QoS: the parts people skip
Marking traffic achieves nothing on its own. The queue is where the work happens.
Writing
Voice
SIP, RTP, QoS and the network underneath a phone call: why audio breaks, how to prove where, and how to design so it does not.
Your call quality problem is not a voice problem
Complaints after a UC rollout arrive pointed at the phone system. The cause is usually a trust boundary, a queue or a routing change three hops away.