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Lync 2013 No Ringback tone - Any way to suppress 183 SDP ?

    Question

  • Hi,

    I'm using a non Microsoft approved sip trunk and managed to sort out everything except that there is no ring back tone for calls from PSTN to Lync. I understand that it is because of the 183 SDP that Lync sends after 180 ringing which makes the SBC look for ring-back media within 183. But as everyone knows, that doesn't happen with Lync. :)

    I've read that if SBC suppresses PRACK message or the 183 SDP post 180 ringing, then ring back might be possible.

    Is there anyway I can achieve this using / from Lync itself ? I tried one of the OCS R2 ringing scripts which sends a false 180 ringing, but that doesn't help.

    Thanks in advance,


    Murali Krishnan| My blogs: UnifiedMe | Twitter: @Mkris9

    Wednesday, July 24, 2013 7:51 AM

Answers

  • Hi Murali,

    Unfortunately, there is no way to do this within Lync when using a Direct SIP trunk integration. 

     Lync is expecting the SIP trunk to provide the ringback tone, until RTP media arrives. If SIP trunk gets SDP in 183 but no RTP traffic and stop playing ringback tone, then you'll get the issue you are describing. Either use a certified SIP trunk provider, ask them to suppress SDP from 183 messages originated by Lync, or insert a qualified SBC in order to supress the SIP message.


    Please “Vote As Helpful” and/or “Mark As Answer” if this post helped you. Thanks!
    Adam Curry, UC Consultant, Unify Square Inc. (Blog, Twitter)
    Looking for Lync Users Groups in your area? Check out Lync Users Group

    Wednesday, July 24, 2013 6:03 PM

All replies

  • Hi Murali,

    Unfortunately, there is no way to do this within Lync when using a Direct SIP trunk integration. 

     Lync is expecting the SIP trunk to provide the ringback tone, until RTP media arrives. If SIP trunk gets SDP in 183 but no RTP traffic and stop playing ringback tone, then you'll get the issue you are describing. Either use a certified SIP trunk provider, ask them to suppress SDP from 183 messages originated by Lync, or insert a qualified SBC in order to supress the SIP message.


    Please “Vote As Helpful” and/or “Mark As Answer” if this post helped you. Thanks!
    Adam Curry, UC Consultant, Unify Square Inc. (Blog, Twitter)
    Looking for Lync Users Groups in your area? Check out Lync Users Group

    Wednesday, July 24, 2013 6:03 PM
  • Agree with Adam, you may ask for SIP trunk provider to supress SDP or use a certified SIP trunk

    provider.

     


    Kent Huang
    TechNet Community Support

    Friday, July 26, 2013 5:05 AM