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DTMF Tones not always passing to PSTN Conference System RRS feed

  • Question

  • Our staff regularly is asked to join conference calls hosted by third-party conferencing providers. The DTMF tones are not always recognized through the PSTN and the codes to join the conference may have to be entered several times before they are accepted.  Some providers are much worse than other and it's almost impossible to get the DTMF tones recognized by some providers.

    Any recommendations? Are there settings to change the duration of the tones to lengthen them?

    We are not using any SBC or gateway devices. Our provider gives us a native Lync SIP Trunk.

    Thanks


    Monday, September 12, 2011 5:14 PM

Answers

  • Well the answer for your problem, its not in your local Lync Installation but on the Provider you are using.

    They are certified as SIP Trunking Providers for Microsoft? Probably not, because DTMF issues it's a common thing on VoIP Connection and one of the things tested on certification tests. 

    Of course you can make a workaround by adding a PSTN gateway or SBC to your local installation that works well with this provider and Lync. But still this should be fixed at provider site. If they say they provide a Lync connection they should be prepared for all scenarios. 

     

    • Proposed as answer by Sean_Xiao Friday, September 16, 2011 10:28 AM
    • Marked as answer by Sean_Xiao Monday, September 19, 2011 2:44 AM
    Tuesday, September 13, 2011 10:42 AM

All replies

  •  

    Do you have a single trunk? (so it is a consistent route)

    I've not seen this before, but not used a lot of external conf providers with Lync, which ones are the problem ones? be interesting to test

    (I guess I should also plug Lync as a conf bridge, but I'm sure there are reasons why you are using external providers)

    thanks

    Tom

     


    Tom Arbuthnot, Consultant Modality Systems
    Blog: Lync'd Up Blog Subscribe for updates: Email or RSS
    Twitter @tomarbuthnot
    Monday, September 12, 2011 6:24 PM
  • We have two different SIP Trunk providers.  I've noticed the problem on both trunks.  The conference provider is not ours, we use Lync as our conf bridge. The problem occurs when we dial into a conf bridge for a meeting set-up by a 3rd party.
    Monday, September 12, 2011 7:24 PM
  • Well the answer for your problem, its not in your local Lync Installation but on the Provider you are using.

    They are certified as SIP Trunking Providers for Microsoft? Probably not, because DTMF issues it's a common thing on VoIP Connection and one of the things tested on certification tests. 

    Of course you can make a workaround by adding a PSTN gateway or SBC to your local installation that works well with this provider and Lync. But still this should be fixed at provider site. If they say they provide a Lync connection they should be prepared for all scenarios. 

     

    • Proposed as answer by Sean_Xiao Friday, September 16, 2011 10:28 AM
    • Marked as answer by Sean_Xiao Monday, September 19, 2011 2:44 AM
    Tuesday, September 13, 2011 10:42 AM
  • We selected two different providers and both are listed on Microsoft's website as having passed the "Unified Communications Open Interoperability Program".  Nevertheless, I will follow-up with our provider.

    Thanks

    Tuesday, September 13, 2011 12:31 PM
  • Kevin,

     

    I'm not Microsoft Engineer, I only give my humble opinion of your problem from the technical side and from my experience with interoperability of Lync and other systems. But if the provider have the UCOIP Certification this kind of issues should not happen.

     

    The DTMF Method of Lync Server is very basic, only RFC2833 method it's supported, so you don't have options on Lync side to change regarding DTMF. And the sending of DTMF it's quite weird too. For a single DTMF Digit I've seen 12 packets ( too many re-transmissions ).

     

    Tuesday, September 13, 2011 12:42 PM
  • I have had similar problems.

    Easy and quick way to determine where could be an issue is to call that third-party conferencing number from mobile/fixed line and not Lync.
    If DTMF tones recognition works fine, problem is most likely on SIP Trunk provider side.
    If DTMF fails, it's third-party conferencing provider network.

    PnP
    Tuesday, September 13, 2011 1:03 PM
  • That's how we knew we had a problem. Users were contacting us saying they were attempting to dial into 3rd party conference providers from Lync (client, desk phones or speaker phones) and could not get the DTMF tones recognized. Since they had to get on the call, they picked up their cell phones and connected without a problem.

    PnP, did you find a solution to the problem?

    Tuesday, September 13, 2011 1:10 PM
  • Yes, I raised a ticket with our SIP Trunk provider (originating and terminating numbers, calls date and time)
    They got it sorted with their partner in given country (terminating number).

    Nothing you can do about this problem on Lync side.
    Tuesday, September 13, 2011 1:23 PM
  • Well the answer for your problem, its not in your local Lync Installation but on the Provider you are using.

    They are certified as SIP Trunking Providers for Microsoft? Probably not, because DTMF issues it's a common thing on VoIP Connection and one of the things tested on certification tests. 

    Of course you can make a workaround by adding a PSTN gateway or SBC to your local installation that works well with this provider and Lync. But still this should be fixed at provider site. If they say they provide a Lync connection they should be prepared for all scenarios. 

    This is a Microsoft Lync issue and needs to be resolved:

    http://support.microsoft.com/default.aspx?scid=kb;en-us;2254369&sd=rss&spid=12605

    Thursday, April 5, 2012 3:57 AM

  • Does anyone know if and when Microsoft will support DTMF relay from conference call that is hosted by Audio Video Multipoint Conferencing Unit (AVMCU) using Microsoft Lync Server 2010? This is a must-have feature to enable Lync as voice telephony system.

    "The AVMCU feature in Lync 2010 or Office Communications Server does not support DTMF relay."
    http://support.microsoft.com/default.aspx?scid=kb;en-us;2254369&sd=rss&spid=12605

    Today the only option is to ask our users to start new peer-to-peer call from Lync client (where DTMF is supported) and merge this call into a current Lync audio conferencing. That is not user friendly. I would appreciate any feedback about this topic.

    Thursday, May 10, 2012 9:14 PM