In the mid 1980s, Sun Microsystems developed a series of network protocols?Remote Procedure Call (RPC), the Network Information System (NIS), and the Network Filesystem (NFS)?that let a network of workstations operate as if they were a single computer system. RPC, NIS, and NFS were largely responsible for Sun's success as a computer manufacturer: they made it possible for every computer user at an organization to enjoy the power and freedom of an individual, dedicated computer system, while reaping the benefits of using a system with a shared filesystem that was centrally administered.
 NIS was previously known as Yellow Pages, or YP. Sun stopped using the name Yellow Pages when the company discovered that the name was a trademark of British Telecom in Great Britain. Nevertheless, the commands continue to start with the letters "yp".
Sun was not the first company to develop either a network-based operating system or a distributed filesystem, nor was Sun's approach technically the most sophisticated. One of the most important features that was missing from Sun's offerings was strong security. RPC and NFS had virtually none, effectively throwing open the resources of a network of computer systems to the whims of the network's users.
Despite this failing (or perhaps, because of it), Sun's technology soon became the standard. The University of California at Berkeley developed implementations of RPC, NIS, and NFS that interoperated with Sun's. As Unix workstations became more popular, other companies, including HP, Digital, and even IBM, licensed or adopted Berkeley's software, licensed Sun's, or developed their own.
Sun developed some fixes for the security problems in RPC and NFS over time. Meanwhile, a number of other competing and complementary systems?for example, Kerberos and DCE?were developed for solving many of the same problems.