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Glossary

 

 

Glossary

ADSL
Asymmetric Digital Subscriber Line. A broadband connection between a subscriber and a local telephone exchange, using the existing copper wire telephone network. ADSL is 'asymmetric' because the download speed is greater than the upload speed.

Asynchronous
Description of data where the upload and download links are running at different speeds.

Back-Up
Keeping a safe copy of information on your computer that could be lost or damaged due to human error, hardware or software failure, data corruption, theft, sabotage or natural disaster.

Bandwidth
Also known as ‘capacity’. In simple terms, how much information or traffic can be carried on the telecoms infrastructure in a given amount of time. The simple rule is that the greater the bandwidth, the easier it is to use the Internet. For example, with low bandwidth (such as a telephone dial-up connection) transferring the contents of a music CD over the Internet is difficult. With higher bandwidth (such as broadband), it is entirely feasible.

Bits per second (bps)
A ‘bit’ is a unit of electronic data. The speed of a communications link is the speed at which electronic data can be transferred and is often represented as bits per second. A 512Kbps broadband connection means up to 512 thousand bits of information per second can be transmitted.

Broadband
A high-speed telecommunications link, normally defined as allowing transmission at 512Kbps (Kilobits per second) or higher, compared to 56Kbps that is available using a dial-up modem.

Cable Modem
Cable modems are used to provide Internet access over cable TV networks and require that the networks are upgraded for two way transmission. Cable modems can offer bandwidths of up to 10Mbit/s but in the UK it is typically offered at 512Kbit/s or at 1,024bit/s. This bandwidth is shared between all users on the same segment of the cable TV network. This can lead to slower connection speeds if a number of users are active at the same time. See ‘Contention Ratio’. A Cable Modem can be added or integrated with a set-top box that provides your TV set with channels for Internet access.

Contention Ratio
With most broadband technologies, some of the bandwidth is shared between other users. For example, if the service is contended or oversubscribed at 20:1, it means that you share the bandwidth with up to 19 other users. Basic ADSL services in the UK (mainly using the BT network) typically have a contention ratio of 50:1 with the more expensive or business packages having 20:1.

DSL
A subscription to a digital Internet connection service. Provides benefits over ‘analogue’ dial-up modem technology in terms always-on connection and higher speeds of connection. See ‘xDSL’.

Firewall
Either a software application or separate piece of computer hardware that, when loaded onto a computer that has a connection to the Internet, stops unwanted visitors being able to access files on that computer. It is absolutely critical for computers or servers that have an “always on” connection to the Internet, such as ADSL or cable modem, to have an appropriate firewall application in place.

Kbps
A transmission rate of 1 Kilobits per second, where 1 Kilobit corresponds to 1,024 bits. See ‘Bits per second’.

Mbps
A transmission rate of 1 Megabit per second, where 1 Megabit = 1,048,576 bits or 1,024 Kilobits. See ‘Bits per second’.

Modem
A device that translates the digital signal from a computer into analogue signals that can travel over a standard telephone line. It can also translate the analogue signal that it receives from a telephone line in to a digital signal that a computer can recognise.

SDSL
Similar to ADSL but allows the same upload speeds as download speeds.

Service provider
The generic term for a company that provides a telecommunications service. This category includes ISPs, ASPs, Network Service Providers, Storage Network Providers, Business Service Providers, etc.

xDSL
An umbrella term for the group of dedicated subscriber line technologies which allows high-speed broadband communications over existing copper wires. The different variations include ADSL, SDSL, VDSL, UDSL, IDSL, etc.

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