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PC Doctor+ Guide 8 Broadband Overview |
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Broadband: An Overview
In the old days, life was simple. Your only real decision
before accessing the Internet was whether your dial-up connection used the
U.S. Robotics V.90. standard or the Rockwell K56Flex standard. Some ISPs
supported both - some didn't. And that was it.
Of course, if you were independently wealthy you might
consider an ISDN line or even a satellite connection but both were expensive
and not really serious options for non-business users.
Fortunately, things have changed. You can now get a broadband Internet
connection for less than you spend each month on your weekday morning break
and that's not counting the bacon sandwich. But their remains a BIG DECISION
to make: DSL or Cable?
To help with that choice, here's a quick review of the two
technologies.
DSL (Digital Subscriber
Line) is actually a group of
technologies any one of which can provide high-speed Internet access over a
standard telephone line - as long as you are close enough to the nearest
telephone exchange where BT keeps its switching equipment.
DSL provides a direct dedicated (i.e. not shared)
connection between your DSL modem and an ADSLAM (Asymmetric
Digital Subscriber
Line Access
Multiplexer) at the telephone exchange.
The most common form of DSL is ADSL or Asymmetric
Digital Subscriber
Line. It's called asymmetric because it
delivers a higher download transmission (from the Internet to your computer)
than it does upload (from your computer to the Internet). Most of your
Internet work will consist of downloading data - the data that is translated
into an image on to your screen by your browser. Uploading only occurs when
you send e-mails or send files to store on a web server such as when
uploading a website.
In the UK, the BT network is currently used by all ADSL
providers including BT Yahoo of course. Other ADSL companies such as
Freeserve, Virgin and Tiscali lease capacity on the BT network re-selling it
to users as part of their own ADSL packages.
Cable Internet access uses the very same Cable that brings Cable TV into
your home (whether you actually subscribe to Cable TV or not) by keeping
some of the Cable total bandwidth reserved for Internet use. The Cable
company has their own equivalent of a telephone exchange but the Cable
between it and your house is shared not only between TV and Internet use but
importantly, it is also shared between yourself any of your neighbours that
subscribe to the same service.
Incidentally, Cable Internet is also usually asymmetric,
with more channels given to downstream traffic than upstream. Most of the
time that's the best solution because normally you will be downloading
entire web pages and all their graphics while uploading only an occasional
file.
With Cable, distance is not the issue so much as whether the Cable has yet
been routed to your street or area. Sharing though can be a big issue,
because the transmission can get slower and slower as more people in your
neighbourhood try to download all of those web pages and their graphics.
Now, to decide which of these options is the best for you here are some
things to consider:
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Availability |
You may live too far from the telephone exchange to use
ADSL or Cable may not have come to your area yet. If you only have access
to one or the other of the two options then the choice is made for you.
BT are prioritising the conversion of exchanges to ADSL
capability with the more populace urban areas being converted first.
People in more rural areas can register their interest in connecting to
ADSL and if enough people show an interest to justify the conversion cost
BT eventually go ahead and convert the nearest exchange - the threshold
seems to be about the 500 mark which is not particularly high. Bt are
often criticised for this policy but one has to bear in mind that the
Cable companies have virtually abandoned the rural areas to satellite TV
because of the costs involved compared to the potential returns.
Many residential areas have both ADSL and Cable
available. Generally ADSL is the more widely available of the two in
business areas. Cable was, initially at least, primarily targeted at
residential areas because the return per £ invested was both easy and
quicker to obtain .
Well thanks to OFTEL (and no thanks to BT) ADSL packages
have started to vary widely as competition takes root. You need to
consider four things here:
- The Monthly Charge
- The Cost of the Modem
- The cost of installation
- The plethora of 'special offers' currently available
Often the modem and installation costs are waived but
(understandably) require a minimum contract period.
Cable companies also include an optional TV service
which can make the the available 'packages' a bit more difficult to
compare with straight ADSL packages.
Your ADSL and Cable providers can both give you numbers
for upstream and downstream transmission rates - but take them with a
pinch of salt. All such figures are maximum rates and no matter which
connection option you choose it is subject to the conditions prevailing at
any moment on the Internet on the other side of the telephone exchange or
Cable Network. Both ADSL and Cable use the same shared links to the
Internet - so that part at least is a level playing field.
Uniquely, Cable can be further affected by the amount of
local traffic. Ask around your neighbours to see what kind of experiences
they have had with their Cable connections. More often than not it's no
problem at all and few people seem to be affected. However, you may be
unlucky enough to live in a high use area - high enough to affect speed
(remember that shared connection?).
At any rate, you need to be happy before you lay down
your money.
