H3C S5500-SI Series, Operation Manual

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1-8
Introduction to HWTACACS
HW Terminal Access Controller Access Control System (HWTACACS) is an enhanced security protocol
based on TACACS (RFC 1492). Similar to RADIUS, it uses a client/server model for information
exchange between NAS and HWTACACS server.
HWTACACS is mainly used to provide AAA services for terminal users. In a typical HWTACACS
application, a terminal user needs to log into the device for operations, and HWTACACS authenticates,
authorizes and keeps accounting for the user. Working as the HWTACACS client, the device sends the
username and password to the HWTACACS sever for authentication. After passing authentication and
being authorized, the user can log into the device to perform operations.
Differences Between HWTACACS and RADIUS
HWTACACS and RADIUS have many common features, like implementing AAA, using a client/server
model, using shared keys for user information security and having good flexibility and extensibility.
Meanwhile, they also have differences, as listed in Table 1-3 .
Table 1-3 Primary differences between HWTACACS and RADIUS
HWTACACS RADIUS
Uses TCP, providing more reliable network
transmission.
Uses UDP, providing higher transport efficiency.
Encrypts the entire packet except for the
HWTACACS header. Encrypts only the user password field in an
authentication packet.
Protocol packets are complicated and
authorization is independent of authentication.
Authentication and authorization can be
deployed on different HWTACACS servers.
Protocol packets are simple and authorization is
combined with authentication.
Supports authorized use of configuration
commands. For example, an authenticated login
user can be authorized to configure the device.
Does not support authorized use of configuration
commands.
Basic Message Exchange Process of HWTACACS
The following takes a Telnet user as an example to describe how HWTACACS performs user
authentication, authorization, and accounting. Figure 1-6 illustrates the basic message exchange
process of HWTACACS.