1.3.3 FAST
Flexible Authentication Secure Tunneling (FAST) provides a protected channel between the client and the Key Distribution Center (KDC). FAST is only available for Authentication Service (AS) and ticket-granting service (TGS) exchanges.
FAST armor uses a ticket-granting ticket (TGT) for the computer to protect Authentication Service (AS) exchanges with the KDC, so the computer’s AS exchange is not armored. The user’s TGT is used to protect its TGS exchanges with the KDC.