he ''D'' in ''DSL'' is supposed to stand for digital. The other two letters stand for the words ''subscriber line,'' which is telephone company jargon for the wires that run from the firm's central office to your home and business. Together, the letters DSL stand for a new technology that is bringing high-speed Internet access to many homes and businesses nationwide and, increasingly, throughout the world.
There are basically two ways to get DSL service in Boston. The first is through an established Internet service provider, such as Harvard Net or Shore Net. Call one of these ISPs, which are marketing mostly to businesses, and it will order you a second telephone line for the DSL connection.
Getting this second phone line can take anywhere from one to two months - and sometimes longer. The price of the connection depends on how fast you wish to connect to the Internet: Typical prices are $200/month for a connection that can send 384 kilobits per second, or $300/month for a connection that runs at 768 kbps.
The second way to get DSL service in Boston is directly from Bell Atlantic, using the new InfoSpeed service introduced earlier this year. Bell Atlantic is initially targeting residential subscribers, aggressively marketing DSL as a high-speed alternative to dial-up Internet access. The company says InfoSpeed is a secure alternative to cable modems, which it refers to as a ''party line.''
Bell Atlantic has a distinct advantage in offering DSL: It already has a telephone line in practically everybody's home. So when you order DSL from Bell Atlantic, you don't need to wait for a new wire to be installed. Instead, the company merely clips the DSL equipment on to your existing telephone line, which is then used for both voice and data.
Bell Atlantic has priced its DSL service at roughly $50 per month - about the same as my MediaOne cable modem, and a quarter the cost of a DSL connection from Concentric or Shore Net. To avoid cannibalizing its own data services, however, Bell Atlantic has put an interesting restriction on the connection.
Although download speeds can allegedly go as fast as 640 kbps, the upload rate is limited to 90 kbps. This restriction is designed to prevent people from running high-traffic Web servers or other Internet services on their home networks. By comparison, my MediaOne cable modem delivers 300 to 600 kbps in both directions.
I've gotten an incredible amount of e-mail from readers in recent months about Bell Atlantic's DSL offering, so I decided to try it. As things turned out, I was one of the first customers in Massachusetts allowed to ''self-install'' the DSL equipment.
Instead of having a Bell Atlantic technician come to my house and hook up the equipment, the company just mailed me a box. I plugged it in and turned it on. Within a few moments, a little green light appeared on the box indicating that the DSL line was operational. Unfortunately, it was also misconfigured: It took me two phone calls, and an hour waiting on hold, to get things working.
One of the first differences I noticed between the DSL and the cable modem was the speed. Although the DSL is supposed to run faster than the cable modem, in my side-by-side comparison tests I found that overall, the cable modem Internet connection was between 30 and 50 percent faster than the DSL.
For example, it took me 4 minutes and 54 seconds to download the 180-second trailer from the movie ''The Matrix'' over my cable modem; over the DSL connection, the same download (at exactly the same time of day) took 8 minutes and 3 seconds. The overall rate for the cable modem was 592 kbps, vs. 346 for Bell Atlantic's DSL. I had similar results downloading a copy of Netscape Navigator: 1 minute 27 seconds by cable modem; 4 minutes 27 seconds by DSL.
These download times aren't necessarily the fault of the DSL technology. Instead, they are likely caused by congestion at Bell Atlantic.NET, the phone company's own ISP. Unfortunately, while Bell Atlantic promises that other companies will ultimately be allowed to offer Internet service over its lines, right now there are no other choices.
Another significant difference between the cable modem and the DSL connection involves security. Since both connections provide ''always-on'' access to the Net, it's important that your computer be relatively secure so bad guys can't break into it. As I've written in the past, one of the easiest ways to break into a Windows 95 or NT computer over the Internet is to use Microsoft's file-sharing protocols: Many people inadvertently make their home computer's hard drive available for remote access without a password.
The good news for cable modem customers is that MediaOne automatically blocks Microsoft's file-sharing protocols on cable modems in the Boston area. MediaOne programs each of its cable modems to work like a mini ''firewall.'' Unfortunately, Bell Atlantic puts no similar blocks on its DSL service. Instead, it includes with the modem a brochure explaining the dangers of file sharing and advising customers to turn off file sharing before connecting to the Internet.
All in all, I'm rather disappointed by Bell Atlantic's DSL service. The company's one advantage is deployment: DSL is likely to be available in many communities not served by MediaOne or another cable modem provider. But given a choice between DSL and cable, I would choose the latter - at least until Bell Atlantic gets more experience in offering high-speed Internet service.
Technology writer Simson L. Garfinkel can be reached at plugged-in@simson.net.
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