Glossary

Todays world of communications is advancing faster all of the time. To help you understand the difference between ADSL and VoIP we have listed the defenitions of the most common terms in the telecom and internet industry today

Access Latency

Maximum time that a port will take to either successfully transmit a packet or discard it as measured from the time the packet is presented for transmission.

Access Line

The physical telecommunications circuit connecting an end-user location with the serving central office in a local network environment. Also called the local loop or "last mile." See also Local Loop.

ADSL

High speed Internet access that works over existing telephone cables. ADSL (Asynchronous Digital Subscriber Line) works by splitting the phone line into two frequency ranges. The frequencies below 4 kHz are reserved for voice, and the range above that is used for data. This is what makes it possible to use the line for phone calls and data network access at the same time. ADSL provides download speeds of up to 8Mbit/s and upload speeds of up to 1Mbits per second. The different upstream and downstream rates define the Asymmetry. Home and small business users would predominantly use this form of DSL.

Always on

Current dial-up services require the user to 'make a call' to the ISP. The connection is only active during the duration of the call. Most xDSL implementations (including ADSL and SDSL) enable the connection to be always on.

Attenuation

The decrease in the magnitude of the power of the signal transmitted over a wire (as a function of distance) measured in decibels. As distance increases, attenuation also increases and hence signal power decreases.

Bandwidth

Bandwidth is the speed at which data travels across a network connection when using the Internet for example. Normally measured in KB or MB per second. The higher the number the faster the connection.

Bandwidth on demand

Designed for organisations that require different amounts of bandwidth at different times of the day.

Bit

The smallest measurement for digital information used in computing.

BlackBerry

A brand of hand-held computer that can send and receive e-mails, browse the Internet and make phone calls.

Blog

Short for web log. A website which is normally written by one person and deals with one particular subject. Many blogs take the form of a diary or a daily current affairs bulletin.

Bluetooth

A technology allowing the transfer of information between two or more devices (such as mobile phones and laptop computers) without the need for wires. The normal range of a Bluetooth signal is around ten metres.

Browser

A software program that allows the user to look at web pages and organise files. Popular browsers include Internet Explorer, Mozilla Firefox and Apple Safari.

Burn

Slang term for ‘make’ as in ‘burning a CD or DVD’. Information is ‘burnt’ onto a removable disc such as a CD. The recording device used is often referred to as a ‘burner’.

Byte

A unit which measures the size of data file. A byte usually consists of eight ‘bits’. 1024 bytes make up a kilobyte (KB), while 1024 KB make up 1 megabyte (MB).

Chatroom

An Internet website where people can ‘chat’ to each other in real time, most commonly text-based.

Clipboard

An area of temporary storage space on a Windows computer, used for storing data which has been copied or cut from a document or file, before it is copied into another document or file.

Compression

A method that reduces the size of digital data so that it can be downloaded or stored more quickly.

Console

An electronic machine designed for a specific purpose such as playing games. Normally connected to a monitor or a television.

Contention Ratio

This describes the maximum number of users sharing the bandwidth on the connection between your local exchange and the Internet Service Provider. A customer with a contention ratio of 20:1 may have to share this bandwidth with up to 20 other users at peak loading. However this is unlikely as not all users will be using the service at the same time.

Cookies

When you visit a website, it may choose to store information about you and your activities in a small file, a cookie, which is stored on your computer. Cookies allow the website to remember you when you next visit the site.

CPE

Customer Premise Equipment. This refers to any equipment located at the customer's premises. DSL modems, bridges and routers are examples of CPE. They commonly contain login or registration information.

Desktop

The ‘virtual desk’ on a computer that represents items you would find on a real desk such as documents, folders and an address book, as well as giving access to software applications.

Dial up

A term used to refer to slower Internet Access using a phone modem. Usually, the user dials a telephone number and using the computer in order to connect to the Internet. The maximum bandwidth of a dial up connection is 56kbit/s.

Disc drive

Computer hardware that stores and recalls data on a disc. Different types of disc drive include ‘hard drives’ (built in to the computer), ‘optical drives’ (which play CDs, & DVDs) and ‘external drives’ (such as Zip drives which attach externally to a computer).

DNS

(Domain Name System) Name resolution software that lets users locate computers on a UNIX network or the internet (TCP/IP network) by domain name. The DNS server maintains a database of domain names (host names) and their corresponding IP addresses.

Domain name

The name that identifies a particular group, organisation or company. The domain name is used in web addresses and usually identifies both the name of the holder, and its type or location.

Download

To transfer a file from one computer or disk to another computer, most commonly using the Internet. It is also used to describe moving images from a phone or camera to a computer, for example.

Downstream

Data flowing from the Internet to your computer (surfing the net, getting email, downloading a file)

DSL

DSL (Digital Subscriber Line) provides high-speed Internet Access using regular telephone lines. It has the ability to move data at speeds up to 8Mb/s or eight million bits per second, or 140 times quicker than the fastest analogue modems available today.

DSLAM

A DSLAM (Digital Subscriber Line access Multiplexer) is a device located in the central office switch that enables it for xDSL capabilities.

