The first networks were time-sharing networks that used mainframes and attached terminals. Such environments were implemented by both IBM’s System Network Architecture (SNA) and Digital’s network architecture. Local area networks (LANs) evolved around the PC revolution and provide high-speed, fault-tolerant data networks that cover a relatively small geographic area or that is confined to a single building or group of buildings. They provide connected users with shared access to devices and applications and allow them to exchange files and communicate via electronic mail. Wide area networks (WANs) cover broader geographic areas, often using transmission facilities provided by common carriers, such as telephone companies, to interconnect a number of LANs.

Whilst LANs and WANs make up the majority of networks – indeed, the Internet can be correctly regarded as the largest WAN in existence – there are many different types of network, categorized by a number of distinguishing characteristics:

  • topology: the geometric arrangement of a computer system. Common topologies include a bus, star, and ring
  • standards/protocols: definitions of common sets of rules and signals that specify how computers on a network communicate.Ethernet and Token Ring are examples of network cabling standards, whilst TCP/IP is the predominant network communications protocol
  • architecture: networks can be broadly classified as using either a peer-to-peer or client-server architecture.

In addition to the computers themselves, sometimes referred to as nodes, the implementation of a network involves:

  • a device on each connected computer that enables it to communicate with the network, usually called a network interface card (NIC)
  • various items of specialist network hardware, including devices to act as connection points between the various nodes, generally referred to as hubs or switches
  • a connection medium, usually a wire or cable, although wireless communication between networked computers is increasingly common.

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