You can read this
http://www.sipindex.com/viewtopic.php?f=6&t=15791
this is response of intelligent xlite:
#
U 195.167.152.55:5060 -> 89.243.144.156:10267
BYE sip:andres.moya@89.243.144.156:10267 SIP/2.0.
Via: SIP/2.0/UDP 195.167.152.55;branch=z9hG4bKf2f.97c1e015.0.
Via: SIP/2.0/UDP 192.168.17.100:22364;received=195.167.152.253;branch=z9hG4bK-d8754z-57bea456af8fa652-1---d8754z-;rport=61268.
Max-Forwards: 69.
Contact: <sip:mangust@195.167.152.253:61268>.
To: <sip:andres.moya@riki.ru>;tag=g09otf1f62q7dntff2vil432.
From: "Andres"<sip:mangust@riki.ru>;tag=09415166.
Call-ID: OTliNWZhZDA4OWU1ODRiYTg5ZDIwYzc4N2U4YTdiYTM..
CSeq: 2 BYE.
User-Agent: X-Lite Beta release 4.0 Beta 2 stamp 55091.
Reason: SIP;description="RTP or RTCP inactivity".
Content-Length: 0.
.
If someone got solved, call me on sip:andres.moya@riki.ru