One way sound for inbound calls RRS feed

  • Question

  • Hi everyone.

    I have a problem with one way sound. I have checked google didn't find any answer that fits my situation.

    I have the following setup. 

    1. On S4B site I have an SBS server that uses Asterisk as an SBC.

    2. Asterisk, that is hidden by 1:1 Nat, creates SIP trunk to Twilio to make calls to US


    1. When I'm calling to US from and S4B client, I can not hear anything, but the other part can hear me.

    2. When someone from outside is calling me, I can hear both ways.

    3. I also have an X-Lite client, that uses the same Asterisk and the same trunk to Twilio. If I call a US number form X-Lite, it works fine.

    What I have checked already:

    1. directmedia=no in sip.conf

    2. nat=force_rport,comedia in sip.conf

    3. externaddr and extern_media_address in sip.conf

    4. centralized media processing is turned on on the S4B side.

    5. media bypass is not activated on the S4B side.

    So it seems that SIP works fine, but I have a problem with RTP.

    Do you have any idea?



    Tuesday, September 27, 2016 1:37 PM

All replies

  • I would think it is a problem with your nating.

    You should check the used audio ports an that the SIP SDP information on both endpoints are correct.

    If you don't use TLS and SRTP you can use Wireshark to check at which point the audio stream works and on which point you have problems.


    regards Holger Technical Specialist UC

    Tuesday, September 27, 2016 2:46 PM
  • Hi 

    I have checked the ports. They are correct. Also I used wireshark on the SBS side to capture the traffic. And I am able to use the "Play streams" option to listen to the audio. In other words, server receives the sound correctly. 

    However, on the client side, I can not hear anything. 

    Tuesday, September 27, 2016 2:58 PM
  • Hi 

    Does anyone have any ides?

    Friday, September 30, 2016 12:26 PM
  • Hi Moiseev , 

    Did you also check with the Twilio team as well do they have some tracing to confirm as well

    Linus || Please mark posts as answers/helpful if it answers your question.

    Monday, October 3, 2016 1:56 PM
  • Hi 

    Waiting for a feedback from them. 

    Wednesday, October 5, 2016 10:07 AM
  • Hm, mediabypass is also disabled?

    If you run Wireshark on the client, could you check if the correct media port are used from the client trace?

    regards Holger Technical Specialist UC

    Wednesday, October 5, 2016 10:16 AM