<font size=2 face="sans-serif">Dear Gnana,</font>
<br><font size=2 face="sans-serif">let me answer you inline...<br>
</font>
<ul>
<li><font size=3 color=blue>What is the purpose of rport and received parameter
in sip via header? <br>
</font><font size=2 face="sans-serif">The purpose of the rport parameter
is to convey the fact that your SIP UAC (VoIP-Phone) isn't able to detect
its external signalling port (e.g. because it is behind a Firewall or NAT/PAT)
and consequently the port information in the Contact header mitght be wrong.<br>
The received parameter is populated by the UAS (SIP Server / VoIP platform).
The UAS puts in the received parameter the source port from the IP packet
which was sent from the UAC, that carried your SIP message.<br>
</font>
<li><font size=3 color=blue>Will it be needed if sip client is behind NAT
router? <br>
</font><font size=2 face="sans-serif">It is needed in cases where the VoIP
phone isn't able to determine its communication parameters (IP/Port in
Contact), normally it doesn't harm, when rport is sent although the Contact
header carries correct information.<br>
</font>
<li><font size=3 color=blue>If so, how router can process this sip header
as router only handle the IP header but cannot application layer header?<br>
</font><font size=2 face="sans-serif">Your local router isn't responsible
to populate the received parameter, since (as you already correctly stated)
this is an application layer header. It is the responsibility of the SIP
platfrom.</font></ul>
<br><font size=2 face="sans-serif">Ideally the SIP UAC / VoIP phone
learnse its external port and re-register and/or sends it subsequent SIP
Messages with the updated external port.</font>
<br><font size=2 face="sans-serif">If you didn't stumble across it yet:</font>
<br>
<br><a href=https://www.ietf.org/rfc/rfc3581.txt><font size=2 color=blue face="sans-serif">https://www.ietf.org/rfc/rfc3581.txt</font></a>
<br>
<br><font size=2 face="sans-serif">Greetings</font>
<br><font size=2 face="sans-serif"> Thomas</font>
<br>
<br>
<br><font size=1 face="Arial">Mit freundlichen Grüßen / Kind regards</font>
<br>
<br><font size=1 face="Arial"><b>Thomas Lentz</b></font>
<br>
<br><font size=1 color=#0060a0 face="Arial">Senior IT Architect</font>
<br><font size=1 color=#0060a0 face="Arial">Global Business Services</font>
<br><font size=1 color=#0060a0 face="Arial">NGN Competence Center (</font><a href="www.ngn-factory.com"><font size=1 color=#0060a0 face="Arial">www.ngn-factory.com</font></a><font size=1 color=#0060a0 face="Arial">)</font>
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<td width=599 colspan=4 style="border-style:solid;border-color:#000000;border-width:0px 0px 0px 0px;padding:0px 0px;"><font size=1 color=#a2a2a2 face="Arial">IBM
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<br>
<br>
<br>
<br>
<br><font size=1 color=#5f5f5f face="sans-serif">From:
</font><font size=1 face="sans-serif">Gnana Guru Natarajan
<gnanaguru3012@gmail.com></font>
<br><font size=1 color=#5f5f5f face="sans-serif">To:
</font><font size=1 face="sans-serif">discussion@sipforum.org</font>
<br><font size=1 color=#5f5f5f face="sans-serif">Date:
</font><font size=1 face="sans-serif">27.09.2017 18:41</font>
<br><font size=1 color=#5f5f5f face="sans-serif">Subject:
</font><font size=1 face="sans-serif">[SIPForum-discussion]
rport and received parameter in Via header</font>
<br><font size=1 color=#5f5f5f face="sans-serif">Sent by:
</font><font size=1 face="sans-serif">discussion-bounces@sipforum.org</font>
<br>
<hr noshade>
<br>
<br>
<br><font size=3>Hi,</font>
<br>
<br><font size=3> What is the purpose of rport
and received parameter in sip via header? Will it be needed if sip client
is behind NAT router? If so, how router can process this sip header as
router only handle the IP header but cannot application layer header?</font>
<br>
<br><font size=3>Thanks,</font>
<br><font size=3>Gnana Guru N.</font><tt><font size=2>_______________________________________________<br>
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