Archive for the ‘D’ Category

Dead Zone

November 7, 2007

A dead zone is an area where wireless or mobile devices cannot work, or where they have extremely limited connectivity and hence capabilities, through lack of mobile or wireless broadband signal.

By Sarah at UK Broadband Finder
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Digital Divide

August 27, 2007

The digital divide is the gulf between those parts of the population that have access to the internet and other digital technologies, and those sections of the population that do not.

There is concern that as so many services (both commercial and governmental) become available online, groups without digital access (caused by, among other things, high cost, lack of skills, location, or a combination of these) will be left behind, and miss out on opportunities in life and in work.

By Sarah at UK Broadband Finder
Read my Broadband Glossary disclaimer

DNS – Domain Name Service

July 9, 2007

A web address is usually be made up of specific words and numbers, that are quite easy to identify and remember. However a computer communicating over the internet indentifies another using an IP address – a string of four sets of numbers between 0 and 255 with each set separated by a dot.

So when you type a web address  into your web browser, the Domain Name Service (DNS) translates the web address into the IP address so it can identify the server hosting the website you want to view. 

By Sarah at UK Broadband Finder
Read my Broadband Glossary disclaimer

Upstream / Downstream

July 5, 2007

Upstream is the direction of data traffic from your computer to the internet. Downstream is the direction of data coming from the internet to your computer.

By Sarah at UK Broadband Finder
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Download Cap

July 2, 2007

 A download cap is simply a broadband package monthly download limit. 

Broadband packages which do not offer unlimited downloads will have a fixed monthly download allowance, or cap.  This is the amount of data that can be downloaded in one month. Allowances could be anything from 2 GB to 40GB, or Unlimited (almost always including a fair use policy which means it is not truly unlimited). Aollowances are usually given in Gigs, GB, or gigabytes.

Remember that a GB download allowance refers to an amount of data, not the download speed transfer rate.

By Sarah at UK Broadband Finder
Read my Broadband Glossary disclaimer

Private DSL

June 27, 2007

With private DSL (or private ADSL)  you can link up other locations with your central office via the copper wire BT lines.

As far as the remote user is concerned, they are connected to the business network as if they were in the office. However they are not connecting with each other via the internet but via their private line. Private DSL lines are therefore more secure, as they transmit data without the risk associated with connecting via the public internet.

By Sarah at UK Broadband Finder
Read my Broadband Glossary disclaimer

DSL – Digital Subscriber Line

June 23, 2007

DSL, or Digital Subscriber Line, is a technology which allows fast transfer of data signals over copper wires between your phone and your local exchange. DSL uses high frequencies for data transfer- these are higher than those required for  voice calls, so you can have your broadband on and make phone calls at the same time. Additionally, the high frequencies mean that it can transmit more data, which makes for faster broadband speeds.

DSL encompasses several different types of connection – including ADSL (Asymmetric Digital Subscriber Line) where the speed to your home is faster than the speed from your home back to your local exchange, and SDSL (Symmetric Digital Subscriber Line)  a robust data-only line that has the same speeds upstream as downstream.

The main limitation of DSL is that the distance between your computer and the exchange can seriously affect your broadband speeds. The further you are from the exchange (using the route your phone line takes, NOT as the crow flies) the slower your broadband speed will be, to the point where some people cannot receive DSL broadband at all.

By Sarah at UK Broadband Finder
Read my Broadband Glossary disclaimer

Dynamic IP address

June 16, 2007

A Dynamic IP address is one that changes each time you go online. All computers need an IP address when they connect to the internet, so they can be identified by other computers. Websites need fixed IP addresses. However casual web browsers don’t – so they are often allocated a dynamic IP address by their internet service provider (ISP) which changes each time they go online.

An IP address is made up of four sets of numbers with each set separated by a dot. Each set of numbers is between 0 and 255. With the extraordinary growth in the numbers of people going online around the world, it is easy to see that IP addresses based on number combinations could run out.

So if an internet service provider gives a web user a dynamic IP address, it reduces the need for IP addresses in general as the IP adresses a provider owns can be re-used. The internet service provider also saves money as it only needs enough IP addresses for the number of people likely to be going online at one time, rather than having to ensure that each subscriber has a specific IP address available to them at all times (which is what it would have to do if they gave each subscriber a fixed IP address when they signed up).

By Sarah at UK Broadband Finder
Read my Broadband Glossary disclaimer

DSLAM

June 14, 2007

DSLAM stands for Digital Subscriber Line Multiplexor.  DSLAMs are sophisticated modems that telecoms companies install in their exchanges to connect many broadband subscribers to one high speed line, known as a backbone.  The DSLAM means that fast ADSL broadband can be achieved over a DSL line; manages voice and data traffic from the DSL lines; and forwards data from the subscriber to the ISP or network.

Several subscribers’ DSLs (Digital Subscriber Lines) are linked to one DSLAM. The more DSLAMs a company has, the more subscribers it can manage.

By Sarah at UK Broadband Finder
Read my Broadband Glossary disclaimer

On Demand TV and Video

June 11, 2007

Broadband providers are increasingly offering on demand TV and video services via a customer’s broadband connection. These may be free, or pay-for.  Services include:

  • BT Vision from BT – will provide digital TV over broadband to BT Total Broadband users.
  • 4OD, from Channel 4 – video on demand (of Channel 4 programmes) delivered via yourcomputer.
  • The BBC’s iPlayer – when it launches, it should include BBC Television programmes available for download, free for UK licence fee payers, for up to a week after transmission.

On Demand TV is bandwidth-heavy so users will need a robust and fast download connection in order to make the most of it.

Not all IPTV services are on demand – IP TV refers simply to the method of delivery and could include scheduled programmes, while on demand TV is available when the customer wants to view it.

By Sarah at UK Broadband Finder
Read my Broadband Glossary disclaimer