Which DSL is which? A guide to broadband terms.
You would figure that DSL would stand for something futuristic and exotic like Digital Superelectroncharged Leapquantotronic but instead it is just the acronym for the rather pedestrian Digital Subscriber Line phrase. Boring!
As everyone who has not lived in a jungle island since World War II is aware of, DSL is a phone line based broadband connection which functions by splitting your existing landline telephone line into two or even three frequency bands. One of those bands carries the old fashioned voice telephone signal, while the rest carry the high speed internet signal.
The DSL signal flows into the standard phone line through a device called a DSLAM or DSL Access Multiplier. When it enters your premises, the phone line feeds to your conventional POTS (Plain Old Telephone Service) phones through a multifilter to keep the voice phone systems from interfering with the high speed broadband signals, and to your DSL modem which pulls out the broadband internet signal and feeds it to your PC.
There are many different types of DSL and their naming convention is confusing to say the least. Here's how to make some sense out of which DSL is which.
ADSL: This is the generic name for Asymmetric DSL which is generally applied to professional-strength or business-targeted broadband connections with download speeds that can exceed 20 Mbps. Although prices for this service have been coming down steadily, you should still expect to pay around $40 to $50 a month for it. Watch for user limits! Some ISPs are now imposing limits to squelch torrent downloading and you could pay $20 per additional GB or even more if you exceed your monthly allocation.
ADSL Lite: This version comes under various monikers and is generally offered around $25 a month. It is the same as normal ADSL except that it is generally limited to about 1.5 Mbps download and 0.5 Mbps upload. Even though the upload speed is not usually an issue, the download speed can be, especially at times of peak usage like early evenings when everybody and their brother is online. It's generally not worth it, and you're much better off to spend an extra 50 cents per day or so and get full ADSL.
HDSL: High Bit Rate DSL. You might think that this is some sort of super ADSL, but instead it's just another name for ADSL Lite.
RADSL: Rate Adaptive DSL is supposed to vary your connection speed dynamically according to line conditions. Big Deal. They all do that. And usually to a slower speed.
SDSL: Symmetric DSL, also confusingly known as HDSL2 provides an equal, or symmetrical, upload and download speed. These connections are generally unobtainium as most ISPs shun giving torrent uploaders any more bandwidth than they absolutely have to.
VDSL: Very High Bit Rate DSL. This is the really good stuff. If you have fiber optic infrastructure in your area, it's well worth scrimping on groceries and biking to work to save on gas in order to be absolutely amazed as you download an entire one hour television program in about a minute. If you're a heavy duty user, you will pay the heavy duty price and be absolutely deliriously happy.
XDSL: It means nothing. It's just a generic label for all DSL.