Computer Networks

Computer Networks

A network is two or more computers connected together to share resources and data.

A network works by splitting bits of data up into small chunks called packets. These are sent between devices along wires or wireless connections until they arrive where they are meant to go and reassembled.

There are a number of advantages of using a network, including:

  1. Being able to share hardware such as printers and scanners.
  2. Centralised (and often automatic) back-up of files.
  3. Software can be installed and updated centrally, rather than on several machines. It can also often be bought using a site licence which can save organisations money.
  4. Allows easy sharing of files.
  5. Improved communication between network users and devices.

However, there are also disadvantages of networks, for example:

  1. The equipment required such as hubs/switches and other cabling can be expensive.
  2. It will (usually) require a network manager to have oversight and maintain the system.
  3. There is a big reliance on the main server. If this goes down, people won’t be able to access their files on the server, and may not be able to communicate with one another.
  4. Connections can be slow - particularly if using the wrong set-up which leads to several data collisions.
  5. There are several security issues too:
  6. Worms and viruses can spread quickly through network connections.
  7. Hacking is also a threat, and if one connection is compromised, then they could have access to the whole network.

Wired vs Wireless Networks

When thinking about connecting a device to a network, there are two different options:

  1. Wired - makes use of a number of different types of cable to connect devices together
  2. Wireless - uses a wire-free connection such as bluetooth or wifi to connect devices together

Computer Networks, figure 1

Wired Connection

Advantages of using a wired connection are:

  1. Usually a faster and more stable connection.
  2. More secure than wireless as a would-be hacker needs physical access to a device already connected.

Disadvantages of wired connections are:

  1. Need to set up the cabling, which can mean costly building work or disruption to put the cables in.
  2. Hard to add new nodes to the network, as each will require a new connection to be added with additional cabling.
  3. Need to buy the equipment required such as hubs and switches, which are usually relatively inexpensive, but can quickly add up for larger networks.

When thinking about wired networks, we usually considered the wires within a building connected directly to the devices. These are usually ethernet cables which are then connected to a hub/switch or router.

However, there are a couple of different types of connections that are used to connect networks together. The two you need to be aware of are copper and fibre optic.

Fibre Optic connections consist of a piece of very thin flexible glass, and light signals are sent down the cable between the devices at either end. As the signal travels at the speed of light, it is a very fast connection, and due to the nature of the glass, the cables take up very little space. They also have a higher bandwidth than copper, and it is not as easy to intercept the connection between devices. However, they are a lot less flexible than metal, as the glass cannot bend as much. They are also quite expensive to install as they require specialist handling due to their fragile nature.

Copper cables on the other hand are a lot more robust than glass, and can be bent in lots of different ways. This means that they are cheaper to install. They are also able to power some devices directly without the need of a separate power source. However, copper is more expensive to buy than fibre optic cable, and is susceptible to corrosion. The signals in copper are sent using an electric current which is susceptible to interference from external sources, so the signal is likely to degrade as it travels along the wire, and it also won’t travel as fast as with a fibre optic connection.

Wireless Connection

_Advantages _of using a wireless connection are:

  1. Cheap set-up costs - one wireless access point can be used to connect a large number of devices.
  2. Nodes are not tied to a specific location.
  3. Easy to connect new devices without new hardware.

_Disadvantages _of using a wireless connection are:

  1. There can be interference on the network, particularly through walls or obstructions.
  2. Tend to be slower and less stable connections
  3. Many more security risks, as anyone is able to find the connection, and if the appropriate security features such as firewalls and authentication are not in place, people can use this connection to access all other devices on the network.
LAN, WAN or PAN?Usually owned by more than 1 person or organisation.
LAN, WAN or PAN?Covers a large geographic area.
LAN, WAN or PAN?Covers a relatively small geographic area.
LAN, WAN or PAN?Centred around an individual.
LAN, WAN or PAN?Bluetooth connection between devices up to 10m away.
LAN, WAN or PAN?The internet.

Network Types

There are lots of different types of network, but you need to know about three in particular:

  1. Wide Area Network (WAN)
  2. Local Area Network (LAN)
  3. Personal Area Network (PAN)

WAN - Wide Area Network

This covers a large geographic area and usually consist of several LANs connected together, for example across multiple office locations. They are usually owned and/or controlled by a group of people or organisations. The internet is the biggest example of a WAN.

LAN - Local Area Network

In contrast, a LAN covers a relatively small geographical area, such as an office, home or school. They are usually owned and/or controlled by a single person or organisation.

PAN - Personal Area Network

These are the smallest type of network you need to know about and they are ones centred around an individual. You only need to consider a Bluetooth connection when thinking about PANs in exams. These can allow individual devices to connect to other pieces of hardware within a 10m radius, for example, a Bluetooth connection to wireless headphones, or Airdrop facility to share files between mobile phones.