[Kamailio-Users] t_newtran/t_reply vs. sl_send_reply

Hello, sorry if this is a stupid question, but in the openser.cfg that comes with the source, I see the following: if (!lookup("location")) { switch ($retcode) { case -1: case -3: t_newtran(); t_reply("404", "Not Found"); exit; case -2: sl_send_reply("405", "Method Not Allowed"); exit; } } Could you tell me why we use t_newtran/t_reply for cases -1,-3 and sl_send_reply for case -2. I read docs for modules sl and tm but I still don't get it why we shoud created a transaction in one situation and not in the other. Regards, takeshi