The layout of information in the namespace is unrelated to its physical arrangement. Clients may have access to information in other domains as well as their own if they have the appropriate permissions. Each domain is supported by a set of servers. The principal server is called the master server and the backup servers replicas . It uses authentication and authorization to verify whether a client's request for information should be fulfilled.
Authentication determines whether the information requester is a valid user on the network.
Authorization determines whether a particular user is allowed to have or modify the information requested.