<p class="MsoPlainText">"A year ago", "September", "November"...
looks like there is no solid time domain event correlation to be had.</p>
<p class="MsoPlainText"> What would Chuck Norris do?<span style=""> </span>Bash in everyone's head at the same time,
knowing that one of them must be the bad guy.</p>
<br>-B<br><br><br><br><br><br><div class="gmail_quote">On Mon, Jan 24, 2011 at 10:24 AM, Mark Kent <span dir="ltr"><<a href="mailto:mark@noc.mainstreet.net">mark@noc.mainstreet.net</a>></span> wrote:<br><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">
I stumbled across a situation where a fax-to-email service gets<br>
inbound calls, from Carrier X, over a PRI into a cisco 5350 which then<br>
relays the calls, via an x-conn PRI, to a directly-attached linux box.<br>
This has worked for years.<br>
<br>
About a year ago, it was revealed that the above-mentioned PRI<br>
connects to the edge of Carrier X's SIP infrastructure. That is,<br>
calls start from some PSTN-connected fax machine, somewhere in the<br>
USA, go through a PSTN-to-SIP gateway, travel as SIP to the building<br>
where this cisco 5350 is, and then go through Carrier X's SIP-to-TDM<br>
equipment for delivery over the PRI to the cisco 5350.<br>
<br>
This led to some concern, since we all know that fax over SIP can be<br>
problematic. But everything was working, hundreds of faxes a day<br>
were pulsing through the system.<br>
<br>
Up until September the cisco 5350 was in the same building as Carrier<br>
X's TDM equipment. In late September, a point-to-point, B8ZS/ESF T1<br>
was used to extend the in-building cross-connect between Carrier X<br>
and the cisco 5350. The cisco 5350, and related servers, are now<br>
eight miles away (both endpoints in Manhattan, using VerizonBusiness<br>
for the T1, both endpoints "on-net", no ILEC involved).<br>
<br>
Since November, maybe half a percent of the faxes fail to work.<br>
They get a communication error at the start, at the modem negotiation.<br>
The T1 circuit is clean.<br>
<br>
Some people think that failures may not have been reported/noticed in<br>
October, but they occured nevertheless. This would suggest that the<br>
previous set-up was a very delicately balanced system and the moving<br>
of the cisco5350 eight miles away, necessitating the use of a T1 to<br>
carry the PRI to the new location, may be the root cause of the<br>
failures. Occam's razor reasoning supports this.<br>
<br>
The grassy knoll people believe that, in November, Carrier X started<br>
an effort to wring more out of their SIP network. Perhaps they started<br>
using different peers in various parts of the country. Maybe their<br>
PSTN-to-SIP gateways were tuned to use less bandwidth. When asked,<br>
Carrier X answered a different question, in a fashion similar to a<br>
politician.<br>
<br>
I'm wondering whether any experts here have an opinion to offer?<br>
<br>
Thanks,<br>
-mark<br>
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</blockquote></div><br>