A digital subscriber line (DSL) is an inexpensive digital solution that transports high-speed data from your phone company's central office to your company's network. The data is transmitted over the same copper wires used by most phone systems.

DSL internet service is very distance-sensitive. The closer your company is to the phone company's central office - where phone lines connect to switching equipment - the faster your connection. It is generally recommended that your office be located within 2-3 miles of the central office for faster, more affordable service. Beyond 3 miles, you would only qualify for low-speed DSL internet service - if any at all.

You can find out if you are within range for DSL by calling your local ISP, or looking up your location online. There are many Internet sites that allow you to check if your area can get DSL internet service and how fast a connection you qualify for.

Types of DSL Internet Service There are various types of DSL (referred to as xDSL). The two most common are Symmetrical DSL (SDSL) and Asymmetrical DSL (ADSL).

ADSL uses your existing copper phone lines to transmit data, but limits upload speeds to as little as one quarter of download speeds. SDSL is a more robust (and more costly) version of DSL that supports equivalent upload and download speeds. This is good for companies that regularly upload large files, but requires dedicated wiring.

The downsides of business DSL Reliability is the primary concern with DSL. On average, the uptime for DSL isn't as good as it is with a T1 connection. Service level agreements (SLAs) that ensure your connection will always be running are often not offered with DSL service. And while a DSL connection can support many simultaneous users for sending e-mail and surfing the web, it's not optimal for applications requiring a lot of bandwidth such as large file downloads or streaming video.

DSL internet service also runs into the problem of slow connections due to oversubscription - the act of selling more bandwidth than is actually available. DSL providers will sign up more subscribers than they have bandwidth for, with the expectation that not all users will be online at the same time. While you'll get faster connection rates - up to 2 Mbps - when there aren't a lot users online, your connection will lag when more customers connect. This can be highly frustrating, to say the least.

In the end, the savings you may gain from using DSL can be offset by how much you compromise critical business applications like internally maintained e-mail server or web servers.

Necessary equipment
Most business DSL customers use a router to connect their local area network (LAN) to the Internet. While more expensive than a standard DSL modem, a router provides data security and data filtering services, which are valuable in business environments. If you have fewer than 10 computers to connect, you can opt for a less expensive DSL modem, although you will still need to purchase firewall software to secure your network. Your DSL provider will lease or sell you the appropriate hardware.