In the event a secure Session Initiation Protocol (SIP) connection fails, the connection must be restricted from resorting to the unencrypted HTTP.

Prevents from HTTP being used for SIP connection in case TLS or TCP fail.

Verify the policy value for Computer Configuration -> Administrative Templates -> Skype for Business 2016 -> Microsoft Lync Feature Policies "Disable HTTP fallback for SIP connection" is set to "Enabled".

Procedure: Use the Windows Registry Editor to navigate to the following key:

HKLM\Software\Policies\Microsoft\office\16.0\lync

Criteria: If the value disablehttpconnect is REG_DWORD = 1, this is not a finding.

Set the policy value for Computer Configuration -> Administrative Templates -> Skype for Business 2016 -> Microsoft Lync Feature Policies "Disable HTTP fallback for SIP connection" to "Enabled".