To mitigate the potential scalability issues of an OpenFlow-based control plane, a seamless OpenFlow and Path Computation Element (PCE) integrated control plane is proposed, by means of an architecture in which the path computation function is formally decoupled from the controller so the controller can off-load the task to one or more dedicated PCEs using an open and standard interface and protocol, and where the PCE obtains its topology database by means of a dedicated dynamic topology server, which is accessed by the PCE on a per-request basis. The overall feasibility and performance metrics of this integrated control plane are experimentally verified and quantitatively evaluated on a real IP over translucent Wavelength Switched Optical Network (WSON) testbed.