Glossary of Internet Terms - FAQs -Internet Reference

A-F / G-L / M-R / S-Z

As you research solutions and compare services, use this handy reference guide to help understand the jargon.

ADSL - Asymmetric Digital Subscriber Line - A high-speed connection, usually to the Internet, using modems attached to twisted pair copper wiring. The download channel allows speeds from 1.5 Mbps to 9 Mbps and the upload channel allows you to transmit files between 16 kbps to 800 kbps. Speeds depend on distance from the telephone company’s central office, with approximately 3 miles being the furthest distance. Home and office users beyond this distance are generally unable to get ADSL.

ATM - Asynchronous Transfer Mode - This high speed network protocol is composed of 53 byte "cells" having 5 byte headers and 48 byte payloads. Because of its short packet length, it is ideally suited for real-time voice and video.

BANDWIDTH - Refers to the amount of information that can be transmitted over a connection, usually defined as bits per second bps - . Higher bandwidth allows more information to be transferred. A dial-up connection transmits up to 57,000 bits per second, but a T-1 almost 30 times as much, making it a much faster connection.

BAUD - The "baud rate" of a modem is how many bits it can send or receive per second. A 1200 bit-per-second modem actually runs at 300 baud, because it moves 4 bits per baud 4 x 300 = 1200 bits per second - . Baud is an outdated term, and has been replaced by "bits per second" or bps.

BIT - The basic unit of information in a base-2 or binary system: 0 or 1. 8 bits make up a byte. For the most part, bits are used to describe transmission speeds, whereas bytes generally refer to storage capacity.

BPS - Bits-Per-Second - A unit of connectivity or bandwidth. Most dial-up modems connect at 56,000 bps 56k - . A T-1 connects at 1.54 megabits per second.

BROADBAND - Short for "broad bandwidth." Any connection of 128 kb or faster, which is about 2 ˝ times faster than dial-up. It is measured in kilobits, megabits, or gigabits per second.

BYTE - The fundamental data unit of personal computers, a byte is eight contiguous bits. Usually byte is the basic unit of measurement for computer storage, storing the equivalent of one character. A kilo-byte is 1,000 bytes of data. A mega-byte is 1 million bytes.

CABLE MODEM - A modem that connects to a cable TV network providing Internet access, typically for homes, with speeds comparable to DSL. The download speed is generally higher than the upload speed. Since cable connections are shared, the actual speed varies, depending on the number of users attached to the network.

CIR - Committed Information Rate - - The minimum speed of the connection, most commonly used in frame relay circuits. See also MIR.

CLEC - Competitive Local Exchange Carrier - A Chicago-area CLEC leases circuits from SBC and sells them to their own customers.

CO - Central Office - A telephone company facility with circuit switches that terminate all the local access lines in a local geographic area. T-1 and other types of circuits connect the user to their central office and ultimately on to their ISP or other destination.

CO-LOCATION - aka "colo" or "co-lo" - A server located at a facility specifically designed to house public and private servers with a dedicated Internet connection, backup power and technical support. Co-lo is attractive to businesses and organizations with limited Internet connections or human resources to manage a public website or private Intranet.

CPE - Customer Premise Equipment - Equipment that connects a customer to an access circuit. This is usually a router, DSU or CSU, but can include telephones, modems, switches, hubs, terminals, servers, set-top boxes, etc.

CSU - Channel Service Unit - A device that connects a terminal to a digital line such as a T1 or DS-3. Similar to a modem, a CSU connects the port that connects the telco SBC SmartJack - and the router or computer. Sometimes referred to as a CSU/DSU. Data Service Unit -

Digital Gateway to IP - Digital Gateway to IP provides a seamless, dedicated connection to the Internet, utilizing available channels on the customer's channeled T1 local access. It allows increased usage of local access by providing multiple services over a single facility and the ability to design multiple DS0 channels on the T1 access for voice, data, and Internet.

DNS - Domain Name System - The system that translates Internet domain names into IP numbers. When you type into a browser, your request is converted to a digital address understood by Internet routers all over the world. A "DNS Server" is a server that performs this translation.

DS-3 - A high-speed circuit for Internet access or voice and video. It is the equivalent of 28 T1s, each of which may be used to connect to diverse locations, or the circuit can carry up to 45 Mbps of data between two locations.

DSL - Digital Subscriber Line - A popular alternative to Leased Lines and ISDN, being faster than ISDN and less costly than traditional Leased Lines. DSL moves data over regular phone lines. A common configuration of DSL allows downloads at speeds of up to 1.544 megabits per second, and uploads at speeds of 128 kilobits per second. This arrangement is called ADSL: Asymmetric Digital Subscriber Line. Another common configuration is symmetrical with speeds of 384 Kilobits per second in both directions. See also HDSL

DSU - Data Service Unit - A digital interface device that connects end user data communications equipment to the digital access lines, and which provides framing of sub-64Kbps customer access channels onto higher rate data circuits. A DSU may be combined with a CSU into a single device called a CSU/DSU.

E-Rate - Program of the Universal Service Administrative Company USAC - offering financial assistance to school and library technology programs. For more information:

Extranet - An intranet that is accessible to computers that are not physically part of a company’s own private network, but that is not accessible to the general public. For example, an extranet allows vendors and business partners to access private areas of a company web site. Users from outside the company’s network usually access the extranet using VPN.

FIREWALL - Hardware and/or software that separates a network into two or more parts for security purposes. The network behind the company’s firewall is protected from unauthorized outside access.

FTP - File Transfer Protocol - A very common method of moving files between two Internet sites. FTP is a way to login to another Internet site for the purposes of retrieving and/or sending files. FTP was invented and in wide use long before the advent of the World Wide Web and originally used from a text-only interface.

FRAC - A fractional connection or one that transfers a fraction of the maximum available bandwidth for the type of circuit, usually a T1 or DS-3.

FRAME CLOUD - Similar to the Internet, frame clouds are networks that are best suited for connecting far-away locations. Use frame to connect the home office in Chicago to the manufacturing facility in Atlanta or London.

FRAME RELAY - Similar to a T-1 connection, frame relay only guarantees a minimum connection speed or CIR. You can buy a frame circuit that will burst to a T-1’s 1.54mbps speed, but may sometimes transmit or receive at somewhat slower speeds, depending on the amount of traffic in the frame cloud.

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