Aastra 9000i Series Administrator's Manual page 642

Aastra Web UI
4 Click on Advanced Settings->Global SIP->Advanced SIP Settings.
5 In the "Advanced SIP Settings" section, in the "As-Feature-Event Subscription Period" field, enter
the amount of time, in seconds, that the phone waits after sending a SUBSCRIBE, to receive a
NOTIFY response from the server side.
Default is 3600. Valid values are
6 Click
41-001343-01 Rev 02, Release 3.2.2
to save your changes.
As-Feature-Event
Subscription
Period
6-21