3Com Switch 7750 Configuration Guide Guide

Overview 493
Figure 129 The AAA implementation procedure for a telnet user
The basic message exchange procedure is as follows:
1 A user requests access to the switch; the TACACS client sends an authentication
start request packet to TACACS server upon receipt of the request.
2 The TACACS server sends back an authentication response requesting for the
username; the TACACS client asks the user for the username upon receipt of the
response.
3 The TACACS client sends an authentication continuance packet carrying the
username after receiving the username from the user.
4 The TACACS server sends back an authentication response, requesting for the
password. Upon receipt of the response, the TACACS client requests the user for
the login password.
5 After receiving the login password, the TACACS client sends an authentication
continuance packet carrying the login password to the TACACS server.
6 The TACACS server sends back an authentication response indicating that the user
has passed the authentication.