Understanding ISA’s different Authentication types.
It is important to understand the types of authentication that ISA can use to validate with other servers and applications. This tutorial will outline the authentication methods, but will not focus on the configuration of each. Look out for other tutorials in my section on the configuration side of Authentication. Please note that all of the tests are performed using IE5.5 browsers and above, some browsers do not support other authentication types other than basic authentication.
Client certificates and server certificates
Please note: Client certificates should be installed in the web proxy service certificate store on the ISA server computer where the requests from the clients are sent to. In an array this can be one machine or multiple machines depending on the configuration for that organization. Certificates should also be mapped to user accounts.
Note: This method of Authentication will only function in windows 2000 domains.
Please Note: Using an IE browser later that 5.5 would be strongly recommended when dabbling with this type of authentication. Using other lower versions or browsers might result in no access to the resource.
Summary: I have collated and summarized allot of authentication information and hope this will help you in your quest. It is difficult to troubleshoot a problem when you are not sure of how the browser or application is authenticating. Hopefully this information will help you in you quest.