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Intermittent one-way audio and dropped calls

    Question

  • We are having intermittent one-way audio problems with in-bound and out-bound calls, as well as some dropped calls. This is happening with regular two party calls as well as conference calls. We are using three different SIP providers providing native Lync SIP (i.e., no gatways, SBC, or PBX). The problem appears to be happening with all three SIP providers. We are running all components of Lync on their own servers and do not see any memory or CPU issues. We peak around 250 simultaneous callers but our internet connection is far from saturated. We've experienced the problem with only 20 current calls active. We applied the very latest patches from Microsoft, but still have the problem. Our network is all newer Cisco equipment with up-to-date firmware.

    We have to assume the problem is internal and likely something with our network or configuration. We've had three different Lync experts in but they could find nothing.

    I'm open to any suggestions.

    Thank


    Friday, August 26, 2011 11:59 AM

Answers

  • Kevin,

     

    Is your mediation Server collocated on Front End Server ?

    If yes please check if you have defined a PSTN IP Address on the Front End Server properties.

     

    Check the trunck configuration Get-CsTrunkConfiguration

    If RTCPActiveCalls is set to True, the Mediation Server or Lync Server client can terminate a call if it does not receive RTCP packets for a period exceeding 30 seconds.

    Try setting it to false.

    http://technet.microsoft.com/en-us/library/gg398238.aspx 

     

    Also check if MediaBypass EnableBypass is true on the trunck

    Try disabling it if it is enabled.

     

    -Santosh

     

     

     

     

     


    Microsoft Unified Communications Team
    Sunday, August 28, 2011 5:15 PM
  • The problem has been resolved.  It was an issue in our SIP Trunk provider's NOC.  They had a configuration issue that was sporatically dropping packets.
    • Marked as answer by KevinTLutz65 Monday, September 12, 2011 5:07 PM
    Monday, September 12, 2011 5:07 PM

All replies

  • One way audio is a good sign that you should make sure your firewall is not doing funny stuff with SIP. Check your firewall.

    All all SIP trunks coming into one location?


    http://windowspbx.blogspot.com
    Friday, August 26, 2011 5:32 PM
  • Yes, all SIP Trunks are coming into our main location. The Internet connection is 20MB fiber point-to-point with the provider's NOC and is provided by one of the SIP Trunk providers.
    Friday, August 26, 2011 6:42 PM
  • Kevin,

     

    Is your mediation Server collocated on Front End Server ?

    If yes please check if you have defined a PSTN IP Address on the Front End Server properties.

     

    Check the trunck configuration Get-CsTrunkConfiguration

    If RTCPActiveCalls is set to True, the Mediation Server or Lync Server client can terminate a call if it does not receive RTCP packets for a period exceeding 30 seconds.

    Try setting it to false.

    http://technet.microsoft.com/en-us/library/gg398238.aspx 

     

    Also check if MediaBypass EnableBypass is true on the trunck

    Try disabling it if it is enabled.

     

    -Santosh

     

     

     

     

     


    Microsoft Unified Communications Team
    Sunday, August 28, 2011 5:15 PM
  • The mediation and front end servers are two separate phycial machines.  On the mediation server we defined the PSTN IP and local network IP addresses explicitly.

    We have two mediation servers.  One handling two different SIP providers (Global Crossing and EtherSpeak) and the other handling a second, but different Global Crossing trunk.

    Our intermittent one-way audio issue has been occuring for months, but didn't become a major issue until recently.  A few weeks ago added the second Global Crossing trunk and mediation server.  We've been playing around with our call routing rules to try to determine if the problem is related to only one SIP trunk or mediation server.  It definately is happening with the mediation server running the two SIP trunks and is occurring with both providers. We are still testing to see if it happens with the second mediation server running only one SIP trunk.

    We are thinking about spinning up a third mediation severs to separate the two SIP trunks running on the one mediation server. This may help us determine if its related to the two SIP trunks on the one mediation server.

    Monday, August 29, 2011 12:34 PM
  • The problem has been resolved.  It was an issue in our SIP Trunk provider's NOC.  They had a configuration issue that was sporatically dropping packets.
    • Marked as answer by KevinTLutz65 Monday, September 12, 2011 5:07 PM
    Monday, September 12, 2011 5:07 PM
  • Just curious who the SIP provider was and if you have additional details on the resolution? We are having a similar issue with Lync 2013 where randomly we have PSTN audio dropping one way. It always seems to be the incoming audio from the PSTN side. The PSTN caller can hear the Lync caller fine but the audio is silent on the Lync side.

    If you found this post helpful, please give it a "Helpful" vote. If it answered your question, remember to mark it as an "Answer".

    Friday, June 07, 2013 2:47 PM
  • The issues that we were having were resolved soon after my original post. We have been using Lync successfully for the past two years with hundreds of users and millions of minutes. When we have occasionally had issues, they were traced back to our ISP making changes/upgrades to firewalls that blocked VOIP traffic or VOIP signaling.

    We are using Level 3 and iEtherSpeak.com for our SIP trunks with great success. The great benefit of using a SIP Truck is that you do not need any expensive gateway equipment or licensing. It makes the installation and support easier and less expensive.

    Friday, June 07, 2013 3:28 PM