Software that (a) controls a network and its message (e.g., packet) traffic, and queues, (b) controls access by multiple users to network resources such as files, and (c) provides for certain administrative functions, including security. Note 1: A network operating system is most frequently used with local area networks and wide area networks, but could also have application to larger network systems. Note 2: The upper 5 layers of the OSI--Reference Model provide the foundation upon which many network operating systems are based.