I noticed recently on several client troubleshooting (using the Snooper tool) on a particular “400 Bad Request” message that appears on the end calls.
After several cumulative updates (CU) history regression testing, I found that this behaviour started appearing with the latest two CU (or correctly, the security updates):
- KB3055014 – security update for Microsoft Lync 2013 (Skype for Business): August 11, 2015
- KB3085500 – security update for Microsoft Lync 2013 (Skype for Business): September 8, 2015
If you have any of those updates, you will find the 400 error message on every call (PSTN or Skype) when the called party disconnects. Here’s an example of the same call I made to a PSTN number:
- Until the July 2015 update, the client will send an “error” report in xml format for the front-end server
- After the August/September 2015 updates the same report is now different (similar response as a Skype-to-Skype)
There’s a <progressReport/> ending without any initial <progressReport>
- The server detects this incorrect xml format and that’s why you see the “400 Bad request” and a “Client.BadCall” fault
For the end-user there is no visible or functional impact.
I still don’t know if there are any impacts for the backend services. The call diagnostics for CDR and QoE diagnostics are correctly sent on another SIP message.