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  1. FreeSWITCH
  2. FS-9855

Refused T38 reinvite on b-leg breaks T38 negotiation on a-leg when using T38 gateway mode

    Details

    • Type: Task
    • Status: Resolved
    • Priority: Minor
    • Resolution: Fixed
    • Affects Version/s: 1.6.13
    • Fix Version/s: None
    • Component/s: mod_spandsp
    • Labels:
      None
    • Environment:
      Debian+Docker
    • CPU Architecture:
      x86-64
    • Kernel:
      Linux
    • Userland:
      GNU/Linux
    • Distribution:
      Debian
    • Distribution Version:
      Debian 8 jessie
    • Compiler:
      gcc
    • FreeSWITCH GIT Revision:
      FreeSWITCH Version 1.6.13+git~20161214T213702Z~d422498d0f~64bit (git d422498 2016-12-14 21:37:02Z 64bit)
    • GIT Master Revision hash::
      n/a
    • FSS Support Agreement Customer Number and Company name:
      Telnyx LLC

      Description

      The issue occurs when sending OB Fax calls with this call flow:

      T38 device -> FS -> PSTN vendor

      The dialplan contains the following t38 related lines:

      <action application="set" data="fax_enable_t38=true"/>
      <action application="set" data="fax_enable_t38_request=true"/>
      <action application="bridge" data="{local_var_clobber=true,refuse_t38=true,execute_on_answer='t38_gateway peer'}

      We send two calls with different results:

      Call #2 behavior
      The call is established with PCMU codec.
      FS sends a T38 reinvite to the caller on the a-leg and the fax is transmitted successfully with T38 on the a-leg and PCMU on the b-leg

      Call #1 behavior
      The call is established with PCMU codec.
      FS sends a T38 reinvite to the caller on the a-leg.
      The PSTN vendor sends a T38 reinvite on the b-leg, FS refuses it with code 488 and the vendor ACKs it, keeps the call active and the RTP stream open still sending FAX tones.
       The t38 negotiation on the a-leg fails and the fax transmission fails.

      I'm attaching FS logs and traces (signaling and RTP) for both calls.

        Attachments

        1. call1.log
          56 kB
        2. call1-aleg.pcapng
          27 kB
        3. call1-bleg.pcap
          1.00 MB
        4. call2.log
          52 kB
        5. call2-aleg.pcapng
          119 kB
        6. call2-bleg.pcap
          901 kB

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              • Assignee:
                brian@freeswitch.org Brian West
                Reporter:
                rogelio.telnyx Rogelio Perez
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                Dates

                • Created:
                  Updated:
                  Resolved: