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DTMF capabilities and conversion options RRS feed

  • Question

  • Hello,

    I will get a SBC interconnect (SIP trunk) against one OCS or Lync server. The SBC will be sending INBAND DTMF (encoded in the voice - not RFC2833) for some calls and SIP INFO DTMF for other calls, both through the same trunk.

    I would like to know if the Lync server can receive both DTMF strategies for a same trunk, and conveys those DTMF to its IVR and IP phones/ATA/softphones (whatever) using one DTMF strategy (either INBAND, SIP INFO, or RFC2833) ?

    Could Lync be configured to send only one type of DTMF to the SBC (INBAND or SIP INFO), despite what it receives?

    Thanks in advance.

    Thursday, February 3, 2011 2:11 PM

All replies

  • Lync insists on RFC2833 for DTMF - I am sure that it will deny calls if this codec is not announced in SDP.
    Johann Deutinger | MCTS Exchange 2007/2010 / OCS 2007 | ucblog.deutinger.de
    Thursday, February 3, 2011 4:46 PM
  • Thank you for your answer. I am a little bit surprised to read that Lync can only do RFC2833...
    I believe that if one side does not advertise RFC2833 in the SDP, the call should still go through, but of course without the possibilities to do DTMF (if Lync can only do one type). Lync denying calls if this codec is not announced is even more surprising. :)

    Do you know if there is any documentation available which would describe more in detail the DTMF behavior?

    Tuesday, February 8, 2011 3:05 PM
  • Gateway and SIP-trunking vendors can join the UC Open Interoperability Program. They will get all specs and requirements there and will be published with their solutions after passing qualification testing: http://technet.microsoft.com/en-us/lync/gg131938.aspx

    It's not an easy way - I have gone it for OCS, OCS R2 and Lync :-)


    Johann Deutinger | MCTS Exchange 2007/2010 / OCS 2007 | ucblog.deutinger.de
    Tuesday, February 8, 2011 3:09 PM