asterisk users - Jun 2017 - Asterisk 1.6.2 how to debug T.38 udptl problems

Hi all

I know, a fairly old asterisk installation.

Is there any way to debug T.38 handshaking issues?

We have a C3 Voice Switch with link to the Asterisk server.

I see this Dialogue:

C3 => Asterisk
=> Invite g711
<= 200OK

C3 detects Fax and send re-invite

=> Invite T.38
Version:0
RateManagement:transferredTCF
MaxDatagram:512

So, this is only a very basic invite.

The Asterisk picks that up and replies with details:

<= 200 OK + SDP T.38

Version:0
BaxBitRate:14400
RateManagement:transferredTCF
MAxDatagramm:1400
UdpEC:t38UDPFEC

The C3 Switch then compares this whith it's capabilities and answers
with one more re-invite:

=> Invite + SDP T.38

Version:0
RateManagement:trasferredTCF
UdpEC:t38UDPFEC
MaxBitRate:14400
MaxDatagramm:512

Well so the C3 just tells the asterisk, that it only support 512 byte
datagramm, but everything else is the same.

The Asterisk replies to this invite with:

488 Not acceptable here.

Now I would like to find out what is not acceptable for the asterisk.

core set verbose 99 and debug 99 does not show any futher information.
udptl set debug on neither.

Any other way to debug the T.38 handshake?

Or does anyone have an idea over what the asterisk is stumbling?

-- 
-Beno?t Panizzon-
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On Thu, Jun 15, 2017 at 12:11:36PM +0200, Benoit Panizzon
wrote:
> Or does anyone have an idea over what the asterisk is stumbling?
What if you set the maxdata in asterisk to a value lower than the other
side? e.g. sip.conf: 
t38pt_udptl = yes,fec,maxdatagram=400