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<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>All your questions are around layer1, a show controller or show
service-module would indicate if clocking or timing or other layer1 issues. You
have to look at both sides. Your side may be clean but the other side dirty.<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>Usually a TTC T-Berd with Y-Cable in the middle would help with
analysis. You can even listen in to troubleshoot. You can rent T-Berd for
a month for less than $250 from Renfro Test Equipment (Google).<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>Other answers inline<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<div style='border:none;border-top:solid #B5C4DF 1.0pt;padding:3.0pt 0in 0in 0in'>
<p class=MsoNormal><b><span style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'>From:</span></b><span
style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'>
cisco-voip-bounces@puck.nether.net [mailto:cisco-voip-bounces@puck.nether.net] <b>On
Behalf Of </b>Jeff Anderson<br>
<b>Sent:</b> Wednesday, May 06, 2009 5:00 PM<br>
<b>To:</b> cisco-voip@puck.nether.net<br>
<b>Subject:</b> [cisco-voip] Special considerations for IAD or
PRInetwork-emulation on Cisco hardware...<o:p></o:p></span></p>
</div>
<p class=MsoNormal><o:p> </o:p></p>
<div>
<p class=MsoNormal>I have a couple of customers who are experiencing poor audio
using an IAD to connect their PBX to our h.323 PSTN GW.<o:p></o:p></p>
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<div>
<p class=MsoNormal> <o:p></o:p></p>
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<p class=MsoNormal>Basic Layout.<o:p></o:p></p>
</div>
<div>
<p class=MsoNormal> <o:p></o:p></p>
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<div>
<p class=MsoNormal>Customer PBX PRI > IAD PRI (Network-emulate) converted to
VoIP > MPLS enabled T1 > Core > AS5850 (VoIP converted to
TDM) > PSTN.<o:p></o:p></p>
</div>
<div>
<p class=MsoNormal> <o:p></o:p></p>
</div>
<div>
<p class=MsoNormal>The customer reports that poor audio is experienced inbound
into their PBX. They say their outbound audio is okay. This doesnt happen on
every call but we do have more than one customer reporting the issue.<o:p></o:p></p>
</div>
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<p class=MsoNormal> <o:p></o:p></p>
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<p class=MsoNormal>The audio can be described anywhere from echo, cutting out
or distorted audio. The problem has also been reported by users who have 38xx
series gateways so i dont think the problem is IAD specific. The AS5850 is a
shared device used by many different customers, the majority of which connect
using Cisco IP phones and this demographic of customers are not reporting
the problem.<o:p></o:p></p>
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<p class=MsoNormal> <o:p></o:p></p>
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<div>
<p class=MsoNormal>I have done packet captures on the AS5850 and there is no
packet loss reported, the packets arrive in sequence and the jitter is very
low.<o:p></o:p></p>
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<div>
<p class=MsoNormal> <o:p></o:p></p>
</div>
<div>
<p class=MsoNormal>In my testing, I have found double-talk to cause the far end
audio (AS5850) to cut-out. All the packets arrive but they contain a payload
value of 7F. Some improvement can be made to this condition by disabling
non-linear progression. <o:p></o:p></p>
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<p class=MsoNormal> <o:p></o:p></p>
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<div>
<p class=MsoNormal> <o:p></o:p></p>
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<p class=MsoNormal> <o:p></o:p></p>
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<div>
<p class=MsoNormal>My questions for the community are related to experiences or
lessons learned from using PRI network emulate.<o:p></o:p></p>
</div>
<div>
<p class=MsoNormal> <o:p></o:p></p>
</div>
<div>
<p class=MsoNormal>Can there be too many echo cancellers in the call flow?
(i.e. Customer PBX UC500 with Cisco PRI, IAD PRI, AS5850 PRI all with echo
cancellers)<o:p></o:p></p>
</div>
<div>
<p class=MsoNormal> <span style='color:#1F497D'>They are usually local
link significant. Bad DSP micro code can cause the issues you are reporting. I’ve
done PCM captures that were good yet the DSP turned out to be bad.</span><o:p></o:p></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
</div>
<div>
<p class=MsoNormal>Does the cable length command have any bearing on voice
quality?<o:p></o:p></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>I haven’t seen the cable length command fix quality issues<o:p></o:p></span></p>
</div>
<div>
<p class=MsoNormal> <o:p></o:p></p>
</div>
<div>
<p class=MsoNormal>Are there any special commands i should enter when
connecting back to back wth a T1 cable (echo-cancel coverage, nlp, etc)?<o:p></o:p></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>Who is clocking? Network vs user side? Clock slips, line code violations,
etc would create the problems you describe<o:p></o:p></span></p>
</div>
<div>
<p class=MsoNormal> <o:p></o:p></p>
</div>
<div>
<p class=MsoNormal>Is a 2 pair sheilded T1 cable necessary for the PRI back to
back connection of less than 20 ft?<o:p></o:p></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>I always use shielded T1, who knows when EMF will be present? A
1 ft cable wrapped around a ballast would be bad..<o:p></o:p></span></p>
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<p class=MsoNormal> <o:p></o:p></p>
</div>
<div>
<p class=MsoNormal> <o:p></o:p></p>
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<div>
<p class=MsoNormal>Any insight or suggestions would be greatly appreciated. <o:p></o:p></p>
</div>
<div>
<p class=MsoNormal> <o:p></o:p></p>
</div>
<div>
<p class=MsoNormal>Thanks,<o:p></o:p></p>
</div>
<div>
<p class=MsoNormal> <o:p></o:p></p>
</div>
<div>
<p class=MsoNormal>Jeff <o:p></o:p></p>
</div>
<div>
<p class=MsoNormal> <o:p></o:p></p>
</div>
<div>
<p class=MsoNormal> <o:p></o:p></p>
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