Greetings, 

How sould a call duration be calculated?

Let's say the call creation on Kamailio as a proxy has those steps : 

1 - Invite is received

2 - Provisional responses

3 - 200 OK is received

4 - ACK to 200 OK is received

5 - BYE is received 

6 - 200 OK to BYE is received

Should the duration begin to count on step 3 (200-Ok Received) or 4 (ACK received) ?

Should it end on the step 5 or 6?

ACC module tells me that start time for CDR can either be on dialog creation or confirmation - https://www.kamailio.org/docs/modules/5.2.x/modules/acc.html#acc.p.cdr_start_on_confirmed

- What is the dialog creation ? Is it when the INVITE is received ? 

- According to DIALOG module, a confirmed dialog can be "Waiting for ACK" or "Active Call". Which one is used by acc module?  

Best Regards,