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.