Solaris 2.x is the next major operating system release to follow SunOS 4.x. It is expected to be as widely used in the future as SunOS 4.x is now. Solaris 2.x provides all of the Secure RPC authentication services of SunOS 4.x. In addition, Solaris 2.x provides significant enhancements to the NIS Name Service which is called NIS+ in Solaris 2.x. Like NIS, NIS+ is built upon Sun's RPC but, unlike NIS, NIS+ uses Secure RPC for name service authentication.