FAQ for DSL Internet

DSL stands for digital subscriber line. It is a technology for transmitting high-speed Internet service over existing telephone wires in many American homes.

DSL service essentially divides a typical phone line into three distinct channels. One high-frequency channel is maintained for analog voice service. The other two channels allow high-speed data transfer between a computer and the Internet. A filter adaptor keeps the analog telephone signal separate from the data signals.

Several acronyms describe variations of DSL service, of which two are the primary methods. ADSL stands for asymmetric DSL and is the typical type of DSL service provided to consumers. ADSL provides higher download speeds than upload speeds. Its alternative is SDSL, or symmetric DSL. Business clients who need to upload data as well as download data at high speeds typically use this type of service. Other variations of DSL service include DSL Lite, which is a slightly slower but cheaper version of ADSL; HDSL, or high bit-rate DSL, a high-speed variation of DSL reserved mostly for corporate customers; IDSL, or ISDN DSL, which is a hybrid of DSL and dial-up technologies; RADSL, or Rate Adaptive DSL, which can dynamically vary data transfer speeds; and NDSL, or Naked DSL, which allows DSL service without the analog voice channel.

The main benefit of DSL service is that it provides high-speed access to the Internet. Actual speeds vary based on a number of criteria, but DSL service can range from 128 Kbps to 6 Mbps. The reason that DSL has become one of the de-facto technologies for providing broadband data service is that it uses existing infrastructure, namely the copper telephone wires that already run into most American homes. In addition, DSL allows subscribers to continue to use analog telephone service without requiring the purchase of a secondary phone line.

DSL's reliance on existing copper telephone wires has a limiting effect compared to other, newer high-speed networking technologies. Most DSL service tops out at about 6 Mbps. Cable and fiber-optic networks can provide much higher speeds due to the use of higher bandwidth infrastructure. Additionally, DSL technology has certain geographical limitations. DSL subscribers must be within a certain distance of the service provider's Digital Subscriber Line Access Multiplexer otherwise data rates will slow or be lost.

Aside from an Internet service provider capable of delivering DSL service to your location, DSL subscribers need a DSL-capable modem. Some computers have such modems built into them, while most ISPs will provide a DSL modem to subscribers. In addition, DSL subscribers who intend to use voice service on the same line will need a DSL filter for each telephone they will use. Finally, DSL subscribers who plan to set up a wireless hub or access the Internet from multiple computers will need a DSL router to manage multiple data streams.