All ADSL is not equal (What is ADSL?)

Member Name: Asylum

Product:	What is ADSL?
Date:	29/09/02 (256 review reads)
Rating:

Advantages: fast, 24 hours per day

Disadvantages: slightly expensive to set up

ADSL stands for Asymetric Digital Subscriber Line, which simply means that the download and upload speed are not the same. The usual figures would be 512 kps download and 256 kps upload, a fair balance considering that most people would download data or web pages more often than they would upload to the internet.
In order to qualify for ADSL connection your telephone line must be capable of supporting the feature, although the majority of areas are now covered by this. You will also require an ADSL modem which usually plugs into the USB port on your computer. Expect to pay around £60 for a modem and around £65 for your telephone line to be configured for the service.
The obvious advantages over a standard internet connection via a 56 kps modem are the superior access speeds and the fact that your system is connected 24 hours per day. There is also the benefit of having your telephone line available while online. ADSL uses a higher frequency than your telephone, so both can be transmitted along the line without any conflict. A device known as a Splitter is used to separate the two frequencies at your telephone socket, so both can be used at the same time.
With many ISPs now offering the service for under £25 per month it is within the reach of the average surfer and is naturally increasing in popularity. However, there are more factors to consider before choosing an ISP than the monthly cost alone.

Here are a few points worth considering:

Static or Dynamic IP address.
The IP address allocated to your computer operates in the same way as a telephone number and allows other computers to link to it. This is important when downloading files or even accessing e-mail etcetera.
A dynamic IP address is allocated automatically by the ISP whenever you link to their server, the actual address being different each time you connect. In the case of a static IP address, this is a permanent and unchanging address as suggested by the name.

To most people the difference is not important, but if you wish to connect remotely to your computer from elsewhere, (such as accessing your files while at work or vice versa) then a static IP address would be required.

NAT or no NAT
NAT stands for Network Address Translation and is the protocol used when setting up a network. If you are simply using the service on a single computer then this will not matter to you. However, if you have more than one computer and wish to create a home network in order to access the internet from any source then a NAT enabled service is required. Some ISPs will even cancel your account if you try to create a network from a non NAT supply on the grounds that you have broken the terms of your agreement.

Contention Rate
The contention rate is the number of other users with whom you share a supply. The standard figure is 50:1, which means that 49 other people share the bandwidth allocated. The smaller the contention rate and the less loss of speed will be experienced when everyone uses the internet at the same time.
Unfortunately there are very few options available to avoid this. The ratio of 50:1 is standard and in most cases the only other option is to use a business account offering around 20:1 ratio, which is not practical due to the serious increase in cost. Hopefully other options will be offered in the near future to give people a realistic choice.

If you use the internet on a very regular basis, then upgrading to ADSL is very well worthwhile. However, take care to choose the right ISP and service before signing up. Most services have a minimum contract of 12 months, so if you decide that you have made a mistake you may still have around £300 to pay whether you use the service or not.

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