ZyXEL Communications ZyAIR G-3000H, User Manual

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G-3000H User’s Guide
Appendix G Wireless LANs 249
• Access-Challenge
Sent by a RADIUS server requesting more information in order to allow access. The
access point sends a proper response from the user and then sends another Access-
Request message.
The following types of RADIUS messages are exchanged between the access point and the
RADIUS server for user accounting:
• Accounting-Request
Sent by the access point requesting accounting.
• Accounting-Response
Sent by the RADIUS server to indicate that it has started or stopped accounting.
In order to ensure network security, the access point and the RADIUS server use a shared
secret key, which is a password, they both know. The key is not sent over the network. In
addition to the shared key, password information exchanged is also encrypted to protect the
network from unauthorized access.
Types of Authentication
This appendix discusses some popular authentication types: EAP-MD5 , EAP-TLS , EAP-
TTLS , PEAP and LEAP .
The type of authentication you use depends on the RADIUS server or the AP. Consult your
network administrator for more information.
EAP-MD5 (Message-Digest Algorithm 5)
MD5 authentication is the simplest one-way authentication method. The authentication server
sends a challenge to the wireless station. The wireless station ‘proves’ that it knows the
password by encrypting the password with the challenge and sends back the information.
Password is not sent in plain text.
However, MD5 authentication has some weaknesses. Since the authentication server needs to
get the plaintext passwords, the passwords must be stored. Thus someone other than the
authentication server may access the password file. In addition, it is possible to impersonate an
authentication server as MD5 authentication method does not perform mutual authentication.
Finally, MD5 authentication method does not support data encryption with dynamic session
key. You must configure WEP encryption keys for data encryption.