Once a call is answered FreeSWITCH sends a 200 OK SIP message to your Kamailio loadbalancer. As per the SIP spec your kamailio box should respond to a 200 OK with an ACK. The FS logs show that it never receives an ACK, and it repeatedly tries sending the 200 OK with no response. After 30 seconds without an ACK FS will assume the call has failed and hangup.

Looking at your Kamailio SIP logs you can see the 200 OKs getting through okay, and no attempt to send an ACK back to FS. I think this indicates an issue with your kamailio.cfg rather than FreeSWITCH.

Sean
www.wirex-precision.co.uk

On Fri, Sep 1, 2017 at 3:40 PM, Микита Нікітенко <nikitanikitenko@gmail.com> wrote:

Hello! I have server at digital ocean with a floating ip address and I have routed sip traffic to this floating ip. At this server installed kamailio which balancing between freeswitch servers. I have a problem that call drops after 32 seconds with error ACK Timeout. Traffic comming throug the kamailio proxy. 

kamailio.cfg - https://pastebin.com/x0CL3TEZ

kamailio sip messages log - https://pastebin.com/wyT3cBbD

freeswitch logs with sip debug - https://pastebin.com/zPysfQkV

I'm struggling for a week and have no idea how to fix it. 

Thank you very much.

Mykyta Nikitenko