Port 49 TACACS, Login Host Protocol

Terminal Access Controller Access Control System

TACACS is an authentication, authorization protocol that is widely used for access control on a TCP/IP network. The protocol was originally designed to be a terminal access protocol for ARPANET. TACACS allows terminal servers to forward authentication requests to a centralized database. The design was to provide a client/server protocol where clients would send an authentication /authorization request, to a Network Access Server (NAS) device which is then responds an authentication/authorization approval or denial acknowledgement.