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

[Lelio Fulgenzi]

Thanks for this Nick. Documentation errors cause a bit of an issue, since that's where the TAC looks for support entitlement. This occurs mainly in the non-U.S. based support centres where if it is not on the data sheet, they're not helping. I usually get things escalated back into the U.S. and the TAC engineers are more "investigative" and help figuring things out. 

I like the idea of SCCP since it simplifies configuration, procedures, etc. But if I need a separate stack of MGCP based VG224s for faxing, I can do that too. Not a big deal. Not sure how SRST would work in a case like that, guess I would need to create dial-peers for inbound and outbound calls. More reason for SCCP. 

I guess I can just try configuring things on my spare VG224 and router and see how things go. Call up the TAC if I have problems and see what they say. 

Thanks again, Lelio 



----- Original Message ----- 
From: "Nick Matthews" <matthnick at gmail.com> 
To: "Lelio Fulgenzi" <lelio at uoguelph.ca> 
Cc: "cisco-voip voyp list" <cisco-voip at puck.nether.net> 
Sent: Friday, April 9, 2010 10:20:48 AM GMT -05:00 US/Canada Eastern 
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 ). The new one (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 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 If you need to configure fax pass-through to work with Cisco CallManager (CCM), you must use the modem passthrough nse command. The f ax 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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