[SR-Users] Issue with duplicite SIP messages in traffic loop

[Michal Popovič]

Hello,

I am trying to configure kamailio to use external antifraud protection using so called "traffic loop" when call is forwarded to external SIP proxy that would response even with same INVITE back or with error message if number is fraud.

schema: PBX -> kamailio -> traffic loop -> kamailio -> carrier

Kamailio in second and fourth step is the same.

Issue is that if kamailio receives same INVITE back to I would like to forward to next carrier it is possible, but kamailio struggles with transaction handling.

If ACK message come from PBX, kamailio will correctly forward it to traffic loop but when it comes back, function t_check_trans is failed and I cant relay it. Only workaround is to use send() message, but that causes deny of BYE message from carrier.

My question is following:
Is it possible to register two different transactions states for same message? If yes how? If no, would it help to send and receive messages on another network port or not?

Thank you,
Michal