Re: Fax Issues Site Wide : Request Assistance

What is interesting about faxing is actually very little, but here are
some things that may help you troubleshoot:

-A lot of faxes will work over straight G.711. The difference between
G.711 and 'passthrough' are DTMF is disabled, larger jitter buffer,
and no echo cancellation.
-Switching from G.711/G.729 to fax passthrough or relay is the
responsibility of the called TDM endpoint. For inbound faxes this
would be your VG224. As well, any other terminating TDM point in the
provider network.
-Cisco fax relay is the default faxing protocol on routers. It has
been discontinued in the latest hardware versions (PVDM3).

Things that could explain your odd outage:
-A piece of provider gear was replaced that no longer correctly
signals to the originating side that a fax is going on.
-The provider network has changed ever so slightly where normal G.711
isn't good enough any longer, but you only had faxing configured one
way.
-Someone changed a config somewhere so that your fax negotiation is
now asymmetric and no longer works both ways. This could be a DSP
upgrade, gateway configuration change, gateway version change, etc.

-nick

On Mon, Aug 8, 2011 at 11:30 AM, Radioactive Frog <pbhatkoti_at_gmail.com> wrote:
> I see this issue every now and then. I can guarantee this was caused by
> asymmetric routing or routing issue.
> latest I saw this was a week ago! so far this year I have seen this about 5
> times. All of them being routing issue - l2/l3 changes.
>
> On Tue, Aug 9, 2011 at 12:42 AM, Roden, Miles <mroden_at_oceaneering.com>wrote:
>
>> We have begun experiencing an issue that is affecting our entire campus in
>> Houston, TX. Through some of our in house techs, I was advised to send an
>> email to you guys to see if anyone can shed some light on our situation.
>> Appreciate any assistance or insight.
>>
>> Issue Summary :
>> We have a 3 Server cluster of CM7, with multiple VG devices registered as
>> H323 gateways. We use the VG's strictly for fax interfaces. A week ago we
>> lost all inbound faxing capabilities with no changes on our side. We have
>> an
>> active ticket with Cisco but they have yet to come up with a conclusion.
>> PRI
>> Provider ATT is supposedly checking their side as well. Have done packet
>> traces, RTMT, you name it. Outbound appears intact as well as internal fax
>> to fax. To take the CM out of the loop, I set up a dial-peer from PRI-GW
>> direct to VG224 and still retained same issues.
>>
>> I can supply any info, traces, logs you need.
>>
>> Miles Roden
>> Communications Project Manager
>> Oceaneering International
>> o: 713-329-4318
>>
>>
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Received on Mon Aug 08 2011 - 21:46:13 ART