If the Operating System does not mark it, you can mark it with rules on the controller, by using an ACL to identify the direction and UDP port and having it mark the traffic using TOS or DSCP. Below is an example of an ACL you can add to a user role to do this: (you will have to use the magnify function in your browser to see the screenshot below).
This marking will take place when it leaves the controller and goes to your infrastructure, since the client does not do any marking itself.