What feature provided at the Windows Server 2012 domain functional level creates a secure channel or tunnel between a client seeking authentication for a computer service and the server providing secure access keys for secure communications.

The correct answer to the following question will be "Flexible Authentication Secure Tunneling".

Explanation:

FAST seems to be a member of the Kerberos Pre-authentication system.

It offers a secure connection between both the customer as well as the KDC (Key Distribution Center), and therefore can also supply key content used only to validate the secured network answer key. This functionality made available at the logical level of the Windows 2012 framework provides a safe communications channel.