I'm a bit confused between Software-Defined Networks and OpenFlow. As far as I know, OpenFlow is just a protocol that manages the communication between the controlling plan and forwarding plan but I don't know where SDN takes place here. Is it the controller itself? How do I distinguish between them and when to say OpenFlow or SDN.

Thank you.

  • 1
    OF is an implementation of SDN. It isn't the only one, btw.
    – Ricky
    Commented Oct 19, 2015 at 20:25
  • Did any answer help you? if so, you should accept the answer so that the question doesn't keep popping up forever, looking for an answer. Alternatively, you could provide and accept your own answer.
    – Ron Maupin
    Commented Aug 12, 2017 at 18:59

3 Answers 3


Openflow is to SDN


OSPF is to Routing

  • Thanks Ron for reply. So Openflow implements what the SDN decides, right?
    – Mike
    Commented Oct 19, 2015 at 16:41
  • More accurately, Openflow is used to communicate between the controller and the devices (switches).
    – Ron Trunk
    Commented Oct 19, 2015 at 16:42
  • Can we always picture SDN as a combination of three planes: Application, controlling, and data planes.
    – Mike
    Commented Oct 19, 2015 at 16:45
  • See if this other question helps you: networkengineering.stackexchange.com/questions/19321/…
    – Ron Trunk
    Commented Oct 19, 2015 at 16:47

Openflow is just the protocol used for communicatuin between the controller and a switch. This is considered the southbound communication. SDN is too vague and over used. There is no direct comparison. However openflow would fall under the SDN umbrella.

If you want to compare openflow, then compare it to a proprietary protocol doing the same function.


SDN is a concept of a network that virtualizes it control plane and allows it to be programmable (Therefore it has the name "Software-Defined"). Whether you look inside of SDN, you'll see a set of protocols and tools for enabling software defined. One of this protocols is the OpenFlow, however you have another protocols that does almost the same stuff (NFV - Network Function Virtualization) and also other tools that are considered as SDN, such as OpenStack.

Practical examples:

  • You can use both SDN or OpenFlow, since you're using the OpenFlow protocol in your research (as an example).

  • You cannot use OpenFlow whether you're dealing with another protocol (e. g. NFV). Nevertheless, you can still use SDN in this case.

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