UA         Asterisk        OpenSER       MetaSwitch      VoIP2PSTNGateway
> 102 Invite >>
<<<<< Trying  <
               > Invite 102 >>>
               <<<<<<<< 183 Session Progress <
<<<<<< 183 SP <
               <<<<<<<<<<< 200 OK 102 INVITE <
               > ACK >>>>>>>>>>
<< 200 OK 102 <
               > 103 Invite >>>
> 102 ACK >>>>>
<< 102 Invite < ;reinvite rtp stream to Gateway
>> RTP STREAM to VOIP 2 PSTN >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
               <<<<<<<<<<< 200 OK 103 INVITE <
               > 103 ACK >>>>>>
**** Missing Step here between Asterisk and OpenSER/Metaswitch***
> 200 OK 102 >>
<<<<< 102 ACK <