Dynamic IP Address

An IP address that is automatically assigned to a client station in a TCP/IP network, typically by a DHCP server. Network devices that serve multiple users, such as servers and printers, are usually assigned static IP addresses. (See static IP address)

E-commerce

Short for electronic commerce, this refers to buying and selling of goods and services over the Internet.

E-mail

Short for electronic mail. A way of writing, sending and receiving messages over an electronic communication system. Also describes a message that uses this system.

Encrypt

To ‘scramble’ the data within a file so that only those who have the digital key or password can view it.

File

A collection of information that is stored within a computer system. Files can contain many different types of information, including pictures, music, documents and web pages.

Firewall

A firewall is designed to keep a network safe from intruders. It can be a single router that filters out unwanted packets or may comprise a combination of routers and servers each performing some type of firewall processing.

Folder

An electronic ‘container’ allowing you to store files - making it easier to organise the information on a computer.

Gif

Stands for Graphic Interchange Format. A Gif is a low-quality graphics file that is limited to 256 colours. Gif files are very common on websites, due to their small file size.

Gigabyte (GB)

A gigabyte (GB) is a unit that measures file sizes. 1024 megabytes (MB) make up one GB. The capacity of a hard drive is commonly measured in GB.

Hardware

The opposite of software, hardware refers to physical computer or phone equipment such as a monitor or a disc drive.

Intranet

This term is mainly used to describe an internal website – that is, one only available to people who are part of an organisation or company. In other words, it is a private Internet.

IP address

(Internet Protocol address) The address of a computer attached to a TCP/IP network. Every client and server station must have a unique IP address. Client workstations have either a permanent address or one that is dynamically set assigned to them each dial up session (see Static & Dynamic IP address for more detail) IP addresses are written as four sets of numbers separated by periods; for example, 204.171.64.2

ISDN

Short for Integrated Services Digital Network. A type of phone network system which allows faster and better quality transmission than normal phone systems.

ISP

Short for Internet Service Provider. An ISP is the name of the company who provides your broadband or dial-up Internet connection, for example British Telecom.

Java

A computer programming language which works on all computer platforms and is designed mainly to allow users to interact with web pages. It should not be confused with Javascript.

JPEG

Stands for Joint Photographic Experts Group. A JPEG is a picture file that is compressed to make the file smaller, so that it can be transmitted across the Internet more quickly.

Keyboard

Controls the operation of a computer, as well as allowing a user to type letters and numbers. The most popular type of keyboard is known as ‘QWERTY’ due to the arrangement of its letter keys.

Kilobyte (KB)

A kilobyte (KB) is a unit which measures file sizes. 1024 bytes make up one KB, while 1024 KB make up one megabyte (MB).

LAN

Local Area Network. A communications network that serves users within a confined geographical area. The "clients" are the user's workstations typically running Windows, although Mac and Linux clients are also used. The "servers" hold programs and data that are shared by the clients. Servers come in a wide range of sizes from Intel-based servers to mainframes. Printers can also be connected to the network and shared.

Laptop

A portable computer so-called as it can be used while balanced on the user’s lap. Sometimes called a notebook.

Loop Qualification Check

A test the telephone company can perform to see how far a customer is from the Central Office Switch.

Megabyte (MB)

A megabyte (MB) is a unit which measures file sizes. 1024 kilobytes (KB) makes up one megabyte (MB), while 1024 MB make up one gigabyte (GB).

Memory

Often referred to as RAM, this describes the area that a computer uses to run programs and hold data. A computer with a high amount of RAM in its memory will be able to access this information more quickly than one with a small amount.

Modem

A device allowing one computer to connect to another using a phone line. It is most often used to connect a computer to the Internet.

Monitor

An electronic device similar to a television that displays information from a computer or games console.

Mouse

A hand-controlled pointing device attached to a computer to enable the user to operate certain tasks. Its pointer onscreen is often referred to as a cursor.

MP3

A popular compressed multimedia file type used for music (audio) files, particularly for distribution over the Internet. This is the file type used by MP3 players such as Apple’s iPod.

MP4

A compressed multimedia file type used particularly for moving picture and music (audio) files.

Multimedia

This term describes something which combines data, images and sound. For example, a conference presentation containing video clips might be referred to as a ‘multimedia presentation’.

NAT

Network Address Translation. This allows an organisation to present itself to the Internet with far fewer IP addresses than there are nodes on its internal network. The NAT technology, which is typically implemented in a router, converts the private IP addresses (such as in the 10.0.0.0 range) of the node on the internal private network to one IP address or of several IP addresses for the public Internet. It changes the packet headers to the new address and keeps track of each session, so that when the packets come back from the Internet, it performs the reverse conversion to the IP address of the client machine. NAT also serves as a firewall by keeping internal addresses hidden from the outside world.

Network

A network is created when two or more computers are connected together. LAN is the most popular kind of network used within buildings and the Internet is the world's largest network.

Palmtop

A small computer designed to fit in a user’s hand. Generally used as a personal organiser but increasingly capable of sending e-mails, browsing the Internet and performing other complex tasks.

PDF

Short for Portable Document Format, a pdf is used to display a document as it is intended to be displayed, as it will look the same regardless of the type of computer it is displayed on.

