Plane decoupling

Traditional network architecture comprises three distinct planes (control, data, and management), which enable full functionalities:

The main characteristics of SDN are the segregation of the control plane (which determines the way the traffic should be handled) and the data plane (which forwards the traffic based on decisions made by the control plane) based on incoming traffic parameters, such as the MAC address, IP address, and Virtual Local Area Network (VLAN) ID.

In SDN, these policies are determined by the control plane, which is decoupled from the switch (known as the forwarding element) to a logically centralized controller which can physically be distributed and communicated to the forwarding element via a secure link (OpenFlow channel):

In the preceding diagram, the forwarding elements that will operate in SDN environments are designed to handle the data plane. The most predominant forwarding elements are designed to support traditional network architecture and SDN network architecture. Control and management plane functionalities are moved to a high-performance server that serves as the controller.