CertiGuide to Network+  9  Chapter 0111: Wide Area Networking       9  V  High-Bandwidth Individual Remote Access

V  High-Bandwidth Individual Remote Access 1 2 3 Cable Internet

DSL (Digital Subscriber Line) is the telephone company’s answer for high-speed Internet access. Available at a wide variety of data rates (whose availability depend on your distance from the C/O, line quality, and how much you’re willing to pay to watch video and larger files from the Internet), DSL is a nice, reasonably affordable option for those who qualify for it.

And that dear reader is the DSL “gotcha”. Not everyone with a phone line can get DSL. Sometimes it seems like your residences (or small business’) eligibility for DSL depends, as much on the phase of the moon multiplied by the number of t-shirts you own, as anything. Reality is that a great many factors go into determining whether a particular location can subscribe to DSL.

Some of these include:

• Distance from phone company “central office” (or CO) switch/wiring plant
  
  
• Quality of wire between your site and the CO
  
  
• Make, model and age of the switch in the CO
  
  
• Simply, desire of the phone company to install the necessary equipment to support DSL at the CO

There are different types of DSL that provide different levels of throughput, and use slightly different underlying technologies. Why multiple types of DSL? Two primary reasons. First, the technology keeps advancing, and new versions of the technology tend to be incompatible with older ones, but are kept around because they’re still sufficient for many purposes.

Second, the slower/more expensive ones often work in areas that don’t qualify for the faster, less expensive varieties. Now let’s go over the features of the most significant varieties of DSL (as of 2002):

V  High-Bandwidth Individual Remote Access 1 2 3 Cable Internet