IAS error code 96 and 97

[Michael Chau]

I am using windows server 2000 with IAS installed.
Using PEAP as protocol, AD user login name and password.

I have got two error codes for the failed authentication

CODE 96:
Access request for user HKRI\michael.chau was discarded.
Fully-Qualified-User-Name = <undetermined>
NAS-IP-Address = <not present>
NAS-Identifier = ESW-0124
Called-Station-Identifier = <not present>
Calling-Station-Identifier = <not present>
Client-Friendly-Name = Zyxel
Client-IP-Address = 172.18.252.62
NAS-Port-Type = <not present>
NAS-Port = <not present>
Reason-Code = 96
Reason = The authentication request was dropped because the session timed
out.

CODE 97
Access request for user HKRI\michael.chau was discarded.
Fully-Qualified-User-Name = <undetermined>
NAS-IP-Address = <not present>
NAS-Identifier = ESW-0124
Called-Station-Identifier = <not present>
Calling-Station-Identifier = <not present>
Client-Friendly-Name = Zyxel
Client-IP-Address = 172.18.252.62
NAS-Port-Type = <not present>
NAS-Port = <not present>
Reason-Code = 97
Reason = The authentication request was dropped because it contained an
unexpected packet.


Any idea