Hello,
If your switch´s are with Qos Feature activate, you need include command for trusted marking originated of application.
If Qos feature not active in your switch´s the command is not necessary.
The phisical phones mark the packets with DSCP EF. CIPC also mark packets with DSCP EF, but only the user is running the application with privilege admin.
For workaround this problem you can created a police of Qos in windows local machine or default domain police.
