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RSS feedsImagine an always-on connection to the internet that's 10 times faster than your 56K modem, and costs as little as £40 per month. This is the dream of the much talked about asymmetric digital subscriber line (ADSL) service, but it's not all good news.
BT's OpenWorld implementation of ADSL comes with a number of important limitations and, while the OpenWorld website FAQ mentions some of them, none are explained in any detail. If you're thinking of taking up ADSL, you should be aware of exactly what you're getting.
Local exchanges
The most important limitation of OpenWorld affects whether you can use the service at all. If you want to use it, you have to be within 3.5km of your local BT exchange, which itself has to have been modified. BT reckons it has already upgraded exchanges covering 35 per cent of UK households, but that still leaves 65 per cent out in the cold.
Fast connections
Even if you can be connected, don't expect your £40 per month (the cheapest ADSL service) to guarantee you a 512Kbits/s download speed. OpenWorld is a shared service that has anything between 20 and 50 users on a single ADSL connection at the exchange. This is technically called the 'contention'. A 512Kbits/s connection may sound like a lot but with 50 people using it, it'll soon slow to a more recognisable modem-like rate.
Providers believe this won't be an issue, claiming that most users won't be constantly using ADSL for the things it actually makes possible - downloading large files and streaming audio and video. Instead, they reckon that most people only use the internet a few seconds at a time - to bring up a new web page or send an email. At this early stage, the impact of sharing is yet to be seen.
A final point concerning fast internet connections is that, even if you do have an entire ADSL connection to yourself, your web experience may still not be 10 times faster than you get from using a modem.
The internet is only as fast as its slowest connection, and this won't always be the one between it and your PC. Large corporate websites, such as those of the BBC or Microsoft, will download very quickly with ADSL, but others won't. Some sites are simply slow to respond to a browser request, whether you're using a 56K modem or a fast office network.
Security
Few people realise that when your PC is connected to the internet, the internet is also connected to your PC. With typically short dial-up connections this isn't much of a problem, but with ADSL you're permanently connected, leaving your PC open to attack from malicious web users.
There are two solutions. The first is to ask your provider for an option called Network Address Translation (NAT). This lets you hide behind your ADSL box, protecting yourself from almost anything. The downside is that it blocks many of the things you wanted to use the web for in the first place. Microsoft NetMeeting won't work with NAT, for example, and nor will the ICQ chat client.
However, NAT is only an option on the more expensive business ADSL services so, in theory, users of the cheapest £40 per month package won't have anything blocked (although BT may selectively limit certain services for other reasons). If you don't use NAT, then you'll still need some kind of protection, and that means getting hold of the second solution - a firewall.
Firewalls
In the past, firewalls were expensive boxes configured by network experts to protect entire companies, but new breeds are arriving all the time. For home and small office users, these take the form of software and there are several products available.
If you want to pay for one, the Norton Personal Firewall 2000 from Symantec is a good bet at around £30. If you don't, then ZoneAlarm is a free download to non-business users. It sits in your system tray and is configured to let internet traffic flow freely, or be restricted to and from various applications. It is highly recommended.
Read the small print
If you move house, you'll have to pay for the remaining term of your 12-month ADSL contract on top of starting a second at your new location. In addition, while ADSL works over a normal line and lets you use your phone at the same time for analog calls, BT admits that faxes and analog modems may operate at lower speeds. You should also remember that, since ADSL is dependent on your analog phone line, if this fails, it'll take your ADSL service with it.
And BT - which until next summer provides all ADSL networking to end users - does not offer a guaranteed level of service for ADSL and, indeed, our trial service was unavailable for a few minutes on several occasions during the space of a week.
And finally ...
The big problem with ADSL at the time of writing is that the only service available for testing was the business ethernet package that uses NAT. Consequently, no-one has any real idea how the cheapest consumer package that uses USB will fare in terms of installation, service compatibility and performance.
What we can say is that Demon's trial NAT service is extremely fast and works very well with email, web browsing, audio and video streaming and AOL Instant Messenger (but with variable direct connect success).
But even with all the above caveats, heavy users of the internet will adore ADSL.
See also:
If you're just about to sign up for an 'always-on' connection, you should be considering installing software that will keep undesirable elements of the internet out of your computer. 20 Dec 2000All Online
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