[cisco-voip] Fwd: Cisco ATA Fax Confusion

[Rhodium]

It is an excellent resource but doesn't go into fax passthrough to the level of my question as my concern was regarding the interoperability between the two different pass through protocols and not fax relay.

So ATAs support modem passthrough and the difference between that and fax passthrough is that modem passthrough looks for phase reversals, but it falls back to fax passthrough if there are none. Am I correct in the fall back assumption?

Also, trying to work out how a Cisco VG224 configured for pass-through (protocols based) can receive faxes from ATAs supporting passthrough. Was wondering if there is some kind of interoperability going on here a new feature I wasn't aware of.

Guess, debugs will show that...

Jason

--- On Fri, 1/22/10, Ryan Ratliff <rratliff at cisco.com> wrote:

> From: Ryan Ratliff <rratliff at cisco.com>
> Subject: Re: [cisco-voip] Fwd:  Cisco ATA Fax Confusion
> To: "Rhodium" <rhodium_uk at yahoo.co.uk>
> Cc: cisco-voip at puck.nether.net, "Nick" <csvoip at googlemail.com>
> Date: Friday, January 22, 2010, 3:43 PM
> The fax section of the CUCM SRND is a
> very good resource for this.
> 
> The ATAs appear to support modem passthrough for fax only.
> 
> "T.38 fax relay is supported on most of the current Cisco
> voice gateways, especially those running Cisco IOS. Notable
> exceptions are the Cisco Analog Telephone Adaptors (ATAs)
> and legacy products such as the Cisco 6608, 6624, and
> DT-24/DE-30+.
> 
> Most Cisco voice gateways support Cisco fax relay, and it
> is the default fax transport method. Notable exceptions with
> regard to the support of Cisco fax relay are the Cisco
> AS5350 and AS5400 with Nextport DSP cards, the Cisco ATA,
> and the Cisco DT-24/DE-30+. Another exception is that the
> Cisco 2900 and 3900 Series gateways with the PVDM3 DSPs do
> not support Cisco fax relay.
> 
> Unlike T.38 fax relay, which uses an Unnumbered Datagram
> Protocol Transport Layer (UDPTL) header, Cisco fax relay
> utilizes the standard RTP header, which makes Cisco fax
> relay capable of secure fax transactions using Secure
> Real-Time Transport Protocol (SRTP).
> 
> Modem passthrough is supported by all current Cisco voice
> gateways, including the Cisco ATA as well as most legacy
> voice gateways."
> 
> http://www.cisco.com/en/US/docs/voice_ip_comm/cucm/srnd/7x/gateways.html#wp1046809
> 
> -Ryan
> 
> On Jan 22, 2010, at 10:08 AM, Rhodium wrote:
> 
> Hi All, Nick and Venkata,
> 
> Thanks for the feedback but do you have the issue of not
> being able train the faxes or missed pages?
> 
> I am still after an answer to my question about what fax
> protocol is actually supported on the ATAs and on the VG in
> SCCP mode as my theory does not relate to real life?
> 
> Regards,
> 
> Jason
> 
> 
> 
> 
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