<html xmlns:v="urn:schemas-microsoft-com:vml" xmlns:o="urn:schemas-microsoft-com:office:office" xmlns:w="urn:schemas-microsoft-com:office:word" xmlns:m="http://schemas.microsoft.com/office/2004/12/omml" xmlns="http://www.w3.org/TR/REC-html40"><head><meta http-equiv=Content-Type content="text/html; charset=us-ascii"><meta name=Generator content="Microsoft Word 14 (filtered medium)"><style><!--
/* Font Definitions */
@font-face
{font-family:Calibri;
panose-1:2 15 5 2 2 2 4 3 2 4;}
/* Style Definitions */
p.MsoNormal, li.MsoNormal, div.MsoNormal
{margin:0cm;
margin-bottom:.0001pt;
font-size:11.0pt;
font-family:"Calibri","sans-serif";
mso-fareast-language:EN-US;}
a:link, span.MsoHyperlink
{mso-style-priority:99;
color:blue;
text-decoration:underline;}
a:visited, span.MsoHyperlinkFollowed
{mso-style-priority:99;
color:purple;
text-decoration:underline;}
span.EmailStyle17
{mso-style-type:personal-compose;
font-family:"Calibri","sans-serif";
color:windowtext;}
.MsoChpDefault
{mso-style-type:export-only;
font-family:"Calibri","sans-serif";
mso-fareast-language:EN-US;}
@page WordSection1
{size:612.0pt 792.0pt;
margin:72.0pt 72.0pt 72.0pt 72.0pt;}
div.WordSection1
{page:WordSection1;}
--></style><!--[if gte mso 9]><xml>
<o:shapedefaults v:ext="edit" spidmax="1026" />
</xml><![endif]--><!--[if gte mso 9]><xml>
<o:shapelayout v:ext="edit">
<o:idmap v:ext="edit" data="1" />
</o:shapelayout></xml><![endif]--></head><body lang=EN-CA link=blue vlink=purple><div class=WordSection1><p class=MsoNormal>Folks;<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>I am attempting to deploy T.38 Fax (ZRTP Secure) with FreeSwitch / FusionPBX and am seeking system architectural advice regarding how to approach this.<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal><span style='color:red'>Question #1:</span> Recommended T.38 capable ATA (and settings) for reliable FAX.<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal><span style='font-size:14.0pt'>Approach #1 ZRTP mitm with T.38 SIP Extension (either T.38 capable ATA or soft endpoint) – preferred approach<o:p></o:p></span></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>T.38 SIP endpoint <-> FS#1 / mitm <-> cloud <-> FS#2 mitm <-> T.38 SIP endpoint<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>I am using a soft T.38 SIP endpoint, plugin for Windows Fax and Scan from faxback, available here:<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal><a href="http://www.faxback.com/Products/Trialware.aspx?NET_SAT_EDITION=Small%20Business">http://www.faxback.com/Products/Trialware.aspx?NET_SAT_EDITION=Small%20Business</a><o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>SIP Gateway, just prior to bridge:<o:p></o:p></p><p class=MsoNormal style='margin-left:36.0pt'><strong><span style='font-family:"Calibri","sans-serif"'><action application="export" data="fax_enable_t38_request=true"/></span></strong><br><strong><span style='font-family:"Calibri","sans-serif"'><action application="set" data="execute_on_answer=t38_gateway peer"/><o:p></o:p></span></strong></p><p class=MsoNormal><strong><span style='font-family:"Calibri","sans-serif"'><o:p> </o:p></span></strong></p><p class=MsoNormal><strong><span style='font-family:"Calibri","sans-serif"'>Extension, just prior to bridge:<o:p></o:p></span></strong></p><p class=MsoNormal><strong><span style='font-family:"Calibri","sans-serif"'><o:p> </o:p></span></strong></p><p class=MsoNormal style='margin-left:36.0pt'><strong><span style='font-family:"Calibri","sans-serif"'><action application="set" data="fax_enable_t38_request=true"/></span></strong><br><strong><span style='font-family:"Calibri","sans-serif"'><action application="set" data="execute_on_answer=t38_gateway self"/><o:p></o:p></span></strong></p><p class=MsoNormal><strong><span style='font-family:"Calibri","sans-serif"'><o:p> </o:p></span></strong></p><p class=MsoNormal><strong><span style='font-family:"Calibri","sans-serif"'>What I am seeing (two FS systems), each with T.38 soft extensions, attempting to fax each other.<o:p></o:p></span></strong></p><p class=MsoNormal><strong><span style='font-family:"Calibri","sans-serif"'><o:p> </o:p></span></strong></p><p class=MsoNormal><strong><span style='font-family:"Calibri","sans-serif"'> ZRTP negotiation fails (Max retransmissions fail) -> NOZRTP<o:p></o:p></span></strong></p><p class=MsoNormal><strong><span style='font-family:"Calibri","sans-serif"'> ONE SDP is T38Fax (extension or gateway), Other is PCMU/8000<o:p></o:p></span></strong></p><p class=MsoNormal><strong><span style='font-family:"Calibri","sans-serif"'> The extension of T.38 enters state [ready] and immediately hangs up, I assume from SDP mismatch<o:p></o:p></span></strong></p><p class=MsoNormal><strong><span style='font-family:"Calibri","sans-serif"'><o:p> </o:p></span></strong></p><p class=MsoNormal><span style='color:red'>Question #2:</span> Anyone successfully done this, if so, how?<span style='color:red'><o:p></o:p></span></p><p class=MsoNormal><span style='color:red'>Question #3:</span> Is what I am attempting architecturally possible? Can T.38 be mitm’d?<o:p></o:p></p><p class=MsoNormal><span style='color:red'>Question #4:</span> If so, advice regarding how to debug the ZRTP negotiation failure and SDP negotiation failure.<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal><span style='font-size:14.0pt'>Approach #2: FS terminates incoming T.38 fax, stores and forwards to fax extension, FS terminates outgoing T.38 fax, stores and forwards to SIP gateway to final destination.<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:14.0pt'><o:p> </o:p></span></p><p class=MsoNormal>T.38 SIP endpoint <-> FS#1 / terminate fax <-> FS#1 forward fax <-> cloud <-> FS#2 / terminate fax <-> FS#2 forward fax <-> T.38 SIP endpoint<o:p></o:p></p><p class=MsoNormal><span style='font-size:14.0pt'><o:p> </o:p></span></p><p class=MsoNormal><span style='color:red'>Question #5: </span><span style='color:black'>Will this work? Anyone done it, how? ZRTP gotcha’s?</span><strong><span style='font-family:"Calibri","sans-serif"'><o:p></o:p></span></strong></p><p class=MsoNormal><strong><span style='font-family:"Calibri","sans-serif"'><o:p> </o:p></span></strong></p><p class=MsoNormal>Thanks;<o:p></o:p></p><p class=MsoNormal>Bill<o:p></o:p></p></div></body></html>