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Cisco Secure ACS 3.0 for Windows 2000/NT Servers User Guide
78-13751-01, Version 3.0
Chapter 1      Overview of Cisco Secure ACS
AAA Server Functions and Concepts
request from the AAA client should include the OTP in the username value 
(for example Fredpassword) while the password value contains an 
ASCII/PAP/ARAP password. The TACACS+ and RADIUS servers then 
verify that the token is still cached and validate the incoming password 
against either the single ASCII/PAP/ARAP or separate CHAP/ARAP 
password, depending on the user’s configuration.
The TACACS+ SENDAUTH feature enables a AAA client to authenticate 
itself to another AAA client or an end-user client via outbound 
authentication. The outbound authentication can be PAP, CHAP, or ARAP. 
With outbound authentication, the Cisco Secure ACS password is given out. 
By default, the user’s ASCII/PAP or CHAP/ARAP password is used, 
depending on how this has been configured; however, we recommend that the 
separate SENDAUTH password be configured for the user so that 
Cisco Secure ACS inbound passwords are never compromised.
If you want to use outbound passwords and maintain the highest level of security, 
we recommend that you configure users in the CiscoSecure user database with an 
outbound password that is different from the inbound password.
Password Aging
With Cisco Secure ACS you can choose whether and how you want to employ 
password aging. Control for password aging may reside either in the CiscoSecure 
user database, or in the Windows NT/2000 directory. Each password aging 
mechanism differs as to requirements and setting configurations.
The password aging feature controlled by the CiscoSecure user database enables 
you force users to change their passwords under any of the following conditions:
After a specified number of days
After a specified number of logins
The first time a new user logs in
For information on the requirements and configuration of the password aging 
feature controlled by the CiscoSecure user database, see the 
The Windows NT/2000-based password aging feature enables you to control the 
following password aging parameters:
Maximum password age in days
Minimum password age in days