DSL Facts and Information

Consumer Information | Internet Access

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What is Digital Subscriber Line (DSL)? Digital Subscriber Line is a technology for bringing high-speed and high-bandwidth, which is directly proportional to the amount of data transmitted or received per unit time, information to homes and small businesses over ordinary copper telephone lines already installed in hundreds of millions of homes and businesses worldwide. With DSL, consumers and businesses take advantage of having a dedicated, always-on connection to the Internet.

What is the Difference between DSL vs. Cable Modem?

Cable modem services offer shared bandwidth between your and your neighbors. Your speed will vary with how many people are on the cable modem network, which may be a disadvantage. With DSL service, you have a dedicated connection to your home.

How Does DSL Service Work?

Traditional phone service connects your home or business to a telephone company office over copper wires that are wrapped around each other. The wires are called twisted pair. The digital modem, which may be purchased or rented, — located at your location — accesses the local telephone companies’ central office where a Digital Subscriber Line Access Multiplexer, which translates your DSL signal, has been installed. The signal is then transmitted from the copper telephone line onto a network backbone, and directed to the ISP’s location, where the ISP verifies the access to the network and delivers users to the Internet through the ISP’s relationship with a backbone network provider.

What Types of DSL Service are Available?

There are currently at least six different types of DSL. They are Asymmetric Digital Subscriber Line (ADSL), Symmetric Digital Subscriber Line (SDSL), ISDN Digital Subscriber Line (IDSL), High-bit-rate Digital Subscriber Line (HDSL), Very high-bit-rate Digital Subscriber Line (VDSL), and Rate-Adaptive Digital Subscriber Line (RADSL). Each one has different technical ranges, capabilities, and limitations.

ASDL
ADSL (Asymmetric Digital Subscriber Line) has different speed in both directions. Basically, with ASDL, the rate at which information transfers down is different (and usually higher) than the rate at which speed transfers up. ASDL is the most typical type of DSL found in home use because most users need to download faster than they need to upload since they do more of the former. This allows you to put most of the speed into surfing and downloading information at fast speeds.

SDSL
SDSL (Symmetrical Digital Subscriber Line) has synchronous speeds. Information transfers down at the same rate that is transfers up. SDSL is a usual choice for businesses due to multiple computers usually accessing the same connection. With multiple users using an Internet connection, you can use more transfer up than that which would get used in a typical home setting where only one or a few computers would be accessing the single connection.

IDSL
IDSL (IDSN Digital Subscriber Line) also offers symmetrical transfer speeds at a fixed speed (thus limiting the choice of your speed rate to 144 Kbps). IDSL is a popular choice for users in rural areas where they are two far from a switch to obtain ADSL or SDSL, but want something faster than a V.90 connection offered by most dial up services.

HDSL
HDSL (High-bit-rate Digital Subscriber Line) also offers symmetrical speeds. This is a service usually limited to commercial zones and is seen as an alternative type of T1 data transfer service. HDSL requires two phone lines to work.

VDSL
VDSL (Very High-bit-rate Digital subscriber Line) is the highest speed DSL connection, but with limited range. In order to use a VDSL connection, you need to be within a short distance from the central line.

RADSL
RADSL (Rate-Adaptive Digital Subscriber Line) is an ADSL technology that dynamically adjusts transmissions based on the line quality and the distance the transfer is traveling. RADSL, like ADSL, allows transfers to occur at different speeds in both directions.

What are the Advantages to having DSL?

Faster Speed
DSL and cable modems are much faster than analog modems. Different varieties of DSL provide different maximum speeds, from twice as fast to approximately 125 times faster than standard dial up services.

Always On
Your DSL or CM (cable modem) connection is always there. There’s no need to dial up and listen to your modem squawk. And there’s no frustration about the line dropping.

Flat Rate Service
DSL and CM typically don’t have usage-sensitive pricing, which means that the connection can be used any time for as long as you need without incurring usage charges. Technical advances enable prices to fall and gain in power, facilitating the creation and operation of global networks.

What are the Disadvantages to having DSL?

Distance
Distance between the user’s premises and phone company’s central office or cable installation is a primary factor deciding who can get these services and the speed of these services. Rural users usually can’t access ADSL and must an IDSL alternative if one is available.

Limited Competition
External providers must coordinate with local phone or cable companies to provide service, which may cause installation delays.

Security
Because DSL is always on, you may want to check with the provider about security vulnerability and precautions. DSL users should make sure they have a firewall software installed and protecting their system.