Radius - HP MSR Series Configuration Manual

RADIUS

Remote Authentication Dial-In User Service (RADIUS) is a distributed information interaction
protocol that uses a client/server model. The protocol can protect networks against unauthorized
access and is often used in network environments that require both high security and remote user
access.
The RADIUS authorization process is combined with the RADIUS authentication process, and user
authorization information is piggybacked in authentication responses. RADIUS uses UDP port 1812
for authentication and UDP port 1813 for accounting.
RADIUS was originally designed for dial-in user access, and has been extended to support
additional access methods, such as Ethernet and ADSL.
Client/server model
The RADIUS client runs on the NASs located throughout the network. It passes user information to
RADIUS servers and acts on the responses to, for example, reject or accept user access requests.
The RADIUS server runs on the computer or workstation at the network center and maintains
information related to user authentication and network service access.
The RADIUS server operates using the following process:
1. Receives authentication, authorization, and accounting requests from RADIUS clients.
2. Performs user authentication, authorization, or accounting.
3. Returns user access control information (for example, rejecting or accepting the user access
request) to the clients.
The RADIUS server can also act as the client of another RADIUS server to provide authentication
proxy services.
The RADIUS server maintains the following databases:
•
Users—Stores user information, such as the usernames, passwords, applied protocols, and IP
addresses.
•
Clients—Stores information about RADIUS clients, such as shared keys and IP addresses.
•
Dictionary—Stores RADIUS protocol attributes and their values.
Figure 2 RADIUS server databases
Information exchange security mechanism
The RADIUS client and server exchange information between them with the help of shared keys,
which are preconfigured on the client and server. A RADIUS packet has a 16-byte field called
Authenticator. This field includes a signature generated by using the MD5 algorithm, the shared key,
and some other information. The receiver of the packet verifies the signature and accepts the packet
only when the signature is correct. This mechanism ensures the security of information exchanged
between the RADIUS client and server.
The shared keys are also used to encrypt user passwords that are included in RADIUS packets.
User authentication methods
The RADIUS server supports multiple user authentication methods, such as PAP, CHAP, and EAP.
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