[Freeswitch-users] Probably obvious but not to me - sofia hangup

[general at bestoronto.com]

Hi, I am on freeswitch / centOS: Linux pbx 2.6.18-194.11.3.el5.centos.plus #1 
SMP
It is a fairly straight out of the box freeswitch config, I am not so good 
with XML yet.
Issue is the line to my single SIP phone will drop after about 8 minutes, no 
matter if talking or not.
What might be the cause of this? Seems like a timeout or lack of ACK 
somewhere?
Thanks for the help....
Mark B