[asterisk-users] FFA SendFax rejects T.38 reINVITE (488 Not acceptable here)

[Kevin P. Fleming]

On 10/19/2010 02:17 PM, VoIP Question wrote:
> Fair enough Kevin :-) It's just that your documentation for this product
> is so limited that without extensive search online and the assistance of
> others, it would have been impossible for us to make any progress and we
> haven't reached the ReceiveFax part yet ;)

The issue you are having is not related to Fax For Asterisk; it's a T.38
negotiation problem, that would occur with app_fax as well. Did you try
using app_fax (including with Asterisk 1.6.2.x) to try to narrow down
whether the problem was in Asterisk or in Fax For Asterisk?

> 
> Anyway, specifically, we installed Asterisk 1.6.2.11. As far as we
> know/understand, the SendFax application is running.
> 
> This is the full log of the call, until it's rejected for the first
> time. The remote switch resends the INVITEs a few more times, but it's
> all the same, so I didn't include it:
> 
> sip*CLI>     -- Attempting call on Local/12345678 at outgoing for
> s at outboundfax:1 (Retry 1)
> sip*CLI>     -- Executing [12345678 at outgoing:1]
> Dial("Local/12345678 at outgoing-2c36;2", "SIP/12345678 at main,50,tTr") in
> new stack

You have a 'Local' channel in between SendFAX and the SIP channel to
your other endpoint. In Asterisk 1.6.2.11, chan_local was not properly
aware of T.38 negotiation, so it ends up acting as a sort of 'firewall'
between the endpoints.

This was fixed in Asterisk 1.6.2.12 and later releases, so if you were
running the current version, you wouldn't have experienced this specific
problem. This was listed in the ChangeLog for 1.6.2.12, but
unfortunately the commit message the developer wrote did not explain why
the change was made or what problem it was addressing, so you wouldn't
have noticed it.

In any case, upgrading to 1.6.2.12 or later will cure this problem.

-- 
Kevin P. Fleming
Digium, Inc. | Director of Software Technologies
445 Jan Davis Drive NW - Huntsville, AL 35806 - USA
skype: kpfleming | jabber: kfleming at digium.com
Check us out at www.digium.com & www.asterisk.org