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<p class="MsoNormal"><span lang="EN-GB">Hello<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB">I am running a setup where calls from the outside are not encrypted with SRTP (from our SIP trunk), and locally (between phone & FS) they are.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB">I put in the vars.xml:<o:p></o:p></span></p>
<p class="MsoNormal" style="background:white"><span lang="EN-GB" style="font-size:10.0pt;font-family:"Courier New";color:black;background:#EFEFEF;mso-fareast-language:NL-BE"><</span><b><span lang="EN-GB" style="font-size:10.0pt;font-family:"Courier New";color:navy;background:#EFEFEF;mso-fareast-language:NL-BE">X-PRE-PROCESS
</span></b><b><span lang="EN-GB" style="font-size:10.0pt;font-family:"Courier New";color:blue;background:#EFEFEF;mso-fareast-language:NL-BE">cmd</span></b><b><span lang="EN-GB" style="font-size:10.0pt;font-family:"Courier New";color:green;background:#EFEFEF;mso-fareast-language:NL-BE">="set"
</span></b><b><span lang="EN-GB" style="font-size:10.0pt;font-family:"Courier New";color:blue;background:#EFEFEF;mso-fareast-language:NL-BE">data</span></b><b><span lang="EN-GB" style="font-size:10.0pt;font-family:"Courier New";color:green;background:#EFEFEF;mso-fareast-language:NL-BE">="rtp_secure_media=optional:AES_CM_128_HMAC_SHA1_80"</span></b><span lang="EN-GB" style="font-size:10.0pt;font-family:"Courier New";color:black;background:#EFEFEF;mso-fareast-language:NL-BE">/></span><span lang="EN-GB" style="font-size:10.0pt;font-family:"Courier New";color:black;mso-fareast-language:NL-BE"><o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB">This all works fine, however with one disturbing fact; when you pick up the call you hear a loud “static” noise. I think this is the phase where the suite is negotiated, because it’s the same as when we force SRTP on
FreeSWITCH and disable it in the phone (but then the call fails afterwards of course).<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB">So what I would need to accomplish:<o:p></o:p></span></p>
<ul style="margin-top:0cm" type="disc">
<li class="MsoListParagraph" style="margin-left:0cm;mso-list:l1 level1 lfo3"><span lang="EN-GB">Either the phone needs to negotiate the SRTP before it’s answered (is that even possible?), e.g. during ring<o:p></o:p></span></li><li class="MsoListParagraph" style="margin-left:0cm;mso-list:l1 level1 lfo3"><span lang="EN-GB">If the negotiation has to take place after answering, that it doesn’t generate this loud noise in the meantime.<o:p></o:p></span></li></ul>
<p class="MsoNormal"><span lang="EN-GB"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB">It could also be due to the used phone (Yealink, T42G and T46G). With RTX phones we didn’t have this issue yet but I only tested it with one device. But if someone has some pointers on what causes this…<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB">Thanks for your input!<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB">Regards<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB">Maarten<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB"><o:p> </o:p></span></p>
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