Pixel

Short for Picture Element, a pixel is the smallest part of a digital image which can be displayed on a computer screen. A digital picture can consist of millions of pixels. A monitor’s screen resolution size is also measured in pixels.

Proxy server

A server that is located between two servers, usually to increase performance or security, or both. It processes tasks rather like a phone switchboard operator does, passing them to another server if it cannot process them.

PSP, PS2, PS3

Short for PlayStation Portable, PlayStation 2 or PlayStation 3. Popular games consoles made by Sony. All but the PSP can also be used to play DVDs and CDs.

Resolution

Refers to the level of detail of a screen or an image. The higher the resolution, the better picture quality.

Screensaver

Originally designed to preserve the quality of a computer monitor, a screensaver is an image or pattern appearing on screen when a computer is not being used, either for entertainment or security purposes. Not to be confused with "Desktop image", which is the background image displayed on modern graphical computer interfaces.

Scroll

Moving content within a display ‘window’ on a computer screen.

SDSL

SDSL (Symmetric DSL) is a single twisted pair line, carrying 2.3Mbit/s of data in each direction on a duplex line. The term symmetric is used in this context, as the data rate is the same in both directions.

Search engine

A search engine is Internet software which catalogues websites in a database so that computer users can look up things on the Internet. E.g. Google.

Server

A computer providing services or software to other computers within a network.

Shortcut

A file that contains a link to another file or program, or a button which performs a task when pressed. Shortcuts are usually represented by a small picture or logo.

Software

The opposite of hardware, software generally refers to computer programs and applications. Microsoft Windows is an example of software.

Spam

Spam is the electronic equivalent of junk mail – unsolicited and usually commercial e-mail messages.

Spyware

Malicious software applications which install themselves on a computer without the user’s knowledge, particularly while connected to the Internet. They then record information about the activity on that computer, or worse, let someone else take control of the computer from another location.

Static IP Address

A permanent IP address that is assigned to a node in a TCP/IP network. Servers and routers are usually assigned static IP addresses, while client stations are often assigned dynamic IP addresses from a DHCP server each time they come online (see Dynamic IP address).

Taskbar

A taskbar is a central computer application that enables the user to access and monitor programs and files quickly.

TIFF file

Short for Tagged Image File Format. A type of picture file that is of very high quality. It is often further shortened to TIF.

Toolbar

A block, or bar of buttons which perform certain tasks within a computer program when pressed.

Trojan

A malicious program that usually installs itself onto a computer without the user’s knowledge and can cause a great deal of damage. Trojans are often attached to legitimate programs received on an e-mail and, once activated, can allow other people to gain access to the files on the infected computer.

Upload

To transfer a file from one computer or disk to another computer, most commonly using the Internet. See also download.

Upstream

Data flowing from your computer to the Internet (sending emails, uploading a file).

VDSL

VDSL (Very high bandwidth DSL) is in the early development phase but promises much higher data rates over relatively short distances (between 51 and 55 Mbit/s over lines up to 1,000 feet or 300 metres in length)

Virus

A virus is a program or piece of programming code that ‘infects’ a computer without the user knowing, and can cause a wide range of problems. A constantly evolving threat, viruses are most often spread using e-mail.

Virus protector

Software which protects a computer from viruses, which can be harmful, by automatically removing them from the system. For home users, Grisoft provide program available free from their website which is a recommended safeguard against viruses that can be transferred to your computer.

VOD (Video On Demand)

The ability to activate a stored or live motion picture stream; in xDSL the application that allows subscribers to view movies or other video programming on request, similar to cable television's Pay-Per-View.

Wallpaper

Usually describes the picture used as a background for a computer’s desktop.

WAP

Short for Wireless Application Protocol. A technology allowing users to access information, e-mail and some Internet content using wireless devices such as mobile phones and pagers.

WAV file

Short for waveform. A digital sound file format, developed for Microsoft Windows, which stores audio as a waveform.

Webcam

A digital video camera attached to a computer, designed for broadcasting live or recorded pictures over the Internet.

Wireless LAN (WLAN, Wi-Fi)

A local area network that transmits over the air typically in the 2.4GHz or 5GHz unlicensed frequency band. It does not require line of sight between sender and receiver. Wireless base stations (access points) are wired to an Ethernet network and transmit a radio frequency over an area of several hundred feet through walls and other non-metal barriers. Roaming users can be handed off from one access point to another like a cellular phone system. The major wireless LAN standard today is the IEEE 802.11, more widely known by the "Wi-Fi" logo. Wireless Wi-Fi adapters (Wi-Fi transceivers) are either built into most new laptops or added via a PC card slot or USB. Wireless adapters for desktop machines can be plugged into a USB port or PCI slot.

XBOX

A popular games console made by Microsoft which has its own hard drive, as well as being able to play DVDs and CDs.

xDSL

This is a 'catch-all' phrase encompassing the family of DSL technologies (ADSL, SDSL...)

Zip

To zip a file means to compress it so that it takes up less space on a disk, particularly to allow quicker transfer over the Internet.

Zip drive

A disc drive which plays or records to a Zip disk.