Design Considerations for Active Directory Authentication and Trusts
Authentication and trusts are integral parts of Active Directory. Before you implement any Active Directory design or try to modify your existing Active Directory infrastructure, you should have a firm understanding of how both authentication and trusts work in an Active Directory environment.
Universal Groups and Authentication
When a user logs on to a domain, Active Directory looks up information about the groups of which the user is a member to generate a security token for the user. The security token is needed as part of the normal authentication process and is used whenever a user accesses resources on the network.