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<TITLE>Bypass media and NAT Traversal with Aastra</TITLE>
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<P DIR=LTR><SPAN LANG="en-us"><FONT FACE="Calibri">Hi,</FONT></SPAN><SPAN LANG="en-us"></SPAN></P>
<P DIR=LTR><SPAN LANG="en-us"><FONT FACE="Calibri">Is this a bug? (just kidding)</FONT></SPAN><SPAN LANG="en-us"></SPAN></P>
<P DIR=LTR><SPAN LANG="en-us"><FONT FACE="Calibri">As</FONT></SPAN><SPAN LANG="en-us"> <FONT FACE="Calibri">the number of extensions we serve increase</FONT></SPAN><SPAN LANG="en-us"><FONT FACE="Calibri">s</FONT></SPAN><SPAN LANG="en-us"><FONT FACE="Calibri">, w</FONT></SPAN><SPAN LANG="en-us"><FONT FACE="Calibri">e</FONT></SPAN><SPAN LANG="en-us"><FONT FACE="Calibri">’</FONT></SPAN><SPAN LANG="en-us"><FONT FACE="Calibri">re trying to avoid</FONT></SPAN><SPAN LANG="en-us"> <FONT FACE="Calibri">saturating our</FONT></SPAN><SPAN LANG="en-us"> <FONT FACE="Calibri">local</FONT></SPAN><SPAN LANG="en-us"> <FONT FACE="Calibri">bandwidth by</FONT></SPAN><SPAN LANG="en-us"> <FONT FACE="Calibri">proxying all of the media between endpoints</FONT></SPAN><SPAN LANG="en-us"><FONT FACE="Calibri">. This seems to work fine with the Link</FONT></SPAN><SPAN LANG="en-us"><FONT FACE="Calibri">s</FONT></SPAN><SPAN LANG="en-us"><FONT FACE="Calibri">ys devices but not with Aastra</FONT></SPAN><SPAN LANG="en-us"><FONT FACE="Calibri"> in all scenarios.</FONT></SPAN><SPAN LANG="en-us"><FONT FACE="Calibri"> The Aastras are configured with the NAT IP</FONT></SPAN><SPAN LANG="en-us"> <FONT FACE="Calibri">field populated</FONT></SPAN><SPAN LANG="en-us"><FONT FACE="Calibri"> appropriately</FONT></SPAN><SPAN LANG="en-us"><FONT FACE="Calibri"> and Rport (RFC 3581) enabled.</FONT></SPAN><SPAN LANG="en-us"></SPAN></P>
<P DIR=LTR><SPAN LANG="en-us"><FONT FACE="Calibri">The FS</FONT></SPAN><SPAN LANG="en-us"><FONT FACE="Calibri"> server is behind a NAT firewall with SIP and RTP port</FONT></SPAN><SPAN LANG="en-us"><FONT FACE="Calibri"> ranges</FONT></SPAN><SPAN LANG="en-us"><FONT FACE="Calibri"> forwarded to it. There are endpoints here</FONT></SPAN><SPAN LANG="en-us"> <FONT FACE="Calibri">on the same network as the switch, and there are remote endpoints behind their o</FONT></SPAN><SPAN LANG="en-us"><FONT FACE="Calibri">wn NAT firewalls. Everything works</FONT></SPAN><SPAN LANG="en-us"> <FONT FACE="Calibri">fine in Proxy Media mode</FONT></SPAN><SPAN LANG="en-us"><FONT FACE="Calibri"> but</FONT></SPAN><SPAN LANG="en-us"><FONT FACE="Calibri"></FONT></SPAN><SPAN LANG="en-us"> <FONT FACE="Calibri">i</FONT></SPAN><SPAN LANG="en-us"><FONT FACE="Calibri">n bypass mode</FONT></SPAN><SPAN LANG="en-us"><FONT FACE="Calibri"> we see the following behavior</FONT></SPAN><SPAN LANG="en-us"><FONT FACE="Calibri">:</FONT></SPAN></P>
