Hello, the ACK doesn't get through the branch_route block because it is forwarded in stateless mode. The ACK doesn't have a reply, therefore is not transaction state to be kept for it. You have to apply all the rules you want for the ACK inside the request_route logic. If there is a retransmission of the ACK, again it is not detected, so it will just run again through the same rules in request_route. This is of course for the ACK following the 200ok. Cheers, Daniel June 25, 2019 1:42 PM, "Bandiera, Enrico" < enrico.bandiera(a)cloud.timenet.it &lt;%22Bandiera,%20Enrico%22%20%3Cenrico.bandiera(a)cloud.timenet.it%3E&gt;&gt; wrote: Hi, I'm encountering an issue when relaying late offer ACKs, before relaying I set the branch_route with t_on_branch() but kamailio never enters that route after calling t_relay I'm keeping the rtpengine module calls inside branch_routes to avoid issues when re-routing in failure routes I suppose it's something related to ACK packets but I'm not sure what the issue is. Any hints? Thanks, Enrico. -- Daniel-Constantin Mierla www.kamailio.org -- www.asipto.com _______________________________________________ Kamailio (SER) - Users Mailing List sr-users(a)lists.kamailio.org https://lists.kamailio.org/cgi-bin/mailman/listinfo/sr-users