[cisco-voip] SG3 Faxing and IOS v15.1 (new thread)

[Carter, Bill]

Warning for the ISR G2 routers. I have a 2921 trying to do T.38 faxing
directly from FXS to PRI port using H.323. The ISR G2 routers do not
support Cisco Fax Relay. I had the standard T.38 configuration but Faxes
were failing. The Gateway was trying to use Cisco Fax Relay (IOS vs.
hardware/DSP support) but the gateway/DSPs aren't able to do it.  Fix is
"fax rate disable" on the dial-peers.

 

Bug ID CSCtc98074

 

I'm using 15.0(1)M1. A future release will prevent the Gateway from
attempting Cisco Fax Relay.

 

From: cisco-voip-bounces at puck.nether.net
[mailto:cisco-voip-bounces at puck.nether.net] On Behalf Of Nick Matthews
Sent: Friday, April 09, 2010 9:21 AM
To: Lelio Fulgenzi
Cc: cisco-voip voyp list
Subject: Re: [cisco-voip] SG3 Faxing and IOS v15.1 (new thread)

 

The feature is a DSP-software feature in 15.1(1)T.  This means it should
not be protocol dependent.  And though it is a DSP feature, it is still
not hardware dependent (per our last thread).

To my recollection, you should be able to use fax-passthrough with G711
with CUCM.  I seem to remember doing this many times, but the only
scenario I can't remember if it works correctly is G729->G711 switchover
with CUCM with passthrough.

The modem passthrough recommendation may be based in the pre-SG3 era,
and not be updated in the document.  The cisco.com fax documents aren't
particularly great sometimes.  I will be interested to see whether or
not the SG3 makes T38 more stable.  My thought it yes, and I would
personally start using T38 as my default rather than modem passthrough
with this new feature.

Modem passthrough pseudo-supported SG3 before.  Sometimes it would work,
sometimes not, because the DSPs were incapable of promising SG3 speeds.
That should also be changed now, as they support 56k speeds.

-nick




On Fri, Apr 9, 2010 at 9:54 AM, Lelio Fulgenzi <lelio at uoguelph.ca>
wrote:

I thought I'd start a new thread to help with future searches.

I took a closer look at that link I sent out earlier, the one that
pointed me to CUBE configuration, and it turns out there is a section in
there that talks about:

________________________________

SG3 Fax Support on Cisco TDM-IP Voice Gateways and Cisco UBE Platforms 

http://www.cisco.com/en/US/docs/ios/voice/cube/configuration/guide/vb-gw
-config.html#wp1423706

________________________________

 

While it goes in depth about relay, for fax pass-through, it simply
points to an old v12.4T document (link
<http://www.cisco.com/en/US/docs/ios/voice/fax/configuration/guide/vf_cf
g_fx_passthr_ps6441_TSD_Products_Configuration_Guide_Chapter.html> ).
The new one
<http://www.cisco.com/en/US/docs/ios/voice/fax/configuration/guide/vf_cf
g_fx_passthr_ps10592_TSD_Products_Configuration_Guide_Chapter.html>
(for v15.1) doesn't seem to go into any specific discussion about SG3
speeds, in fact, all it talks about is SG3 downgrading to G3.

In reading it more closely, it mentions only: MGCP, H323, and SIP. Is
SCCP out?

In reading it even more closely, it mentions that if you're using all
Cisco gateways, you should use modem passthrough.

 

Note Error! Filename not specified.Modem pass-through is preferred if
all of the involved gateways are Cisco IOS gateways.


And even more reading says if you're using CCM, you MUST use modem
passthrough.

Note Error! Filename not specified.If you need to configure fax
pass-through to work with Cisco CallManager (CCM), you must use the
modem passthrough nse command. The fax protocol pass-through command
does not work with CCM, which relies on NSE information. 


So what's the deal? 

*	Is SG3 supported on modem passthrough which I now must use? 
*	Does that mean I can stick with SCCP on my VG224, since SCCP
supports modem passthrough?









 


keywords: super G3 faxing fas passthrough fax pass-through confusing

---
Lelio Fulgenzi, B.A.
Senior Analyst (CCS) * University of Guelph * Guelph, Ontario N1G 2W1
(519) 824-4120 x56354 (519) 767-1060 FAX (JNHN)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Cooking with unix is easy. You just sed it and forget it. 
                              - LFJ (with apologies to Mr. Popeil)


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