NIS+ expands the network name service provided by NIS. With NIS+, you can store information about workstation addresses, security information, mail information, Ethernet interfaces, and network services in central locations where all workstations on a network can access it. This configuration of network information is referred to as the NIS+ namespace.
The NIS+ namespace is hierarchical and is similar in structure to a traditional UNIX directory file system. The hierarchical structure allows an NIS+ namespace to be configured to conform to the logical hierarchy of an organization. The layout of information in the namespace is unrelated to its physical arrangement. Therefore, an NIS+ namespace can be divided into multiple domains, each of which can be administered autonomously. Clients may have access to information in other domains as well as their own if they have the appropriate permissions.
NIS+ uses a client-server model to store and have access to the information contained in an NIS+ namespace. Each domain is supported by a set of servers. The principal server is called the master server and the backup servers are replicas. The network information is stored in standard NIS+ tables in an internal NIS+ database. Both master and replica servers run NIS+ server software, and both maintain copies of NIS+ tables. Changes made to the NIS+ data on the master server are incrementally propagated automatically to the replicas.
NIS+ includes a security system to protect the structure of the namespace and its information. 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.