Network Level Authentication (NLA) completes user authentication before establishing a remote desktop connection.
Without NLA a user connects to the Terminal Server/Remote Desktop Server and the Terminal Server / Remote Desktop Server launches the Windows Login screen. This uses some resources and has the potential of DOS attacks.
The NLA uses credentials on the client to authenticate before starting the session, saving resources.
ThinManager supports NLA starting with Firmware 7.1.113 inside of the TermPack 7.1.3 package released on 6/26/2015.
Previous versions of firmware did not support NLA and required that the Allow connections only from computers running Remote Desktop with Network Level Authentication setting to be turned off.