DTOO422 - In the event a secure 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.


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'.

Supportive Information

The following resource is also helpful.

This security hardening control applies to the following category of controls within NIST 800-53: System and Communications Protection.This control applies to the following type of system Windows.