[asterisk-users] T.38 gateway ATA

[Bryant Zimmerman]

----------------------------------------
 From: "Jeff LaCoursiere" <jeff at sunfone.com>
Sent: Tuesday, September 25, 2012 11:05 AM
To: asterisk-users at lists.digium.com
Subject: Re: [asterisk-users] T.38 gateway ATA

On 09/25/2012 09:26 AM, Bryant Zimmerman wrote:
 Jeff

Can you please clarify your layout? If you have an asterisk 1.8 (I would 
use 10 for this if possible) server why can't you just take the gateway 
call on that via a sip trunk. If you are coming in from and land line and 
want to do t.38 to the asterisk 1.8 server you would need a FXO t.38 
gateway. Based on your description I am not sure what your sources are and 
what your final desired destination is. Please be specific with your 
response.  We do t.38 all the time and have great success with it but the 
success is in the setup and control of the endpoints (gateways and ATAs)

Thanks

Bryant Zimmerman (ZK Tech Inc.)
616-855-1030 Ext. 2003 

----------------------------------------
 From: "Jeff LaCoursiere" <jeff at sunfone.com>
Sent: Monday, September 24, 2012 9:20 PM
To: "Asterisk Users Mailing List - Non-Commercial Discussion" 
<asterisk-users at lists.digium.com>
Subject: [asterisk-users] T.38 gateway ATA

Hoping for some clarification. I would like to setup a NORMAL (not 
T.38) fax machine on an ATA, and have the ATA be a T.38 gateway to a 
remote asterisk (1.8) server, which is doing T.38 relay (passthru) to a 
provider.

Some amount of googling today seems to imply that most ATAs are just 
T.38 passthru devices, and expect a T.38 capable fax machine, otherwise 
just fallback to ulaw (and mostly fail, in my experience so far).

So does anyone use an ATA that actually does the gateway transcoding to 
a normal fax machine? Or am I barking up the wrong tree?

Thanks!

j

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Hi Bryan,

To follow an inbound fax call, our intended setup would be:

Our upstream sends a T.38 call to our border asterisk (1.8) server, which 
creates another T.38 call to the customer's hosted asterisk (1.8) instance, 
which creates another T.38 call to the ATA, which is over the Internet to 
their location.  The ATA would do the transcoding (is that even the 
appropriate term in this case?) to T.30, to the FXS connected normal fax 
machine.

Its that last bit that I am having trouble confirming is a feature of any 
mainstream ATA.  When I dug into it yesterday it seems that the mainstream 
ATAs will passthru T.38, expecting the connected fax machine to work with 
T.38 natively.  I can't depend on that.  The asterisk servers are all 
remote, and though I could presumably do the gateway on the asterisk server 
I would then have a ulaw fax call over the internet to the ATA, which in my 
experience has not been very reliable.

Of course I will need outbound faxing to follow the reverse path, letting 
the ATA turn the T.30 outbound fax call into T.38, which travels through 
our various asterisk servers to the upstream provider...

So in a nutshell, is there anyone using an ATA as the *gateway* rather than 
passthru?  I feel I am still not being clear... does that help?

Thanks,

j

Jeff

In your call stream you must make sure that all asterisk systems have the 
proper configurations for T.38 and that spandsp is loaded on the systems. 
Each peer entry must have the correct setup and the correct rtp port ranges 
must be set on all asterisk servers. Each server must have the correct 
configurations for their firewalls as well. I would flatten this to start. 
If possible connect the ATA's directly as a registration to your proxy. You 
will likely have better results. We have had the best luck with ATA's from 
audio codes and grandstream currently the HT-701, 702 have been working 
well. You must get the mix right and them keep it flat. Every time you 
allow user to drop an asterisk box between you and the ata you will give 
yourself a greater issues as they must become an asterisk t.38 expert to 
get the deployment to work or you must take it on. Hope this helps.  T.38 
works well when you get the right mix and control it. 

Bryant
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