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<DIV><SPAN class=704210410-06022007><FONT face=Arial size=2>Hey
Guys,</FONT></SPAN></DIV>
<DIV><SPAN class=704210410-06022007><FONT face=Arial
size=2></FONT></SPAN> </DIV>
<DIV><SPAN class=704210410-06022007><FONT face=Arial size=2>Is it mandatory for
SIP servers to generate to UA 180 Ringing to inform them that the called party
is now ringing ?</FONT></SPAN></DIV>
<DIV><SPAN class=704210410-06022007><FONT face=Arial
size=2></FONT></SPAN> </DIV>
<DIV><SPAN class=704210410-06022007><FONT face=Arial size=2>The reason i'm
asking is because I am seeing strange results using different
UAs.</FONT></SPAN></DIV>
<DIV><SPAN class=704210410-06022007><FONT face=Arial
size=2></FONT></SPAN> </DIV>
<DIV><SPAN class=704210410-06022007><FONT face=Arial size=2>Using SIP
clients to call out , in</FONT></SPAN><SPAN class=704210410-06022007><FONT
face=Arial size=2>stead of seeing 180 Ringing , i see 183 session progress even
before call was picked up.</FONT></SPAN></DIV>
<DIV><SPAN class=704210410-06022007><FONT face=Arial
size=2></FONT></SPAN> </DIV>
<DIV><SPAN class=704210410-06022007><FONT face=Arial size=2>On some sip client ,
ring back can be heard.</FONT></SPAN></DIV>
<DIV><SPAN class=704210410-06022007><FONT face=Arial size=2>On some others ,
ring back cannot be heard.</FONT></SPAN></DIV>
<DIV><SPAN class=704210410-06022007><FONT face=Arial
size=2></FONT></SPAN> </DIV>
<DIV><SPAN class=704210410-06022007><FONT face=Arial size=2>Is there any reason
to suspect that these UAs needs to receive 180 Ringing before generating any
ringback ?</FONT></SPAN></DIV>
<DIV><SPAN class=704210410-06022007><FONT face=Arial
size=2></FONT></SPAN> </DIV>
<DIV><SPAN class=704210410-06022007><FONT face=Arial
size=2>Regards,</FONT></SPAN></DIV>
<DIV><SPAN class=704210410-06022007><FONT face=Arial
size=2>Sam</FONT></SPAN></DIV></BODY></HTML>