Such is the competition now between UK ISP Broadband
suppliers that's it's hard to keep up with the latest deals. On our
comparison page you'll find details of prices and other factors that
should help you decide what's best for you. We update these regularly.
However, you should regard these prices as the standard prices charged by
each ISP. They may not reflect ' this months offer '.
We've tried to get around this by including banners from
the main ISPs which pull in the latest offers automatically from their own
websites. Taking a regular look at the banners should keep you bang up-to-
date with the what's on offer.
One last thing to consider is the reputation of the
companies. In practice ADSL and Cable have more similarities than
differences and the quality of your service could very well depend more on
the service provider than on the technology you choose. Ask yourself a few
questions such as:
- How much is their support line?
- What is their customer service like?
A frequent comment of both ADSL and Cable users is that
the speed and service is great - until something goes wrong! Then you can
find yourself in long, call-centre queues at 50p or even £1 a minute
listening to Bach, Beethoven or even Steps. Talk about stress!
A Few ADSL and Cable
Myths
1) Because it is Shared Cable
is not Secure.
A common misconception is that because all of the Cable subscribers in a
neighbourhood are actually on the same Cable and do form a computer network
of sorts it is possible for your neighbours to browse your own computer just
as if you were all on the same Local
Area Network.
The truth is, not only do many Cable companies encrypt
your traffic with unique subscriber keys but upstream and downstream traffic
is carried on different channels and Cable modems cannot monitor the
upstream channels. Your neighbours have no more access to your computer than
any determined hacker on the Internet would (but that's another story!).
2) Running a Server on your
Cable Connection Won't Affect Other Subscribers.
This is technically true but what matters here is that servers typically
create much more upstream traffic than normal web browsing. There is a
limitation in the TCP/IP protocol itself that causes downstream traffic to
slow down as much as 80% when the upstream channel gets saturated. This
Internet phenomenon is called 'upstream saturation'.
A few servers in your neighbourhood may not matter but too
many will create a crunch for everybody and for this reason some Cable
companies prohibit servers on their connections. Home users aren't likely to
be running their own servers so the real question is how many businesses are
in your neighbourhood and how many of those are using a Cable connection.
3) You Can Only Get Cable
Internet if you Subscribe to Cable TV.
No it's not true. There is an argument to say that the TV signal is already
on the Cable and it takes an extra step by the Cable engineers to block it
out so maybe there's a case for an extra charge for this 'service' but in
practice the Cable companies grin and bear it. The Cable company will say
that the cost of its 'combined' packages is cheaper than paying for a
broadband and satellite TV separately which it probably is. In fact, the
case for combining Cable Internet with Satellite TV is pretty poor compared
to the full Cable alternative. However, if all you want is the basic TV then
stick to the terrestrial channels that come through your aerial for now or
treat yourself to the BBC's FREEVIEW box for a one-off payment and settle
for the 30 digital channels it offers.
4) ADSL is both Easy to Get and
Easy to Install.
These are both IFFY.
- IF you live within 17,000 feet (about 3 miles) of a
telephone exchange (by the length of the wire - not 'as the crow flies')
- IF BT already offers ADSL in your area
- IF they aren't backlogged on installation
- IF there is a clean, quiet phone line with no crosstalk
already coming into your home
then getting ADSL is easy.
That means at least 25% of us are just flat out of luck
(LOL).
As for installation, self-installation is cheaper and
therefore more popular but potential problems abound. For example, noise on
the electrical lines can get transferred to the phone line through the ADSL
modem so if you have poor house wiring, dimmer switches on your lights etc.
be prepared for some headaches getting your ADSL to run without errors.
5) ADSL Can Share Your Home Phone
Line and Won't Interfere.
True. You can usually run ADSL on the same line you use for regular
telephone service and even do voice and data at the same time but you must
put a special filter on each extension where you have a phone plugged in.
You will usually get at least 2 such filters with your ADSL pack.
6) The ADSL Upload Capacity
Has No Affect On the Download.
Most residential ADSL services have a maximum upstream capacity of 256Kbps
based on a quoted 512kbps connection which at present is the most common.
ADSL is affected by upstream saturation just
like Cable. This is a limitation of the TCP/IP protocol used by the Internet
and not of the type of Internet access you use.
This means that if your upload traffic approaches the
limit, for example, if you are uploading a large web site, your downstream
speed may also drop quite noticeably. Unlike Cable, however, at least you
only have to worry about your own traffic and are not what your neighbours
are doing on their connections. If you mostly just browse the web and send
text e-mails you won't need to concern yourself with upstream speeds.
That said, if say, you have your own web site and you
frequently perform large uploads it might be worth finding out if your ADSL
provider has any upgrades on offer with higher upstream capacity - and yes -
it will cost you more !
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