Is SDN a concept, or a concrete architectural construct? Does it really matter?

A question – specific to F5 technology – was raised during the panel session I moderated at Gartner DC 2012 that for me, at least, raised an interesting question. Well, actually it wasn't just that question, but rather the question was the icing on the cake after hearing commentary from enterprise IT attendees on the subject of SDN.

Yes, there's already a spate of SDN-washing, similar to cloud-washing, that's going on in the market. While ONF certainly laid out a set of characteristics defining SDN, those characteristics are not a concrete list of requirements. It's not, after all, an RFC, with an easy to evaluate list of "MUST NOT, MUST, SHOULD NOT, and SHOULD" requirements. As Captain Barbosa said, "…the code is more what you'd call "guidelines" than actual rule."

The questions and commentary raised by IT attendees at the conference can be summed up in two questions:

1. What is SDN?

2. What problem is it trying to solve?

This is really the heart of the debate for IT. Adoption is not going to occur (one person out of the 50 attending the session had one guy, in a lab, playing with OpenFlow, for example) until at least the second of these questions can be definitively answered by those selling SDN solutions.

The answer to that question seems to center around a concept – agility. Agility, however, is also one of those broad terms that can mean anything from adaptability to flexibility to extensibility. Any of these concepts – and they are concepts – can be implemented in a variety of ways, some of which may fit the criteria set by ONF for SDN and some that may not. That's what leads to "washing" solutions; criteria using language and terminology that can easily be interpreted in a number of ways.

Let's refresh our memories, shall we?

“In the SDN architecture, the control and data planes are decoupled, network intelligence and state are logically centralized, and the underlying network infrastructure is abstracted from the applications. As a result, enterprises and carriers gain unprecedented programmability, automation, and network control, enabling them to build highly scalable, flexible networks that readily adapt to changing business needs.” [emphasis added]

-- Software-Defined Networking: The New Norm for Networks, ONF