Glossary of Terms

56K: The term 56K refers to a new generation of modems that improve the speed of communication between personal computers and the Internet. The previous speed standard of v.34 provided communication at speeds as high as 33,600 bits per second (bps). The new 56K modems increase that speed to a theoretical maximum of 57,600 or 56 Kbps. In the past, two different technologies emerged, enabling 56K communication: K56flex and x2. They have been replaced by a new, international standard for 56K data communications known as v.90.

Asymmetric Digital Subscriber Line (ADSL): ADSL is the most popular form of DSL technology which typically emphasizes high bandwidth downstream (e.g. up to 6.144Mbps) and lower bandwidth upstream (e.g. 640kbps)

Bandwidth: The capacity for or measure of data that can be sent or received in a given time. For example, the bandwidth of a typewriter "maxes out" at about 100 words per minute, while a laser printer can crank out six pages per minute. In more realistic terms, an analog modem has an absolute maximum capacity of 7000 characters of text per second, while DSL allows up to 7,168,000 characters of ordinary text (including spaces) per second. The difference is one of bandwidth.

Broadband: A term for high-speed, high-capacity Internet and data connections.

Bit: The smallest measure of computer data size.

Byte: 8 bits. One character of text is one byte, so the alphabet is 26 bytes.

Central Office (CO): A facility that contains the lowest level of switches that comprise the public telephone network.

Dial-Up Connection: A type of data connection that is made by using a modem to connect to the public telephone network, to connect to the Internet, for example. Because dial-up access uses normal telephone lines, the quality of the connection is not always good and data rates are limited.

Digital Subscriber Line (DSL): An access technology that calls for modems on either end of a copper twisted-pair wire to deliver data, voice and video information over a dedicated digital network.

Domain Name: A name that identifies one or more IP addresses. For example, the domain name microsoft.com represents about a dozen IP addresses. Domain names are used in URLs to identify particular Web pages. For example, in the URL http://www.pcwebopedia.com/index.html, the domain name is pcwebopedia.com.

Domain Name Servers (DNS): Short for Domain Name System (or Service), an Internet service that translates domain names into IP addresses. Because domain names are alphabetic, they're easier to remember. The Internet however, is really based on IP addresses. Every time you use a domain name, therefore, a DNS service must translate the name into the corresponding IP address.

Downstream Rate: The rate, measured in Megabytes or Kilobytes, in which a computer receives data over DSL lines

Ethernet: A local-area network (LAN) protocol that connects all office computers and supports data transfer rates of 10 Mbps.

Dynamic IP Address: A network address assigned to a machine, account or user for only a single online session.

Fiber Optics: A technology that uses glass (or plastic) threads (fibers) to transmit data. A fiber optic cable consists of a bundle of glass threads, each of which is capable of transmitting messages modulated onto light waves. Fiber optic cables have a much greater bandwidth than metal cables.

HDSL: High Bit-Rate Digital Subscriber Line (HDSL) is generally used as a substitute for T1/E1.

Hosting: A service that allows customers to place their own content on the public Internet's World Wide Web.

Hub: A common connection point for devices in a network.

Internet Service Provider (ISP): A company that provides Internet access services.

IP Address: A unique number given to an individual machine, account or user for the purpose of identifying them on a TCP/IP network.

Kilobyte: One thousand bytes of computer data.

Kbps: Abbreviation for kilobits per second. A measure of the data transfer rate for a network connection.

Local Area Network (LAN): A type of network covering a limited area, in which computers and other devices are attached to a common medium.

Local Loop: The line from a subscriber's premises to the telephone company central office.

Megabit: A unit of size that means 1000 kilobytes (1 million bytes).

Mbps: Abbreviation for megabits per second. A measure of the data transfer rate for a network connection.

Modem: Contraction for modulator/demodulator; a modem converts the digital data from a computer (or fax machine, or whatever) into a form suitable for transmission over the public telephone network. Analog modems are used by millions of users today to connect to the Internet.

Network: A system of interconnected components (i.e. the computers, the wires or wireless signals) that enable them to communicate.

Network Card: A piece of hardware that fits into a computer and allows it to communicate with other computers across a network.

POTS: Plain Old Telephone Service.

POTS splitter: A Plain Old Telephone Service (POTS) splitter, also known as a low-pass/high-pass filter, separates the voice and data portions of the DSL line. Current DSL technology requires two POTS splitters: one in our central office and one in the customer's premises.

RADSL: Rate Adaptive Digital Subscriber Line (RADSL) is any rate adaptive DSL modem.

Repeaters or Amplifiers: A network device used to regenerate or replicate a signal. Repeaters are used in transmission systems to regenerate analog or digital signals distorted by transmission loss.

Router: A device that connects any number of LANs.

SDSL: Symmetric Digital Subscriber Line (SDSL) is a 2-wire implementation of (HDSL).

Static IP Address: A network address permanently assigned to an individual machine, account, or user.

TCP/IP or Transmission Control Protocol/Internet Protocol: The language of computers on the Internet (and many private networks). Any machine with access to the Internet has a copy of the TCP/IP program.

Twisted Pair: Telephone system cabling that consists of copper wires loosely wrapped around each other for the purpose of canceling background noise.

Upstream Rate: The rate, measured in Megabytes or Kilobytes, in which a computer transfers or sends data over DSL lines.

WAN: Wide Area Networks.

World Wide Web: A global collection of public and private documents, multimedia files and other network resources and activities which is available to anyone who can access the Internet and has Web browser software.

XDSL: Refers to the family of digital subscriber line technologies, such as ADSL, HDSL and RADSL.