Another important thing :
that my SIP conversation :
User --------> OpenSER --------> Asterisk
User -INVITE-> OpenSER
OpenSER-INVITE->Asterisk
Asterisk -Trying-> OpenSER
Asterisk -Session progress-> OpenSER
OpenSER -Session progress-> User
Asterisk -service unavailable-> OpenSER
OpenSER-ACK->Asterisk
OpenSER -service unavailable-> User
User -ACK-> OpenSER
My endless t_relay is this ACK user to openser.