Cable modems and residential DSL are two of several high-speed Internet technologies grouped under the term "broadband services." While the whole of broadband services can be either one-way or two-way, and wired or wireless, this report is concerned primarily with two-way, consumer-oriented services predominated by cable modems and residential DSL.
Why would someone want broadband services? Convenient, high-speed delivery. This is desirable for several reasons:
Broadband services can provide multiple channels of data over a single communications medium, such as a telephone or cable TV line. This means you can use one line for multiple services such as voice (telephone) or other (fax) analog signals, and data (digital movies or your computer) at the same time. Depending on the condition and age of your house's present phone lines, rewiring or additional phone or cable lines are often unnecessary.
Broadband offers an affordable alternative to regular dial-up modems. Subscription dial-up services, for which a modem is required, need to be initiated--you need to dial up and log on each time you want to access the Internet. And if you wish to use your telephone and your computer at the same time, you may need a separate phone line.
Broadband services don't need to go through a lengthy connection process. Instead, they offer a continuous/persistant connection to the Internet, sometimes referred to as "always on." Broadband services mean you're connected to the Internet whenever your computer is turned on.
The cable system was designed to carry television programming to subscribers' homes. With the addition of a cable modem, cable services can now offer broadband access to Internet services.
With cable, all homes within the network's community share available bandwidth. Each local cable controller, or "headend," serves up to 2,000 households in one local community. The cable network is shared by all homes that are active at any moment in time. (Subscribers are considered "active" whenever they request or receive information. They are not active, with regard to network usage, while reading or composing email, scanning a web page, or if their computer is turned off.) For example, if many homes are actively be using the Internet at 8 P.M., service is divided among all active requests at that moment. This usually results in slowed services, compared to the number of subscribers surfing, say, at 4 A.M.
DSL is a newer technology that may allow an ordinary phone line to be "split" into two parts: the traditional voice/fax (analog) services, and a new digital data line. These two parts can be used simultaneously.
DSL services connect the subscriber's home directly to the local telephone company's Central Office (CO). This point-to-point connection may not exceed 18,000 feet, limiting DSL's effective range. Internet Service Providers (ISPs) offer DSL Internet access accounts using telephone company lines. With the addition of a DSL modem, home (and "small business") subscribers can now get broadband access to Internet services over their existing phone lines.
DSL comes in several forms. xDSL is a generic term referring to any of these forms. ADSL, or Asymmetric DSL, offers higher speed (bandwidth) usually coming into a home than the speed of signals going out. SDSL, or Symmetric DSL, offers equal bandwidth coming and going.
Many promises and perils of a networked world are still to be realized. As thousands of new subscribers sign up every day, the complexity and diversity of our world increases. New opportunities for good also bring risks.
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