What Is Software Defined Networking

Software Defined Networking (SDN) is an emerging network architecture where network control is decoupled from forwarding and is directly programmable. SDN is essentially moving from distributed configuration to controlling the network from a logically centralized high level program i.e. Controller.

conventional switching architecture vs sdn switching architecture

  • Controls the entire network by governing all the flows on the network elements. Intended to make NEs dumb (having only Data Plane) by moving the logic to Controller Layer. So controller computes the logic of how traffic will be forwarded.
  • Thus, Data Plane consists of programmable devices and Control Plane consists of Controller & Apps.
  • SDN requires some method for the control plane to communicate with the data plane. One such mechanism is OpenFlow.


  • Networks that are configured/reconfigured via software tools.
  • Networks defined according to the needs of software/applications using them.
  • Can support multi-layer provisioning.
  • The term “SDN” was coined in year 2009.

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