[Freeswitch-users] Where does "Expires:" in a sip trace come from?

This newbie has 60+ hours into this problem and I really needs some expert explanation for 2 items in a "sofia profile external siptrace on": 1. The section that starts with "REGISTER", the line that reads "Expires:". Does the value always reflect what FS has set or is it reflecting the ITSP? I thought it was the expiry-seconds from the gateway definition. 2. Same question for the "SIP/2.0 200 Ok" section, line "Contact:", at the end it reads "expires:". Thanks. Mario