In software defined network architecture, what function is removed from network devices and performed by an SDN controller?

In a Software Defined Network (SDN) architecture, the function that is removed from network devices and performed by an SDN controller is the control plane or the network intelligence.

Here are the steps to understand this:

1. Traditional Network Architecture: In traditional network architecture, each network device, like a router or switch, has its own control plane. This means each device makes its own decisions about where to send traffic based on its current view of the network.

2. Separation of Control and Data Plane: SDN architecture separates the network control plane from the data plane. The control plane, which makes decisions about where traffic is sent, is removed from the network devices.

3. SDN Controller: In SDN, this control plane function is performed by the SDN controller. The SDN controller is a central unit that has a holistic view of the network. It makes traffic decisions and pushes rules down to the network devices on the data plane.

4. Network Devices: The network devices in an SDN architecture become simple packet forwarding devices that operate under the instructions sent to them by the SDN controller.

So, in summary, the function that is removed from network devices and performed by an SDN controller in a Software Defined Network architecture is the control plane or network intelligence.