Connection from Skype to Audiocodes not working after KB4540670, fixed by disabling VMQ RRS feed

  • Question

  • Hi, we have a Skype for Business installation and multiple Audiocodes Mediant 1000 gateways. Skype server is running on Windows Server 2016 on top of Hyper-V of Windows Server 2016. Host has Intel X520 NICs. VM has used VMQ, but not SR-IOV, for years without any issues.

    Yesterday we installed KB4540670 on both the Hyper-V hosts as well as the VM. Today around noon we suddenly received reports from all our locations that PSTN calls would not work. I found that Audiocodes logs were full of messages like this:

    -- SRTP Error - failed decrypting RTCP packet (PacketLength=191, PayloadLength=0): wrong SSRC (11) [Code:0x3700e] [CID:53]
    SRTCP_SSRC_ERROR:1  [Code:0x5004] [CID:53]

    And there were corresponding events in Skype log:

    An attempt to route to a gateway failed. Could not route to Gateway xxxxx, the attempt failed with response code: 503 Service Unavailable 

    Uninstalling KB4540670 from the VM or moving it to another Hyper-V host did not help anything. After reboot we probably could make one or two calls but then it stopped working.

    Eventually I disabled VMQ for that VM, and everything started to work in that very instant.

    Could there be a compatibility issue with either VMQ or the Intel drivers in KB4540670?

    Monday, March 16, 2020 4:56 PM


  • Seems that nobody else has experienced the same problem. I guess it must have been a special combination of factors that caused our issue.

    • Marked as answer by svhelden Tuesday, March 31, 2020 5:23 AM
    Tuesday, March 31, 2020 5:23 AM

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