asterisk users - Dec 2009 - T38 Passthrough 1.6.1.12-rc1 Good Results

Hi All,

I've been knee deep in T38 faxing for a couple of weeks now, trying to
find a version of Asterisk that would pass through T38 with an
Audiocodes Mediant 1000 and MP203 ATA.  I had problems with 1.6.0.x
through 1.6.1.10.  Tested 6 different versions.  Either it just would
not work or fail back to G.711, or re-invite with wrong
T38FaxMaxDatagram sizes, faxes would work one-way and not the other,
and so on, issue after issue.

After trading some emails with the dev list, I learned a bit more
about what a good T38 negotiation should look like which helped out
quite a bit.  I started reading the changelog for the various versions
of 1.6.0.x and 1.6.1.x, focusing on chan_sip updates and fixes.  There
have been a lot of updates regarding T38, tweaks, patches, adding
functionality, and there was a total re-write of the stack as well.
All this within the past few months.

Just two days ago 1.6.1.12-rc1 was uploaded, changelog noted a handful
of more T38 changes.  A particularly interesting one for me was:

2009-11-30 21:55 +0000 [r231694]  Kevin P. Fleming <kpfleming at
digium.com>

I was getting T38FaxMaxDatagram size miss-matches in the T38
negotiation which was causing failures, IFP byte miss-match and buffer
overflow errors.  This update has resolved these particular issues and
with my specific lab testing, T38 faxing is negotiating faster and
completing quicker.

So just to check myself, I defaulted my lab setup and rebuilt with
just basic configs on the Mediant 1000, the MP203 (behind a NAT) and
Asterisk, sent several faxes coming and going with no errors, all T38
negotiated faxes nailed up at 14400.  I'll be doing a lot more testing
next week, but I'm very happy with the results so far.

I wanted to share so you all were aware of the progress that is being
made in this particular area and also thank the dev team for
responding to the bug tracker, taking suggestions for improvements and
doing the coding to make Asterisk the best it can be.  I can't wait
for T38 gateway.  Keep up the good work.

Thanks.

JR
-- 
JR Richardson
Engineering for the Masses