Thanks for your support, I am trying to do this but to be honest I don't know how to arm the failure route for this case of "fr_inv_timer". When I received reply 183 I use t_set_fr() function to set the new value for "fr_inv_timer", do far so good, but I never received failure_route[0] when Kamailio terminate the call sending 408, even calling like this: t_on_failure("0"); t_relay(); I can't find on documentation how to do this. Thanks a lot