[asterisk-users] asterisk 13.16 / pjsip / t.38: res_pjsip_t38.c:207 t38_automatic_reject: Automatically rejecting T.38 request on channel 'PJSIP/91-00000007'

Michael Maier m1278468 at mailbox.org
Sat Jun 17 07:18:45 CDT 2017

On 06/16/2017 at 04:00 PM, Joshua Colp wrote:
> On Fri, Jun 16, 2017, at 10:49 AM, Michael Maier wrote:
> <snip>
>> t38modem and asterisk are using
>> m=image 35622 udptl t38
>>                ^^^^^
>> Provider uses
>> m=image 35622 UDPTL t38
>>                ^^^^^
>> Could this be a problem? If I'm sending internal only, it's always 
>> lowercase.
> Looking at the tests we have we only use 'udptl' as the transport.
> Without diving deep into the SDP negotiator it is possible that it gets
> upset at that, as we would only produce 'udptl'. If the SDP negotiator
> in PJSIP is case sensitive then you'd get a declined stream like you
> see. Looking at the T.38 examples from the ITU doc also shows it in
> lowercase, so uppercase is probably not commonly used.

I can proof, that UDPTL vs. udptl is the problem. After "fixing"
asterisk and opal both using UDPTL, the negotiation works flawlessly.
See attached patches.

Sending t38 faxes internally works fine. Externally via provider gets
stuck: the provider doesn't send back any t38-package to the client
(t38-packages are leaving asterisk towards the provider, but the
provider doesn't send back any package to the client :-().

Any idea what to change to get the provider to communicate?

(From the 200 Ok from the provider - nothing critical from my point of
view - these are the values I sent in the reinvite to the provider)

Connection Information (c): IN IP4
  Time Description, active time (t): 0 0
  Media Description, name and address (m): image 31410 UDPTL t38
  Media Attribute (a): sendrecv
  Media Attribute (a): T38FaxVersion:0
  Media Attribute (a): T38MaxBitRate:14400
  Media Attribute (a): T38FaxRateManagement:transferredTCF
  Media Attribute (a): T38FaxMaxDatagram:397
  Media Attribute (a): T38FaxUdpEC:t38UDPRedundancy

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