Which plane is centralized by an SDN controller?

The management plane is concerned with network monitoring, configuration, and troubleshooting; while an SDN controller aids in management, it primarily centralizes the control plane.

The data plane (or forwarding plane) is where actual network traffic is forwarded based on rules from the control plane, and it remains distributed across network devices, not centralized by the controller.

The term 'services-plane' is not a standard network plane in the context of SDN architecture.

An SDN controller centralizes the control plane, which is responsible for making decisions about how traffic flows through the network and then pushing those rules to the data plane devices.