Hello Vladimir,
Your topology is correct. Your "Controller" host can be anywhere and the OpenFlow communications between the OVS switch and the Controller will take place over the control interfaces. That is why you will need to define the routable IP address of the controller for the OVS switch ($ sudo ovs-vsctl set-controller br0 tcp:<controller_ip>:6633). So, no change is required to the topology!
I would also like to point out that the POX tutorial is no longer being maintained, as noted in the introduction. If you are interested in trying out OpenFlow you can try the experiment suggest in the introduction that uses the FloodLight Controller:
http://groups.geni.net/geni/wiki/GENIExperimenter/Tutorials/OpenFlowOVS-Floodlight Also available is a version of this experiment that uses the Ryu controller.
http://groups.geni.net/geni/wiki/GENIExperimenter/Tutorials/OpenFlowRyuLuisa