| Comparing DSL and Cable Modem Services |
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| Digital
Subscriber Line (DSL) is a wireline transmission technology that brings
data and information faster over copper telephone lines already installed
in homes and businesses. Traditional phone service connects your home or
business to a telephone company office via copper wires. A DSL modem
accesses the local telephone company's central office where a DSL Access
Multiplexer (DSLAM) has been installed. The DSLAM then transmits the
signal from the copper telephone line onto a network backbone, and
eventually to the Internet. With high-speed Internet access that uses DSL
transmission technology, there is no need to "dial in" to a telephone
number as with a traditional modem. This service allows consumers and
businesses to have an "always-on" dedicated connection to the
Internet. The following are types of DSL transmission technologies that may be used to provide high-speed Internet access: > Symmetrical Digital Subscriber Line (SDSL) - used typically for business applications such as video conferencing. The traffic from the user to the network is upstream traffic, and from the network to the user is downstream traffic. When the data rate in both directions is equal, it is called a symmetric service. > Asymmetrical Digital Subscriber Line (ADSL) - used primarily by residential users who receive a lot of data but do not send much, such as Internet surfers. ADSL provides faster speed in a downstream direction (from the telephone central office to the customer's premises) than upstream (from customer's premise to the telephone central office). When the upstream data rate is lower than the downstream rate, it is called an asymmetric service. > ISDN Digital Subscriber Line (IDSL) - provides symmetrical connection with Integrated Services Digital Network (ISDN), and is designed to extend DSL to locations with a long distance to a telephone central office. > High-data-rate Digital Subscriber Line (HDSL) - provides fixed symmetrical high speed access at T1 rate (1.5 Mbps), and is designed for business purposes. > Very high-data-rate Digital Subscriber Line (VDSL) - provides both symmetrical and asymmetrical access with very high bit rate over the copper line. Deployment is very limited at this time. |
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DSL Compared to ISDN
ISDN is an affordable way to have rapid access to the Internet. It is a digital technology that is widely available and is an option for businesses located in areas not yet served by DSL. DSL and ISDN are different transmission technologies, yet both offer many of the same higher speed benefits to consumers. DSL offers potentially higher transmission speeds as well as a choice of connection speeds. ISDN is presently more widely available than DSL. DSL is an always-on service while ISDN requires dialing into a service provider's network. If DSL transmission technology is not available in your area, ISDN may serve as an acceptable substitute for use in providing high-speed Internet access. Differences Between DSL and Cable Modem Service High-speed Internet access that uses cable modems offers shared bandwidth or speed among neighbors on the same cable system. Speed is asymmetric and will vary depending on the number of people on the network. With high-speed Internet access that uses DSL service, you have a dedicated connection to your home. In most cases, however, the performance of DSL-based service depends on the distance between end user and phone company central office. Today, high-speed Internet access provided using either DSL or cable modems typically is offered with a pricing plan that allows access to the service for as long as needed without incurring additional usage charges. Many phone and cable companies are offering bundled packages of various services (such as telephone, cable, and high-speed Internet access) to lower costs to consumers. High-speed Internet access using cable modems is targeted towards residential use while DSL-based service is targeted towards residential and business uses. Advantages and Disadvantages of DSL vs. Cable Modems High-speed Internet access provided using DSL and cable modems is much faster than dial-up modems, however their speeds differ. The distance between the user's premises and the phone company's central office is a primary factor in deciding if DSL-based Internet access service is available and its speed. In contrast, the speed of cable modem-based Internet access service does not depend on the distance from cable company to end user. Because DSL transmission technology must access the local phone company's central office, competitive providers using DSL technology must coordinate with local phone companies to provide service. Because both versions of high-speed Internet access (DSL and cable modem) are always on, you may want to check with the provider about security precautions. DSL and cable modem equipment are generally based on standard specifications and required certification, however, the best advice is to check with the service provider prior to purchase of such equipment. Different varieties of DSL transmission technology provide different maximum speeds, from twice as fast as analog modems to higher than 100 times faster. Getting DSL or Cable Modem Service Contact a provider in your geographical area. The provider may be your local telephone service provider or one of its competitors (for DSL-based Internet access), or your local cable company (for cable modem-based Internet access). There are different high-speed Internet access services available, and the equipment of one provider may not be interoperable in another area or with another provider. Check with your service provider for technical compatibility. Prior to getting high-speed Internet access service, residential users should check with the service provider to find out the minimum data speed that the provider can deliver. Consumers should also check the cost of the service. After receiving the service, contact the provider and make it aware of any adverse experience(s) you encounter. Investigate obtaining service through a different provider if you are not pleased with your current service or provider. |
| This fact sheet
provides an overview of DSL and cable modem services and compares the
advantages and disadvantages of these two types of high-speed Internet
access. |
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| Related Sites: Broardband Cable Modem Services Forum |
| This document is
provided solely for educational and informational purposes and does not
constitute legal advice. |