[cisco-voip] Fwd: Cisco ATA Fax Confusion

[Ryan Ratliff]

The lack of hyphenation is because fax pass-through is modem passthrough, which is NSE based.   This call is working because the ATA passes  the fax tones on to the VG224 as NSEs and it recognizes them.

If we look at your config:
fax protocol t38 nse ls-redundancy 0 hs-redundancy 0 fallback pass-through g711ulaw

This means upon detection of the fax-tones (call outbound from VG224 to ATA) the VG will attempt to switch to T38.   The fallback pass-through means that if T38 fails it will send NSEs as well.  This is the part that is compatible with the ATA.

-Ryan

On Jan 22, 2010, at 1:42 PM, Rhodium wrote:

Hi Ryan,

I am using the terms as per the Cisco Press book "Fax, Modem, and Text for IP Telephony" by David Hanes and Gonzalo Salgueiro. Excellent reference!

I guess what is throwing me off is your lack of hyphenations in the terms pass-through and passthrough in your replies. I understand the following:

fax pass-through - Protocol based fax transmission
fax passthrough - NSE based fax transmission

As regards what I am seeing, yeah but the configuration doesn't imply that as one is setup for T.38 relay with pass-through fall back and the ATA is obviously only passthrough so I guess only a debug will answer that question as I was wondering whether the VG was falling back to NSE based passthrough for some reason.

To be honest, I wouldn't expect it to work at all so why I am asking this knowledgeable forum about it incase I missed something in the documentation.


Thank you for your reply as well as to all the other contributors.

Regards,

Jason