Local area networks

What is a local area network?

A local area network (LAN) is a network used for connecting a business or organization's computers to one another. With a LAN, a concept that goes back to 1970, a company's employees can:

  • Exchange information
  • Communicate
  • Access various services

A local area network usually links computers (or resources such as printers) using a wired transmission medium (most frequently twisted pairs or coaxial cables) over a circumference of about a hundred metres. For larger spaces, the network is considered to be part of a network called a MAN (metropolitan area network), in which the transmission medium is better suited to sending signals over great distances.

Hardware components of a local area network

A local area network is made of computers linked by a set of software and hardware elements. The hardware elements used for connecting computers to one another are:

  • The network card: This is a card connected to the computer's motherboard, which interfaces with the physical medium, meaning the physical lines over which the information travels.
  • The transceiver: This is used to transform the signals travelling over the physical support into logical signals that the network card can manipulate, both when sending and receiving data.
  • The socket: This is the element used to mechanically connect the network card with the physical medium.
  • The physical connection medium: This is the support (generally wired, meaning that it's in the form of a cable) used to link the computers together. The main physical support media used in local area networks are:
    • Coaxial cable
    • Twisted pair
    • Fibre optics

Local area network topologies

The hardware devices alone are not enough to create a usable local area network. It is also necessary to set a standard access method between computers, so that they know how the computers are exchanging data, especially when more than two computers are sharing the same physical support. This access method is called a logical topology. The logical topology is carried out using an access protocol. The most common access protocols are:

The way the computers are physically connected is called physical topology. The basic physical topologies are:
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