What is xDSL Technology?

The tech world is chock-full of acronyms. Unfortunately, it can be hard to get a grip on what all those letters mean, much less remember them. A case in point is xDSL technology and its many types (e.g., ADSL,  ADSL2, ADSL2+, ADSL Lite, VDSL, VDSL2, R-ADSL, and SHDSL). This article aims to discuss just what xDSL technology is and serve as a quick guide through this swarm of acronyms and jargon. 

So, let’s get started!

What is xDSL?

DSL stands for “digital subscriber line”; the “x” indicates many different DSL types. In other words, xDSL is a generic term for all kinds of DSLs. 

DSL delivers a high-bandwidth internet connection from a simple telephone wire (wall jack) that is directly connected to a modem. Telephone wires carry hundreds of thousands of frequencies while only using a few thousand for actual telephone communications. Therefore, DSL has plenty of frequencies available for file-sharing, transmitting pictures and graphics, multimedia data, audio and visual conferencing, and much more. DSL extender technology can provide additional network improvement.

DSL may no longer be cutting-edge internet connection technology (fiber is); however, it is far more likely to be available near a business or a home than fiber.  And while it may not be as fast as fiber, it provides speed levels that are entirely satisfactory for most households and small businesses. For business, this can be paired with cable management planning that provides room for future growth.

DSL internet service comes in two major categories: asymmetric or symmetric. Within each of these categories, there are different “flavors” of service. 

So, why so many flavors?

The short answer is that users have different needs. For example, the needs of a home user with one or two computers are not the same as those of a small business owner.

Before we discuss the DSL types individually, we want to note their key differences:

  • Speed: Also called “bit rate,” this is the amount of time it takes to send and receive data.
  • Line Coding: There are many different methods of decoding.
  • Number of lines: Are one twisted pair of wires required or two?
  • Distance Limit: Also called “reach,” this is how far the signal can travel and can still be reliable.

Asymmetrical DSL

According to TechTarget, this technology:

is asymmetrical in that it uses most of the channel to transmit downstream to the user and only a small part to receive information from the user.  ADSL was specifically designed to exploit the one-way nature of most multimedia communication in which large amounts of information flow toward the user and only a small amount of interactive control information is returned.

In other words, limiting the amount of bandwidth upstream (in the form of uploads) makes more bandwidth available downstream (in the form of downloads).

The most common types of asymmetrical DSL are as follows:

  • ADSL (asymmetric digital subscriber line) supports telephone service and data transmission simultaneously. It has a downstream rate of 8 Mbps (megabits per second) and an upstream rate of 384 Kbps (kilobits per second).
  • ADSL2 is the second iteration of ADSL and offers nearly twice the speed, as well as several improvements such as modulation efficiency, coding gain, and dynamic rate adaptation. It offers download speeds of up to 12 Mbps and upload speeds of up to 1 Mbps.
  • ADSL2+ is the third generation of ADSL and doubles the frequency band of ADSL from 1.1 MHz (megahertz) to 2.2 MHz. It delivers download speeds up to 24 Mbps and upload speeds up to 1.4 Mbps.
  • ADSL Lite (also called G.Lite) provides lower download speeds of up to 1 Mbps and up to 512 Kbps upstream speeds.
  • VDSL (very high bit-rate digital subscriber line) is the fastest DSL technology available, delivering downstream speeds of up to 75 Mbps and upstream speeds of up to 2.3 Mbps. However, this technology is particularly distance sensitive. According to telecommunications holding company, Otelco:

VDSL works for up to 4,500 feet from network equipment with a top sped of around 75 Mbps closest to the equipment that decreases to about 25 Mbps at the full 4,500 feet. Beyond 4,500 feet, the VDSL signal diminishes at a steep decline.

  • VDSL2 can deliver download and upload speeds as high as 10 Mbps; however, it is rare to achieve this maximum speed outside of lab conditions. In addition, VDSL2 supports higher rates than ADSL2+ with distances shorter than 3,000 feet.


  • R-ADSL (rate-adaptive digital subscriber line) has the same transmission rates as ADSL. However, unlike ADSL, R-ADSL can adjust the connection speed depending on the length and quality of the line.

Symmetrical DSL

In contrast to asymmetrical DSL, symmetrical DSL delivers equal bandwidth to both uploads and downloads. As a result, this technology works best for voice and video communication requiring high speeds in both directions. Therefore, symmetrical DSL tends to be used more often in business environments.

The most common type of symmetrical DSL is:

  • SHDSL (single-pair high-speed digital subscriber line) provides approximately equal download and upload speeds of 1.5 Mbps. This technology is a popular choice for private branch exchanges (PBXs), virtual private networks (VPNs), and web hosting.

Equipment Needed for DSL Internet

Not much equipment is required for DSL, and most of it is provided by your internet service provider (ISP). One thing to note: The equipment provided by your ISP is usually leased and must be returned to the provider should you terminate your contract. However, should you want to, you can purchase your own equipment. Here is what you will need:

  • DSL modem: This is a particular modem used for DSL only. It is the device that connects your computer to the internet.
  • Router: This piece of equipment enables all your wired and wireless devices to use the internet connection and allows them to communicate with each other. In some cases, an ISP will provide one box that serves as both a modem and router; however, they are still different technologies.
  • Line Splitter: This plugs directly into your phone line. It has two connections—one for the phone and the other for the DSL—and separates the data from the two, which speeds things up.

According to Plug Things In:

You don’t have to have an existing phone service, but you will need to have the phone jack and wiring. If you don’t have phone service, you’ll be given a dry lop or naked DSL line, which is essentially phone access without the dial tone. 

The Pros and Cons of DSL

As with any technology, there are both pros and cons when it comes to DSL.

DSL Pros

  • DSL is much faster than dial-up, and it is not much more expensive.
  • DSL is inexpensive—1.5 to 8 Mbps will cost in the neighborhood of $15 to $30 a month.
  • With DSL, you do not have to share your internet connection with your neighbors. So, no “peak usage periods.”

DSL Cons

  • DSL is distance sensitive; therefore, the farther you are from your ISP’s hub, the slower and poorer your connection will be. The maximum distance is about 18,000 feet (3.4 miles).
  • DSL service is not universally available. For example, you will not find many ISP provider hubs in very rural areas. So, due to the distance problems, DSL will not be possible.

Last Words

Digital subscriber line technology transforms a plain old telephone system (POTS) into a broadband communications link. DSL is fast and cheap and may just be the best technology for your home or business needs 

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