Hi Karl,
The enterprise parameter you are looking at is for call signalling.The default value is set as CS3 and I would leave it be CS3. This is for H323, SIP, MGCP, SCCP etc. all call signalling.
If you go to:
System >Service Parameter> Clusterwide Parameters (System - QOS)
It will show you the dscp values for audio calls - which is ef by default.
So I dont think you need to change anything in CUCM. As CUCM is already by default marking audio as ef and signalling as CS3.
Please let us know if you have any more questions.
Terry
Edit: Regards to your second question, there is no limitation on any phone model not supporting dscp marking ef.
Message was edited by: Terry Cheema