Since the introduction of Cisco’s Collaboration Edge environment, I’m seeing more of a requirement to modify the Ring No Answer Duration timer under the Users Line to a timer above 20 seconds. This is because, by the time the signalling routes to the Jabber Mobile Device, the default Ring No Answer Duration timer has a couple of seconds remaining before expiring and forwards the call to an alternate destination, which is voicemail in most cases. I have found between 20 – 24 seconds is a balanced ground between, not having the phone ring too long at the desk and allowing the Jabber Mobile Device enough time for the user to answer the call.

To change the default the Ring No Answer Duration in CUCM, go to the Service Parameters and navigate to ‘Forward No Answer Duration’. Default is 12 seconds. Modify this parameter to 20 seconds.