The Network Information Service Plus (NIS+) is similar to NIS but with many more features. NIS+ is not an extension of NIS. It is a new software program.
The NIS+ name service is designed to conform to the shape of the organization that installs it, wrapping itself around the bulges and corners of almost any network configuration. Unlike NIS, the NIS+ name space is dynamic because updates can occur and be put into effect at any time by any authorized user.
NIS+ enables you to store information about workstation addresses, security information, mail information, Ethernet interfaces, and network services in central locations where all workstations on a network can have access to it. This configuration of network information is referred to as the NIS+ namespace.
The NIS+ namespace is hierarchical, and is similar in structure to the UNIX directory file system. The hierarchical structure allows an NIS+ namespace to be configured to conform to the logical hierarchy of an organization. The namespace's layout of information is unrelated to its physical arrangement. Thus, an NIS+ namespace can be divided into multiple domains that can be administered autonomously. Clients may have access to information in other domains in addition to 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 called replicas. The network information is stored in 16 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 sophisticated 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. See Chapter 6, Security Overview for a more detailed description of NIS+ security, and Chapter 8, Administering NIS+ Keys for information on administering NIS+ security.