ONF just released OpenFlow logo with trademark symbol on it. https://www.opennetworking.org/about/onf-overview
enter image description here

Anyone notice that I explained this over a year ago, yet my answer remains downvoted to near extinction while shallow, yet appreciated, attempts at an answer to "What is SDN" have upvotes.

Also that the term Openflow predates the term SDN in contrast to the harsh critical statement of a leading contributor here? (probably now deleted)

This and ever SE community should be about voting on real world answers to legitimate questions, not about voting based on like/dislike of personality. I would encourage the moderators here to be inviting and supportive of criticism when it is constructive, and to ward off group think, offensive comments, and mob mentality. Aforementioned bahavior devalues the SE as it produces garbage results.

Thanks for listening and we can all learn networking a bit more from one another. Lastly, at this point, I think I am due a t-shirt, or some Colorado Kush by the SE company.

  • "If No OpenFlow™, No SDN," is like saying, "If no HSRP, no FHRP," because HSRP predates the term FHRP, despite the fact that VRRP came along later.
    – Ron Maupin Mod
    Sep 27, 2016 at 21:27
  • I rewrote my answer. OpenFlow and SDN are married; even if a common law marriage, It's true. Oct 2, 2016 at 18:52

1 Answer 1


Again, you are tying different pieces of information together as if they are all one and the same. Let's clarify some terms:

  • SDN - is a concept, a design principle, or as the ONF describes it on their site, "an emerging network architecture"
  • OpenFlow - a standard designed based on SDN concepts, like many things technical, it originally was developed in an academic environment but now manged by the ONF (Open Networking Foundation)
  • ONF - an organization that promotes and provides open standards for SDN, specifically OpenFlow which they have tradmarked.

SDN began as a concept in an academic environment. OpenFlow was the first successful implementation of an open standard based on the concept. Without the concept in the first place, there would be no standard or implementation.

ONF, which has now trademarked OpenFlow, did not exist until 2011, which is at least two years later than published references to SDN.

Despite all this, you keep maintaining that OpenFlow and SDN are synonymous and can't be separated. In your words:

SDN, software defined networking, appears to be a term owned (almost trademarked) by the the Open Networking Foundation. Note Goldman Sachs sits on the ONF board [source wikipedia], go figure. So, though not officially trademarked, SDN is reserved for use by strict adherents to the ONF's OpenFlow protocol. Note that Cisco has created a richer superset Implementation of OpenFlow called onepk/opflex/aci (pick one). In short, if it ain't running openflow, it ain't SDN (technically).

This one paragraph is full of technical inaccuracies. SDN is not "reserved for use by strict adherents to the ONF's OpenFlow protocol"; it is used by other companies/solutions freely and no one has to pay royalties/license fees to use the term SDN (i.e. it is not trademarked in any way). Neither OpenFlow nor the ONF ever make the claim that they "own" the term SDN or that without OpenFlow it isn't SDN. Since you won't listen whenever I try to say it (and I admit I may not have been as clear as I could, but the typed word is often imperfect), let's check to see what does the ONF have to say about this? From their FAQ:

Q: Can I build an SDN without using the OpenFlow® Standard?
A: You could, but you probably wouldn’t want to. Proprietary alternatives
to the OpenFlow® standard lock you into vendor-defined solutions and 
pricing. The OpenFlow® Standard is the only standard protocol that provides 
communication between the control and forwarding functions; it is a vital 
element of an open SDN architecture.

In their own words, you can have SDN without OpenFlow. They just don't think it's a good idea, especially since most of those are proprietary and one of the major purposes of their organization is the promotion of open SDN standards.

Q: What’s the difference between SDN and the OpenFlow® Standard?
A: The OpenFlow® standard is a foundational element for SDN. SDN is an 
emerging network architecture where network control is decoupled from 
forwarding and is directly programmable. The OpenFlow® Standard is the first 
standard communications interface defined between the control and forwarding 
layers of a software-defined network architecture.

Notice this part of the answer: "OpenFlow Standard is the first standard communications interface" (emphasis mine). This implies that they expect there will be others, again alluding to the fact that SDN is not directly tied to OpenFlow.

You will likely focus on the single statement again rather than the entire context of this second answer with regard to "OpenFlow® standard is a foundational element for SDN" (your quote: "If something is the foundational element, is it a key element, meaning can that thing, SDN in this case, cannot exist without the element in question."). Since this is a metaphor based in construction of buildings, let me make it clear that you can have a number of different types of foundations, based on different materials, but everything built on top of that foundation is still considered a building. Just because OpenFlow is one particular "foundation" does not mean that no other foundation can exist, nor that those other foundations cannot provide a solution which is SDN.

  • Appreciate the answer. Pls see my updated answer networkengineering.stackexchange.com/questions/19321/…. OpenFlow and SDN are married. It's true. I think the bigger point is SDN vs OpenStack. In other words, network automation vs the-whole-thing automation. Oct 2, 2016 at 18:51
  • See, you miss the whole point. OpenFlow and SDN are not married. Not even in the view of the ONF. If you are looking for a relationship, OpenFlow is a child of SDN, but SDN has and will continue to have more children.
    – YLearn
    Oct 3, 2016 at 18:05
  • OpenFlow and SDN are two different points. You could say that OpenFlow is a flavor of SDN. But Software Defined Networking is a rather broad term, whose definition is kind of hard to exactly pinpoint. It however includes OpenFlow (being quite an early "implementation" of SDN), but certainly they're not tied together the way you describe. SDN can exist without OpenFlow. Just read any SDN journal, have a look on conference proceedings of major SDN conferences. Many people tried to explain that they have other opinions, yet you keep saying that your opinion is the one and only true one.
    – Daniel
    Oct 27, 2016 at 2:46
  • BTW: OpenStack is software for managing and controlling public and private clouds. Certainly OpenStack makes use of some SDN technologies (depends on the actual implementation) and integrates them into an automation software controlling more than the network only. But still - you don't have to use OpenFlow here, and for sure we can agree that SDN technologies are used in OpenStack to control and manage the network part?
    – Daniel
    Oct 27, 2016 at 2:50

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .