The first question most readers of an O’Reilly book might ask is about the choice of the cover animal. In this case, “why a duck?” Well, for the record, our first choice was a unicorn decked out in glitter and a rainbow sash.

That response always gets a laugh (we are sure you just giggled a little), but it also brings to the surface a common perception of software-defined networks among many experienced network professionals. Although we think there is some truth to this perception, there is certainly more meat than myth to this unicorn.

So, starting over, the better answer to that first question is that the movement of a duck^[1] is not just what one sees on the water; most of the action is under the water, which you can’t easily see. Under the waterline, some very muscular feet are paddling away to move that duck along. In many ways, this is analogous to the progress of software-defined networks.

The surface view of SDN might lead the casual observer to conclude a few things. First, defining what SDN is, or might be, is something many organizations are frantically trying to do in order to resuscitate their business plans or revive their standards-developing organizations (SDOs). Second, that SDN is all about the active rebranding of existing products to be this mythical thing that they are not. Many have claimed that products they built four or five years ago were the origins ...