The Scoop

Limitations aside, many telephone companies have great expectations for digital subscriber line (DSL) technology. But in competition with cable modems, to which it is most often compared, DSL is lagging behind.

At the moment, cable modem access to the Internet is outstripping DSL by a ratio of about 10 to 1, but the game is still young.

So little of either service has been sold that they barely register as blips on the Internet-access radar screen. Generous estimates put the U.S cable modem and DSL customer total at about 650,000 combined.

Gecko Research tallied 600,000 cable modems in use in the U.S. vs. 15 million households that could have bought the service - a penetration of 4%.

DSL runs over regular phone lines, and with 177 million phone lines in the U.S., DSL penetration is so far below 1% that a statistician would say that for all intents and purposes DSL services do not even exist.

Nevertheless, both technologies hold promise as high-speed on-ramps to corporate networks and the Internet. Each technology has its strengths and weaknesses.

The main problem with both services is that they are not universally available. A corporate customer trying to piece together a broadband remote access strategy might have trouble getting either service for all sites.

Cable is plagued by the problem that bandwidth is shared by all cable modem customers on a given network segment. That means bandwidth available to any one customer can vary widely depending on how many other customers on that segment are using the service and for what purposes.

As the DSL story (this page) points out, DSL has potential bandwidth problems of its own - you may not be getting the bandwidth you think you are due. Furthermore, the lack of quality lines means DSL may not be available to 30% of customers in certain areas.

To overcome line problems, some carriers may offer lower-speed DSL service, sometimes as low as 128K bit/sec. The upside: Even at that speed, DSL will be perceptibly faster than dial-up modems.

Much of the future success of DSL and cable modems depends on the variety of services they will come to support.

For example, cable and DSL vendors are working on augmenting data services with voice. Some forms of DSL already support one voice channel, but vendors are coming out with gear that can stuff up to 15 digital voice channels into a single DSL stream.

Cable providers are also investing heavily in upgrading their networks to support telephony, but they are at a disadvantage because they lack experience with telephone switching and billing.

Beyond technical aspects, cable and DSL are coming closer in price. Service providers in both camps now offer Internet access for as low as $40 to $60 per month for basic service.

- Tim Greene