Local area data networks, which are normally referred to simply as local area networks or LANs, are used to interconnect distributed communities of computer based DTE (Data Terminal Equipment) located within a single building or localised group of buildings. However, since all the equipment is located within a single establishment LANS are normally installed and maintained by the organisation. Hence they are also referred to as private data networks.

A definition of Local Area Networks that is often used is as follows:

A Local Area Network provides a system for intercommunication between computer terminals, PCs and related equipment operating within the same general area.

The initial introduction of LANS was based on the sharing of information and resources within a local work group or department. While this still continues to be the main use for LANs, it is perhaps better to regard them as a tiered system of work group networks ( intercommunication and interworking between different LANs).

LANs have a number of unique characteristics, some of which are shown below:

• Whereas WANS use nodes to separate the internal network switching from the user hosts, LAN devices omit the node computers and attach themselves directly to the network by means of a special interface - LAN devices are known as stations
• LANs are generally installed at a single site, covering only a small geographical area
• LANs usually have very high bit rates of between 1 Mbps and 20 Mbps
• LANs have a very low error rate
• LANs tend to be owned by a single organisation
• LANs most commonly use ring or bus topologies

The operation of a LAN can usually be separated into two main aspects. Firstly, the physical medium (connector types, voltage and electrical signals) and the method for placing data on the network. Secondly the operating software which establishes end-to-end transmission with guaranteed data delivery between two devices communicating across the network. It is worth noting at the outset that all LANs rely on packet-based transmission, that is, all data is "inserted" into packets whose headers carry the appropriate addressing details to identify the device with which communication is required.

Thus, in summary, the operation of a LAN can be distinguished by:

• Hardware architectures and
• Software architectures

Lastly, there is the aspect of wiring to be considered. Obviously, it can be expresses that LAN architecture is expansive in context and hence it is imperative that it is learned thoroughly.