Software Defined Networks

In previous chapters we have seen why SDN is necessary and what preceded the actual advent of SDN in the research and industrial communities. In this chapter we provide an overview of how SDN actually works, including discussion of the basic components of a Software Defined Networking system, their roles, and how they interact with one another. In the first part of this chapter we focus on the methods used by Open SDN. We also examine how some alternate forms of SDN work. As SDN has gained momentum, some networking vendors have responded with alternate definitions of SDN, which better align with their own product offerings. Some of these methods of implementing SDN-like solutions are new (but some are not) and are innovative in their approach. We group the most important of these alternate SDN implementations in two categories: SDN via existing APIs and SDN via hypervisor-based overlay networks, which we discuss separately in the latter half of this chapter.