A network operating system is software that imparts special capabilities to a computer. These capabilities revolve around the fact that the configuration of the computer with an NOS makes that computer a server (a server being a computer that can "serve up" resources to computers requesting them). The NOS, in effect, makes the server the control center for all requests made by client computers as they attempt to access resources on the LAN.
Network operating systems have changed a great deal in the last 15 years . Early NOS platforms were basically designed to supply file and print services to users. This meant that deploying other server types, such as Web servers and application servers, meant you had to place a number of single-service servers on the network.
NOS software has become much more sophisticated and now supplies multiple servicesone server might supply remote access and Web services and even serve as a router between two different IP subnets on a network. The NOS interface has also become somewhat more network administrator friendly.
For example, many of the NOS platforms now available, such as Microsoft Windows Server 2003 and Novell NetWare 6x, provide a number of additional services over and above file and print services. These services include remote access and Web site management, and also provide you with the ability to supply network services such as DHCP and DNS. The NOS utilities used to manage the servers also provide a graphical user interface (GUI) rather than a command-line format (although the command-line is still available for those who wish to use it), making it easier to configure and monitor the network.
Many NOS platforms also now provide utilities for monitoring server hardware resources and network traffic. In the past, having any decent monitoring capabilities meant you had to buy additional monitoring software. We discuss the use of these types of utilities in Chapter 19, "Network Troubleshooting".
Therefore, it is the NOS that ties computers and peripherals into a LAN by creating a server computer, which provides the communications center for the network. Let's take a closer look at how the operating system on a network client computer talks to the NOS on the network server.