NIS+ is a new version of the network information nameservice from Sun. The biggest difference between NIS and NIS+ is that NIS+ has support for data encryption and authentication over secure RPC.
The naming model of NIS+ is based upon a tree structure. Each node in the tree corresponds to an NIS+ object, from which we have six types: directory, entry, group, link, table and private.
The NIS+ directory that forms the root of the NIS+ namespace is called the root directory. There are two special NIS+ directories: org_dir and groups_dir. The org_dir directory consists of all administration tables, such as passwd, hosts, and mail_aliases. The groups_dir directory consists of NIS+ group objects which are used for access control. The collection of org_dir, groups_dir and their parent directory is referred to as an NIS+ domain.