In ADSL
(‘asymmetric digital subscriber line’ - the most common form of DSL), the total
available capacity of the high speed digital subscriber line is split
asymmetrically between downstream and
upstream directions of transmission –
there is a much higher bitrate made available for downstream transmission – at the expense of the upstream transmission rate. The
advantage of this is that information transferred downstream (e.g. delivery of webpages, software downloads etc. out
of the Internet to the user’s PC) can be delivered much more quickly. Since
little information is sent upstream
by the typical Internet surfer (e.g. only the odd ‘click’ message or short
email), the asymmetry of ADSL benefits the user.
ADSL is a
particular type of DSL: indeed ADSL is often referred to simply as ‘DSL’, since
ADSL is the commonest form of DSL. (Note:
All ADSL lines are ‘DSL’ lines – and many ADSL services are simply marketed as
‘DSL’. E.g. T-DSL, Deutsche Telekom’s german version of DSL is actually an ADSL
service. But remember that not all DSL is ADSL). ADSL is a technology used to
provide a digital highspeed internet access line over a ‘normal 2-wire
telephone line’. Over an established telephone or IDSN (digital telephone)
line, the public telephone company uses ADSL technology to provide the high
speed ADSL internet access line sharing the same 2-wire connection to
the public network.
The fact
that the ADSL line can share the same 2-wire connection as the user’s
(analogue) telephone or ISDN (integrated services digital network) telephone
line is important, since it affects the equipment which must be provided for
the ADSL service (DSL splitter/filter and DSL modem) and the economics (price
to the user).
More...
What is.... ADSL2+?
Your ADSL connection... What do I need for DSL / ADSL?
When is DSL / ADSL the best Internet
Access connection for me?
Reasons for buying ADSL
(applications of ADSL)
Choosing the right ADSL
connection type... ADSL connection types
Should I buy the highest
possible ADSL bitrate?
Deciding on ADSL
service... Choosing your ADSL service provider
Must I buy a
telephone line from my ADSL service provider?
Choosing an configuring your DSL modem
Will my telephone line length affect the ADSL
service I get?
What are the alternatives if you can’t get ADSL?
Setting up &
operating your ADSL connection... ADSL Network configuration
What to do if the download speed appears slow
Internet or Broadband
Telephony... Introduction to VOIP (voice-over-IP)