What role do commodity (off-the-shelf) switches play in a controller-based network?

In a controller-based network, commodity (off-the-shelf) switches primarily perform the data plane function of forwarding packets. They receive instructions from a centralized controller on how to handle traffic, but they don't make independent decisions about policies or routing. The controller is responsible for setting packet-handling policies and making routing decisions, acting as the network's brain. Providing a central view of the deployed network is also a function of the controller, which gathers information from all connected devices. Therefore, the switches execute the forwarding instructions provided by the controller.