The ABCs of DSL
by Jim Capobianco

At times my Internet connection is painfully slow. My computer is a Pentium III at 600 MHz with a 56K modem. Off line I compute at lightning speed. But on the Internet, I feel like I'm in s-l-o-w m-o-t-i-o-n.

Enter DSL.

DSL, which stands for Digital Subscriber Line, is a high speed connection to the Internet.

It uses standard copper phone lines, but differs significantly from the traditional dial-up Internet service many of us use in our homes.

Imagine your copper phone line is a two lane highway. DSL uses one lane for your Internet connection and the other lane for your fax or voice conversations. The neat thing is you can do both at the same time. That is, talk on the phone and surf the net simultaneously.

Scientifically speaking, DSL enables data to travel down the "highway" at a higher frequency than voice traffic.

The second major difference between DSL and dial-up Internet access is with DSL your Internet connection is "always on". Your modem does not have to dial into the Internet, once your computer is on, your connection to the Internet is on too.

Then there is the speed.

DSL providers typically offer a range of speeds, all of which are faster than a standard 56K modem. Downloading a file from the Internet might take 15 to 30 minutes using a 56K modem. The same file would take 24 to 48 seconds using DSL.

DSL comes in various "flavors", with higher costs for higher speeds. The two most common being ADSL (Asymmetric DSL), in which download speeds are faster than upload speeds, and SDSL (symmetric DSL), in which uploading and downloading are equally as fast. ADSL is best for small businesses. It's relatively cheap and if you are not transferring lots of large files regularly, you don't need fast upload speeds.

The final major consideration is availability. DSL can't be delivered to every home because it can't be pumped over long distances.

The rule of thumb is you must be within about three miles of the phone company's central office. Most DSL providers can figure this out for you. There are cases, however, where the rule doesn't always apply. Your home may be close enough to the phone company, but your telephone line takes too many twists and turns and puts DSL out of reach.

For information on DSL, there are several web sites, including http://www.dslreports.com and http://www.xdsl.com, which provide lists of DSL providers, customer reviews, and answers to frequently asked questions.

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