Network Operating Systems
The purpose of a computer network is to allow users to share resources located on other computers, to share peripheral hardware devices such as printers and fax machines, and to communicate electronically. A network operating system (NOS) is a specialised operating system designed to provide networking functionality. The most widely used network operating systems today include Microsoft Windows Server, Novell Open Enterprise Server, and various flavours of UNIX. Most network operating systems provide the following functions:
- Creating and managing network user accounts
- Configuring and managing network resources
- Controlling access to network resources
- Providing communication services
- Monitoring and troubleshooting the network
The network operating system is deployed on network servers to enable administrators to manage network resources such as data storage areas, network printers and communication services. Because most organisations are increasingly dependent on computing services, and also partly due to the phenomenal growth of the Internet and the World Wide Web, the number of users on a typical enterprise LAN is growing almost daily. Keeping track of all these users and the resources they need is becoming increasingly difficult, time consuming and costly. One of the most important facilities provided by a network operating system, therefore, is the ability to create and manage user accounts effectively.
One of the first tasks of the network administrator will be to create a directory services structure and a network file system. The network operating system provides the required functionality. Other tasks facilitated by the network operating system include the implementation of network security policies, the optimisation of system performance, backing up and restoring data, installing and configuring distributed applications, and monitoring and managing network usage and performance. The programs used to implement the required functionality are usually part of the network operating system itself, but may be provided by third-party software vendors.
Any operating system will perform a number of basic functions. It will, for example, determine which application can use the CPU at any given time, and ensure that processor time is fairly allocated between multiple processes. It will also manage the use of main memory and secondary storage, control access to hardware, and provide a user interface. A network operating system has similar functionality, but also enables applications running on different computers to communicate with each other.
Operating systems have tended to fall into one of two categories in the past - either multi-user systems such as UNIX or Linux, or single-user desktop systems such as MS-DOS. More recently, GUI-based desktop operating systems such as Windows 95 and its descendants have increased the functionality of desktop systems to include multi-tasking (although in most respects they are still single-user systems). It could be argued that UNIX was designed from the start to support networking, while modern desktop operating systems have adapted to a networking environment.
Recent distributions of Linux (which is closely related to UNIX) can be configured as either server or desktop operating systems, and offer a choice of GUI environments. Microsoft, on the other hand, have tended to keep their network and desktop offerings distinctly separate, although some fairly sophisticated networking capabilities have been incorporated into Windows from Windows XP onwards. Nevertheless, for the necessary functionality required to configure and manage a client-server network of any size, it is necessary to employ a fully-featured and scalable network operating system. These powerful and network-oriented operating systems will be installed on network servers to provide centralised management of network resources and network security.
Appropriate software must also be installed on client computers to allow users to log on to a server and access network resources. The client software allows legitimate users of the network to authenticate themselves by providing a valid username and password. Network operating systems are defined by their ability to maintain information about all of the resources on the network, and to provide a comprehensive range of network management facilities.