An Introduction to DSL

Digital Subscriber Line ( DSL) offers high-speed, always on Internet access. However, the sign-up process is no bed of roses. Knowing the pitfalls can help you make more informed choices and can make the process smoother. With that in mind, here are a few of the things you need to know before you make the I-want-speed-baby phone call.

The Parts

The first, and most important part, is the company you deal with: the Internet Service Provider ( ISP). They are the people who provide you with DSL access to the Internet. In the course of doing this, they may need to contact the phone company to make sure you have all the appropriate wiring in your home or office.

DSL requires more than just a phone line running from your computer to the wall. The computers in your office are connected via a network. One of those computers will be connected to the Internet via a DSL modem. Your modem will be given (in the same way a cable box is "given") to you by your provider. However, this only connects one computer. For any of your other computers to take advantage of the service, you will need a router -- a device that allows you to distribute the connection to various computers. This router may be a separate piece of hardware, it may be a part of your DSL modem, or it may be provided by software installed on your computers. Be sure to ask your ISP which solution works best with their service.

DSL is Not a Right

You may have the parts. You may even have the local provider. You still may not be able to get DSL. Service is made available to you by the phone company (who, by the way, may or may not be the provider you choose), and it is not available to everyone.

One of the main considerations is your distance from the phone company Central Office ( CO). For DSL to work at high-bandwidth speeds, you need to be within 18,000 feet of your CO. The further you get the slower your service. Often, the phone company will not provide you with service because the quality -- the speed of your connection -- will be poor. Some other companies, however, may provide you with lower bandwidth connections. These connections may still be faster than what is provided by your standard modem.

You will also need to be sure that your office computers meet the minimum system requirements given by the ISP you choose.

Finally, those $39.95/month prices you hear on the ubiquitous radio commercials may not apply to you. Many of those service plans are available only to home (read: not office) subscribers. Pricing varies greatly depending upon your needs and available ISPs. You won't know exactly what you are going to pay until you are the phone signing up for the service.

Don't Dial That Phone Yet

You need to know the number of IP addresses you'll need. Like street addresses, an IP address identifies your computer so that information can be sent and received over the Internet.

Inexpensive DSL accounts provide you with only a dynamic IP address. Each time you log on, your computer is assigned one of a pool of addresses made available to you by your provider.

This can be a problem for a networked office. For example, if you are running an email or web server, you will need one IP address that is dedicated solely to that server. You will need a second IP address to connect your networked office computers. The router will take care of splitting that IP address out to the various computers. Be sure to let your ISP know you are connecting a network. This can affect pricing and availability.

To be sure that all of your computers can take advantage of DSL service, have the specifics of your computers (operating system, processor type and speed, amount of memory) on hand to be sure they meet the minimum requirements established by the provider.

Once You've Ordered

Now, you get to wait. DSL requires a trip to your office by installers. The current high demand for services means it may be a week or more before you are able to schedule an appointment.

And it's possible, that once the installers arrive, they'll discover faulty wiring, incorrect service assessments or some previously unforeseen DSL gremlin which prevents you from getting service. These problems can sometimes be fixed by a second trip or with the help of your phone company. They may, however, require more extensive and/or costly solutions. Or, it may be that you simply cannot get DSL.

An Open Book

Unfortunately, that much-touted, always-on Internet makes your computer vulnerable to people outside of your organization. Firewalls -- programs or hardware that shield your system -- are available to protect your files and data. You can find the answers to your burning firewall questions at: About.com Network/Internet Security or Internet Firewalls: Frequently Asked Questions by Matt Curtin and Marcus J. Ranum. You can also visit networking guide, Russ King's special report, "Firewalls and You" in the Computer Networks section.