The combination of computing power with high speed data communication is regarded as potentially the most powerful influence yet on our handling of information and perhaps has serious implications for society. Although in many instances computers are used to perform their intended role in a stand-alone mode, in other situations there is a need to interwork and exchange data with other computers.

Networks for computer data are one of the great success stories of the information technology industry. The use of data networks in applications such as airline reservation systems and retail banking has transformed the business operations of such geographically dispersed commercial enterprises. Indeed, many of the services that are now taken for granted would not be possible without the computer data networks which, though all pervasive, are largely invisible to the end-user.

In its simplest form, a computer data network may be defined as a number of computers and related devices interconnected by one or more transmission paths.

In the communications industry networks can be characterised into two main categories: LOCAL AREA NETWORKS and WIDE AREA NETWORKS. However, in this communications era it is apparent that users of information technology are operating a wide range of telecommunication networks, in order to achieve their business needs.

The majority of such users recognise that there is a desperate need for such systems to be able to interwork effectively and efficiently. Furthermore, users have become increasingly unhappy at the prospect of being "locked in" to any one manufacturer's range of equipment and proprietary methods of interconnecting systems. Against this background, the International Organisation for Standardisation (ISO) has drawn up universal standards for computer networks.