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<div>Have you tried the opposite, disable T.38 and use G711a/u for the payload. </div>
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<div>We have had far greater success with the G711a/u RTP. T.38 still seems to be very hit and miss cross devices be it ATA or even a real fax machine. </div>
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<div>Cheers</div>
<div>Greg</div>
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<div id="x_divRplyFwdMsg" dir="ltr"><font face="Calibri, sans-serif" color="#000000" style="font-size:11pt"><b>From:</b> VoiceOps <voiceops-bounces@voiceops.org> on behalf of Nelson Hicks <nelsonh@socket.net><br>
<b>Sent:</b> Saturday, October 1, 2016 4:47:30 AM<br>
<b>To:</b> voiceops@voiceops.org<br>
<b>Subject:</b> [VoiceOps] Problems with T.38 fax with Grandstream GXW-4248</font>
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<div class="PlainText">We have a customer with multiple Grandstream GXW-4248 voice gateways
<br>
that wants to use T.38 for sending and receiving faxes. They are running <br>
the most recent release (1.0.5.16). We have tested this successfully <br>
with other devices, including a Grandstream HT-702 and a Grandstream <br>
GXW-4004, but when configuring the Grandstream GXW-4248 the same way, <br>
the audio from the Grandstream to the fax machine cuts out at the <br>
renegotiation to T.38 and does not resume. When looking at a packet <br>
capture of the fax call, the Re-INVITE appears successful, but the first <br>
and only UDPTL packet sent by the Grandstream is reported as malformed <br>
by Wireshark:<br>
<br>
ITU-T Recommendation T.38<br>
[Stream setup by SDP (frame 510)]<br>
[Stream frame: 510]<br>
[Stream Method: SDP]<br>
UDPTLPacket<br>
seq-number: 32768<br>
primary-ifp-packet<br>
type-of-msg: t30-indicator (0)<br>
something unknown here [too long <br>
integer(per_normally_small_nonnegative_whole_number)]<br>
[Expert Info (Warn/Undecoded): something unknown <br>
here [too long integer(per_normally_small_nonnegative_whole_number)]]<br>
[something unknown here [too long <br>
integer(per_normally_small_nonnegative_whole_number)]]<br>
[Severity level: Warn]<br>
[Group: Undecoded]<br>
[Malformed Packet: T.38]<br>
[Expert Info (Error/Malformed): Malformed Packet (Exception occurred)]<br>
[Malformed Packet (Exception occurred)]<br>
[Severity level: Error]<br>
[Group: Malformed]<br>
<br>
Does anyone have any experience with trying to use T.38 with a <br>
Grandstream GXW-4248?<br>
<br>
Thanks,<br>
<br>
<br>
-- <br>
Nelson Hicks<br>
Network Operations<br>
SOCKET<br>
(573) 817-0000 ext. 210<br>
nelsonh@socket.net<br>
<br>
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