I have set up SIP trunks with provider.  I am getting one way audio.  When I call out via SIP Trunk the person outside the MITEL can hear me however I can't hear them on mitel also I'm not getting ringback while call is ringing.  I am not using MBG.  My IT Dept is NAT'ing via a Palo Alto firewall.  It seems like it is a maybe a RTP issue.  Just curious could I see one way audio in a SIP Trace, if so what would it look like.  Any help appreciated