Information and Communication Technology
If you are reading this, you are almost certainly already connected to the Internet, but do you know how that connection is made?
And I don't mean clicking on the connect button on your computer screen.
This page looks at the hardware and software that is involved in establishing an Internet connection, together with the types of connection that are commonly used.
If a computer is to be connected to the Internet, a device called a modem is needed. The word modem is shortened from the term modulator-
The modem is used to convert the digital signals used by the computer into ones the analogue ones used by telecommunications systems. Different modem types must be used, depending on which telecommunication system they connect to. Common ones are:
If a network is to be connected to the Internet, a router will be needed in addition to a modem. In many home and small business networks, the router and modem is combined into a single piece of equipment. In larger networks they are more usually separate devices.
The combined router and modem forms a gateway.
Finally, the modem must be connected to the Internet by a communications link.
In many cases this will be a telephone cable, either copper cable or fibre optic, which goes to the local telephone exchange and then on to an ISP.
WiFi and mobile phone systems have a radio link from the modem, which will link to an access point. From there, the communications link will normally be a copper or fibre optic cable to the ISP.
Satellite links are similar to WiFi but work over a much longer range. There is a radio link to the satellite and back down to a receiving station, from where the link will be a copper or fibre optic cable to the ISP.
The software handles the making of the connection, taking care of items such as the telephone number being dialled, the Domain Name Server (DNS) that is used and keeping track of connection times and amounts of data being transferred.
The ISP will often provide other services through the software, such as news channels, e-
In addition a browser will be needed to view the web pages on the Internet. A browser is able to read the HTML and other codes that describe a web page's contents and turn it into the page that you see, e.g. this page.
An important measurement of the quality of an Internet connection is its bandwidth.
The higher the bandwidth, the more data can be fed through the connection. Bandwidth varies according to where the connection is in the world, which ISP is used, how much the connection costs, and what equipment is used. Also, the bandwidth available when uploading to the Internet is usually only about a quarter of that available when downloading from it.
Other things being equal, the smallest bandwidth connection is dial-
DSL modems, often known as broadband modems, can offer bandwidths of 1 to 10Mb/s, many times faster than dial-
Cable modems offer even more, with a theoretical limit of around 30Mb/s.
Both DSL and cable modems are likely to allow larger bandwidths as the technology develops.
Satellite modems are potentially the ones with the largest bandwidth. Recent satellites (2010) have had an available bandwidth of 1Gb/s. It would be extremely expensive to dedicate a satellite to one link however. More usual bandwidths are around the same as DSL modems, 1 -
3G / 4G / mobile phone modems, often called mobile broadband vary a great deal in capability. 3G will give, on average, 1 to 2 Mb/s, 4G about 10 Mb/s. But... It all depends on where you are. How well the link works will depend on network traffic volume, weather conditions, whether you're static or moving and interference from other radio sources.
Although the 4IT0 specification lists VPN under 'connection type', it is really a construct which uses connections to establish a secure link between two or more locations. Only a few VPNs avoid using the Internet as part of that connection, so most VPNs must use the connection types explained in the previous module.
If a VPN uses the Internet to make a link, it is really a type of Wide Area Network (WAN). The difference between a VPN and a normal internet link is the level of security. VPNs use dedicated links and / or encryption to make it much more difficult to intercept and read the information being sent.
Image courtesy of Ludovic.ferre under the Creative Commons Attribution-