<P DIR=LTR><SPAN LANG="en-us"></SPAN></P>
<P DIR=LTR><SPAN LANG="en-us"><FONT FACE="Calibri">Scenario 1</FONT></SPAN><SPAN LANG="en-us"><FONT FACE="Calibri">:</FONT></SPAN></P>
<P DIR=LTR><SPAN LANG="en-us"><FONT FACE="Calibri">Remote</FONT></SPAN><SPAN LANG="en-us"> <FONT FACE="Calibri">endpoint places a call to PSTN, FS negotiates bypass media between remote endpoint and</FONT></SPAN><SPAN LANG="en-us"> <FONT FACE="Calibri">PSTN gateway. Call</FONT></SPAN><SPAN LANG="en-us"> <FONT FACE="Calibri">succeeds</FONT></SPAN><SPAN LANG="en-us"><FONT FACE="Calibri">.</FONT></SPAN></P>
<P DIR=LTR><SPAN LANG="en-us"><FONT FACE="Calibri">Scenario 2:</FONT></SPAN></P>
<P DIR=LTR><SPAN LANG="en-us"><FONT FACE="Calibri">Remote endpoint places a call to another remote endpoint on same LAN</FONT></SPAN><SPAN LANG="en-us"><FONT FACE="Calibri">. Call succeeds.</FONT></SPAN></P>
<P DIR=LTR><SPAN LANG="en-us"><FONT FACE="Calibri">Scenario 3:</FONT></SPAN></P>
<P DIR=LTR><SPAN LANG="en-us"><FONT FACE="Calibri">Local endpoint places a call to PSTN gateway. Call succeeds.</FONT></SPAN></P>
<P DIR=LTR><SPAN LANG="en-us"><FONT FACE="Calibri">Scenario</FONT></SPAN><SPAN LANG="en-us"> <FONT FACE="Calibri">4</FONT></SPAN><SPAN LANG="en-us"><FONT FACE="Calibri">:</FONT></SPAN></P>
<P DIR=LTR><SPAN LANG="en-us"><FONT FACE="Calibri">Remote endpoint places a call to local endpoint</FONT></SPAN><SPAN LANG="en-us"><FONT FACE="Calibri"> (or vice versa)</FONT></SPAN><SPAN LANG="en-us"><FONT FACE="Calibri">. Call</FONT></SPAN><SPAN LANG="en-us"><FONT FACE="Calibri"> fails with no audio</FONT></SPAN><SPAN LANG="en-us"><FONT FACE="Calibri"> with Aastra devices</FONT></SPAN><SPAN LANG="en-us"><FONT FACE="Calibri"> on both ends</FONT></SPAN><SPAN LANG="en-us"><FONT FACE="Calibri">, but if one of the endpoints</FONT></SPAN><SPAN LANG="en-us"><FONT FACE="Calibri"></FONT></SPAN><SPAN LANG="en-us"> <FONT FACE="Calibri">is a LinkSys,</FONT></SPAN><SPAN LANG="en-us"> <FONT FACE="Calibri">the</FONT></SPAN><SPAN LANG="en-us"> <FONT FACE="Calibri">cal</FONT></SPAN><SPAN LANG="en-us"><FONT FACE="Calibri">l succeeds</FONT></SPAN><SPAN LANG="en-us"><FONT FACE="Calibri">.</FONT></SPAN></P>
