A data over cable system adds to a cable television system a high-speed data communications path that is transparent to the Internet Protocol (IP), between subscriber locations and the cable operator's headend. The data over cable system includes not only the data communications elements but also the needed operations and business support elements for security, configuration, performance, fault, and accounting management. The cable modem typically is connected to a two-way cable RF path over a low-split HFC cable system. Thus, in the downstream direction (toward the subscriber), the cable modem receives signals in a predefined portion of the downstream passband, which will be between 50 MHz and a system-dependent upper limit that could be 750 MHz or more. In the upstream direction (away from the subscriber), the cable modem would transmit signals in a predefined portion of the upstream passband, which will be between 5 and 42 MHz.

A cable modem is a device that allows high-speed access to the Internet via a cable TV network.A cable modem will typically have two connections, one to the cable wall outlet and one to a computer. Cable modems allow consumers access to the Internet at higher speeds and at a fraction of the time it takes traditional telephone modems. This is true for two reasons: 1) broadband networks make the connection up to a hundred times faster, and 2) the service is "always on," meaning customers get the information they want, when they want it. Unlike telephone modems, cable modems allow consumers to keep their telephone lines open for voice conversations.

The CMTS is the unit that is purchased by and resides at the cable operator's facility, and acts as the connection between the cable network and the outside network. Cable modems are "certified" interoperable with each other while headend devices called Cable Modem Termination Systems (CMTSs) are qualified. CMTSs are termed "qualified" when they pass an interoperability test procedure similar to the modems. Certification provides the retail customer with the assurance that the cable modem complies with the DOCSIS specification and will interoperate with other certified modems and qualified headend systems. Qualification ensures the cable operator or broadband service provider that the headend equipment will interoperate with certified cable modems.

Cable operators may continue to provide their existing proprietary modem service, or they may replace their proprietary service with DOCSIS service, or operate both together in the same system.

As your cable operator transitions individual neighborhoods to CableLabs certified equipment, you will be contacted. In the meantime, your modem will operate as it always has.

DOCSIS 1.0 and 1.1 Specifications are posted on www.cablemodem.com. To summarize, DOCSIS 1.1 builds upon 1.0, but also includes the following features:
!P Quality of Service
!P Dynamic Services
!P Concatenation
!P Fragmentation
!P Payload Header Suppression
!P IP Multicast
!P CM Authentication
!P SNMPv3
!P View-based access control and management (VACM)
!P CM Account Management
!P Fault Management

ADSL, which stands for Asymmetric Digital Subscriber Line, is a broadband communication technology designed for use on regular phone lines. It has the ability to move data over the phone lines at speeds up to 140 times speedier than the fastest analog modems available today.

ADSL (Asymmetric Digital Subscriber Line) is a modem technology that transforms ordinary phone lines (also known as "twisted copper pairs") into high-speed digital lines for ultra-fast Internet access. ADSL also enables access to corporate networks for telecommuters, as well as exciting new interactive multimedia applications such as multiplayer gaming, video on demand and video catalogs.

-Simultaneous Internet and voice/fax capabilities over a single telephone line
-Uninterrupted, high-speed Internet access that's always on-line -Cost-effective solution for residential customers, telecommuters and small businesses
-Data Security that exceeds other technologies

Analog modems send their signals through the public switched telephone network, the same one that connects ordinary telephones. ADSL modems "piggyback" their signals on top of the voice signal. On the phone company's premises, the line gets split - the voice calls are sent to the public switched telephone network, and the data transmission goes to the Internet. This method moves data off the phone companies' lines and instead uses connections optimized for carrying Internet traffic.
Will it constantly connect near the maximum speed, or will it be like my 56K modem

At ADSL speeds, the limitations are much more the performance of the Internet server you're trying to reach and the amount of traffic on the Internet. The Internet is a loosely coupled network of computers that are transmitting data by different methods through different computers at different speeds, so the speed you receive data with an ADSL modem is limited by these factors.

ADSL provides always-on high-speed Internet access over a single dedicated telephone line; cable modems offer always-on high-speed Internet access over a shared cable television line. While cable modems have greater downstream (from the Internet into the home) bandwidth capabilities, that bandwidth is shared among all users in a neighborhood, and will therefore vary, perhaps dramatically, as more users in a neighborhood get online at the same time. Cable modem upstream (from the home to the Internet) traffic will in many cases be slower than ADSL, either because the particular cable modem is inherently slower, or because too many people in a neighborhood are trying to send or receive data at the same time. The big difference between ADSL and cable modems, however, is the number of lines available to each. There are no more than 12 million homes today that can support two-way cable modem transmissions, and while the figure is growing steadily, it will not catch up with telephone lines for many years. Only about 20 percent of homes are ready for cable modems now, compared to 50 to 60 percent of homes that are ready for ADSL service. Additionally, many of the older cable networks are not capable of offering a return channel; consequently, such networks will need significant upgrading before they can offer high bandwidth services.

That depends on whether the company that is currently providing your e-mail account also provides ADSL service. Web-based e-mail clients, like Netscape's Webmail or Hotmail, will not be affected by a change to ADSL service.