Aastra registration timeout bug

If the Aastra phone registration times out faster than expected and faster than what is set in the 'Line' section, check the Global SIP settings:

Under the 'Advanced Settings' tab, choose Global SIP. In the “Basic SIP Network Settings" section change the value of "Registration Period" to zero (0). With this value set to zero, the phone will use the value under the "Line" section.