Cable or DSL?

Analog modems have just about outlived their usefulness. They have definitely hit a speed roadblock. Their great advantage is universality - you can find a telephone jack just about anywhere.

ISDN was the first great challenge, using one or two digital phone lines to allow up to 128 kbps bandwidth. Since the best 56k modems tend to connect at around 44-48 kbps, ISDN is roughly 2.5 times faster.

But it's preposterously expensive in comparison to analog. The hardware costs more, the phone lines cost more, and most ISPs charge a premium for an ISDN connection.

High Speed Options

There are two promising alternatives to analog modems and ISDN: cable modems and digital subscriber lines (DSL).

Compared with 48k and 128k connections, both offer significantly faster connections. Cable modems may reach 30 Mbps download speeds; DSL varies by implementation (there are several different standards), but usually starts at 256k and can sometimes hit 6M.

Best of all, both cable and DSL should be more affordable than ISDN, which means ISDN may outlive its market in the coming years.

Cable Modems

Most cable TV systems use similar cabling to the coaxial ethernet cabling that used to be common in business environments. Potential bandwidth reached 30 Mbps, about three times the speed of regular 10 Mbps ethernet.

Also, most cable systems are hooking up with high speed internet backbones. Because the internet has a lot of connections far slower than even ethernet, this is the only way they can help you take some advantage of their high speed connection.

However, there are some drawbacks. Not all cable systems are bidirectional - some require you to use a regular analog modem to send commands and upload files, so you only get the high speed for downloads. If you're hoping to host a site on your computer or run a mail server, one-way cable modems are not for you.

Even on bidirectional systems, your cable provider may throttle back upload speeds, setting perhaps a 128 kbps ceiling on data you send to the internet. They do this to discourage you from running a web or mail server from your home - or to encourage you to sign up for a more expensive program with a higher bandwidth ceiling.

Another drawback is that many cable operators specifically prohibit connecting more than one computer the the cable modem. There are ways to share a connection that may make it difficult or impossible for them to detect multiple computers connected to their system, but they really want to sell you a more expensive package if you wish to connect more than one computer to their system.

Finally, cable is a shared medium. If you're the only one in your neighborhood using a cable modem, you'll have simply amazing throughput. But if a dozen neighbors are also using cable modems, each of you will have slower overall throughput because all the data from each user has to share the same wire.

DSL

Digital subscriber lines are not as fast as cable modems. More accurately, they don't provide as much bandwidth.

However, DSL is a point-to-point connection using regular phone lines. This means you're not sharing your internet connection with your neighbors. You'll probably still have less throughput than cable, but not necessarily by much.

In fact, a recent study in San Francisco showed DSL and cable modems offered comparable download speeds. At certain times of day, cable was slower due to the number of users, but at other times it edged out DSL. But in that test overall average speed was virtually identical.

DSL may be available in several configuration, most of which offer separate upload and download speeds. You may sign up for a 1.5 Mbps download, 256 kbps upload package, or one that offers 384 kbps in both directions, or one of several other options offered by your internet service provider (ISP).

Again, you'll probably find most DSL suppliers only allow you to connect on computer to their network - unless you want to pay more.

The biggest advantage of DSL over cable is that phone lines are just about everywhere, while not everyone has cable TV.

Which is better?

In the real world, cable modems and DSL are available in limited markets. A few areas have both options, more areas have one or the other, and a whole lot of us have access to neither.

Either is a huge step up from analog or ISDN. If either were available to me, I'd switch as fast as I could get an installer to set up the hardware.

But if both were available in my area (alas, neither is), my choice would be DSL.

With DSL, I would have guaranteed bandwidth; cable modems can't promise that, since you have to share bandwidth with an unknown number of other users.

DSL works with existing phone lines, so I wouldn't need to have the phone company install a second line. In fact, this is a big advantage over ISDN and analog modems - you can use the phone to talk or fax while you DSL connection is active.