Ronny Lam


The Definition of SDN

Yesterday I read a great post by Ivan Pepelnjak:

As I’ve been thinking about controllers, central visibility and network device programmability, it struck me: we already had SDN in 1993 … and didn’t know it.

This resulted in a couple of tweets back and forth in which I also claimed that the definition of SDN is still unclear and that every vendor is skewing it to their own use. Today, SDNCentral published a presentation on Slideshare about the primer of SDN. It contains a definition which uses the same words as Ivan is using:


  1. Separates the network’s control and forwarding planes;
  2. provides a centralized view of the overall network;
  3. utilizes programmatic application interfaces (API’s);
  4. enables efficient orchestration and automation of network services.

I expect these to be AND operators and not OR, but there are still vendors that miss one or two items.

I like that the presentation is including some of the predecessors of SDN, including Ivan’s example. Tomorrow I’ll write about the status of SDN.