe in detail later in Chapter 9. The SDN controller is the embodiment of the idealized SDN framework, and in most cases, is a reflection of the framework.

In theory, an SDN controller provides services that can realize a distributed control plane, as well as abet the concepts of ephemeral state management and centralization. In reality, any given instance of a controller will provide a slice or subset of this functionality, as well as its own take on these concepts. In this chapter, we will detail the most popular SDN controller offerings both from commercial vendors, as well as from the open source community. Throughout the chapter, we have included embedded graphics of the idealized controller/framework that was just mentioned as a means to compare and contrast the various implementations of controllers. We have also included text that compares the controller type in the text to that ideal vision of a controller.

Note

We would like to note that while it was our intention to be thorough in describing the most popular controllers, we likely missed a few. We also have detailed some commercial controller offerings, but likely missed ...