Yes, retransmissions of initial INVITE from Carrier. Makes perfect sense, I understand now. Thanks Gentlemen! JR Reinvites are in-dialog requests; they would only be sent within the context of an established dialog (2xx response, end-to-end ACK, the whole works). Perhaps what you are referring to is not reinvites but retransmissions of the initial INVITE? If so, have a look at this option: https://kamailio.org/docs/modules/5.2.x/modules/tm.html#tm.p.cancel_b_method in concert with something like this: failure_route[...] { if(t_is_canceled()) exit; # The scenario you're after. if(t_branch_timeout()) { t_reply("503", "Service Unavailable"); exit; } } -- Alex