Hello, I might not fully understand the scenario, but usually you just do record-routing on the proxy and then the ACK will be routed as in-dialog request. So, no transaction handling should be involved in the "end to end" ACK case. Cheers, Henning -- Henning Westerholt - https://skalatan.de/blog/ Kamailio services - https://gilawa.com -----Original Message----- From: sr-users <sr-users-bounces(a)lists.kamailio.org> On Behalf Of Michal Popovic Sent: Wednesday, October 12, 2022 1:24 PM To: Kamailio (SER) - Users Mailing List <sr-users(a)lists.kamailio.org> Subject: [SR-Users] Issue with duplicite SIP messages in traffic loop 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 __________________________________________________________ Kamailio - Users Mailing List - Non Commercial Discussions sr-users(a)lists.kamailio.org Important: keep the mailing list in the recipients, do not reply only to the sender! Edit mailing list options or unsubscribe: https://lists.kamailio.org/cgi-bin/mailman/listinfo/sr-users