<P DIR=LTR><SPAN LANG="en-us"><FONT FACE="Calibri">I realize that I should be able to solve this problem with a</FONT></SPAN><SPAN LANG="en-us"> <FONT FACE="Calibri">local</FONT></SPAN><SPAN LANG="en-us"> <FONT FACE="Calibri">SBC</FONT></SPAN><SPAN LANG="en-us"><FONT FACE="Calibri"> like OpenSIPS/RTPproxy</FONT></SPAN><SPAN LANG="en-us"><FONT FACE="Calibri">,</FONT></SPAN><SPAN LANG="en-us"><FONT FACE="Calibri"> but</FONT></SPAN><SPAN LANG="en-us"> <FONT FACE="Calibri">in the meantime I</FONT></SPAN><SPAN LANG="en-us"> <FONT FACE="Calibri">was hoping that</FONT></SPAN><SPAN LANG="en-us"> <FONT FACE="Calibri">there</FONT></SPAN><SPAN LANG="en-us"> <FONT FACE="Calibri">might be a setting that I was overlooking with the Aastra.</FONT></SPAN><SPAN LANG="en-us"><FONT FACE="Calibri"> When I look at the SIP traffic for the call, FS appears to be negotiating the addresses/ports properly so I</FONT></SPAN><SPAN LANG="en-us"><FONT FACE="Calibri"> suspect that this problem is related to</FONT></SPAN><SPAN LANG="en-us"> <FONT FACE="Calibri">Aastra</FONT></SPAN><SPAN LANG="en-us"><FONT FACE="Calibri">’</FONT></SPAN><SPAN LANG="en-us"><FONT FACE="Calibri">s inability to deal with</FONT></SPAN><SPAN LANG="en-us"> <FONT FACE="Calibri">symmetric NAT. The</FONT></SPAN><SPAN LANG="en-us"> <FONT FACE="Calibri">Linksys</FONT></SPAN><SPAN LANG="en-us"> <FONT FACE="Calibri">devices</FONT></SPAN><SPAN LANG="en-us"><FONT FACE="Calibri"> seem to</FONT></SPAN><SPAN LANG="en-us"> <FONT FACE="Calibri">be able to</FONT></SPAN><SPAN LANG="en-us"> <FONT FACE="Calibri">deal with it</FONT></SPAN><SPAN LANG="en-us"><FONT FACE="Calibri"> with FS</FONT></SPAN><SPAN LANG="en-us"><FONT FACE="Calibri">’</FONT></SPAN><SPAN LANG="en-us"><FONT FACE="Calibri"> help, presumably by doing some</FONT></SPAN><SPAN LANG="en-us"> <FONT FACE="Calibri">UDP</FONT></SPAN><SPAN LANG="en-us"> <FONT FACE="Calibri">hole-punching.</FONT></SPAN><SPAN LANG="en-us"></SPAN></P>
<P DIR=LTR><SPAN LANG="en-us"><I></I></SPAN><SPAN LANG="en-us"><I></I></SPAN><I><SPAN LANG="en-us"></SPAN></I><I><SPAN LANG="en-us"><FONT FACE="Times New Roman">Phil Quesinberry</FONT></SPAN></I><SPAN LANG="en-us"></SPAN><SPAN LANG="en-us"></SPAN><SPAN LANG="en-us"></SPAN></P>
<P DIR=LTR><SPAN LANG="en-us"><FONT SIZE=2 FACE="Arial">Q Systems Engineering, Inc.</FONT></SPAN></P>
<P DIR=LTR><SPAN LANG="en-us"><FONT SIZE=2 FACE="Arial">Electronic Controls and Embedded Systems Development</FONT></SPAN></P>
<P DIR=LTR><SPAN LANG="en-us"><FONT SIZE=2 FACE="Arial">(410) 969-8002</FONT></SPAN></P>
<P DIR=LTR><SPAN LANG="en-us"></SPAN><A HREF="http://www.qsystemsengineering.com"><SPAN LANG="en-us"></SPAN><SPAN LANG="en-us"><U></U></SPAN><U><SPAN LANG="en-us"></SPAN></U><U><SPAN LANG="en-us"><FONT COLOR="#0000FF" SIZE=2 FACE="Arial">http://www.qsystemsengineering.com</FONT></SPAN></U><SPAN LANG="en-us"></SPAN></A><SPAN LANG="en-us"></SPAN><SPAN LANG="en-us"></SPAN><SPAN LANG="en-us"></SPAN></P>
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