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.
Description of data where the upload and download links are running at
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.
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.
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 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
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
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’.
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.
A transmission rate of 1 Kilobits per second, where 1 Kilobit corresponds
to 1,024 bits. See ‘Bits per second’.
A transmission rate of 1 Megabit per second, where 1 Megabit = 1,048,576
bits or 1,024 Kilobits. See ‘Bits per second’.
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.
Similar to ADSL but allows the same upload speeds as download speeds.
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.
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.