Hi i'm enable to find the number of units required for the license of the cisco SIP phone 3911!! i used this link but no way the 3911 was listed below.
The 3911 rquires 2 DLU's :)
Q. Is a station user license required?
A. Yes, the Cisco Unified SIP Phone 3911 requires two (2) Unified Communications Manager Device License Units.
From this good doc;
Hope this helps!