Kerberos is available in many forms. In this Network Design Manual, we relate our ongoing experiences with the Kerberos protocol in our Syracuse University labs. Although some organizations still rely on Kerberos 4, all examples and notation in this manual refer to Kerberos 5. This version includes several modifications, such as cross-realm authentication, forwardable tickets, and internal security enhancements, that make it the best choice for new installations. This is simple verification of a user's identity.
File permissions are a good example of access controls.
This is usually the most complex aspect of network security since it requires the secure, centralized storage and access of these ACLs. Authorization can occur only once a user is authenticated, as authorization systems rely on lists of authenticated users. The basic task of recording who accessed what resource. Most network operating systems and services include some form of logging. This can either be performed independently at each service, or through a centralized accounting server.