I've been trying to understand the difference between an NOS and an SDN Controller, because in many sources, this term is used interchangeably. For example: https://arxiv.org/pdf/1406.0440.pdf
But then I go searching for OpenFlow enabled switches and I find that they are running a "Network Operating System," such as PicOS or Cumulus Linux and that they are also compatible with SDN Controllers such as Ryu. This leads me to believe that these are two separate designations. The NOS being housed on the forwarding device's hardware in the data plane and the SDN Controller being housed on a separate, commodity hardware platform with an ethernet connection.
Were these once an interchangeable term but has since become two separate things? Or do PicOS and Ryu do essentially the same thing?
Best Answer
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The terms you mention, like a lot of networking terms, are often defined by the system manufacturers, and they are free to have them mean whatever they want in order to sell their products. In other words, the definitions are not precise and can change over time. Different manufacturers can use the same term differently. This is especially true of new, developing technologies like SDN.