Posted in AudioCodes, Lync Server 2013, Skype for Business

AudioCodes AA – ACD call cannot transfer to any internal SfB User




  • AudioCodes Auto-Attendant is installed as virtual machine inside the SBA.
  • SBA is associated to a SfB Enterprise Edition in Central Pool.
  • AudioCodes AA configured with Automatic Call Distribution (ACD) in Call Work Flow
  • When a PSTN caller calls to AA IVR and chose ACD option (e.g. transfer to Receptionist), Receptionist answer the call but when it tries to transfer to any internal SfB user within the branch site, the transfer failed.

Errors on SfB logs captured on SBA

  • The call cannot be transferred
  • SIP/2.0 504 Server time-out
  • ms-diagnostics: 1038;reason=”Failed to connect to a peer server”;ip-address=”″;peer-type=”InternalServer”;winsock-code=”10061″;winsock-info=”The peer actively refused the connection attempt”;source=”SfBPoolinCentralSiteFQDN”
  • SIP/2.0 400 Bad Request



Open TCP port 15001 from SfB servers in Central office to AudioCodes Auto-attendant.

SfB requires that all servers, that receive REFER and start a new call as result of the REFER, have access to the referring server, for authenticating the referred-by header.

In the case above all servers should have access to AudioCodesAA.local:15001


Thanks to AudioCodes R&D, they found the solution!

But this port is not on Firewall requirement on AC document so we have requested it to be added.




Posted in AudioCodes, ShoreTel

Incoming call disconnects after 32 seconds!!!


  • Inbound: Optus -> SBC -> ShoreTel
  • Incoming call from Optus to Shoretel drops after 32 seconds


  • Optus -> SBC -> ShoreTel


As you can see on the SIP ladder diagram above, there’s unusual multiple 200 OK response from ShoreTel.

Solution: Unfortunately, the solution wasn’t shared by ShoreTel engineers, however the fixed was done on their end. So the next time you see above trace within SBC, immediately asks assistance from ShoreTel engineer to address the issue on their end.


Posted in AudioCodes, ShoreTel

488 Not Acceptable Here

Happy New Year!

After spending a vacation for Christmas, I had my first AudioCodes virtual SBC implementation for this year and the error above took me a while to resolve. A while means few hours, thank God not days 🙂

So here’s the scenario.

ShoreTel -> SBC -> Optus

Essentially, the error above only happens to few outbound numbers. Almost all other numbers are working fine. Diagram below shows where the 488 Not Acceptable Here error comes from.


Based on the error, when Optus is sending a valid 180 Ringing to SBC, for some reason the SBC automatically sending “488 Not Acceptable Here” error to ShoreTel thus call is not able to connect successfully.

Solution: On the SBC’s IP Profile for ShoreTel leg, you have to disable “Early Media”. Search for parameter IpProfile_EnableEarlyMedia.

Note: When EarlyMedia is enabled, the device sends a SIP 18x response with SDP, allowing the media stream to be established before the call is answered. However, on above case the SBC doesn’t have Media channels and DSP resources on Feature Key license that’s why it can’t construct the SIP 18x response with SDP. So the only option is to disable it.