IX. Glossary and Index

2B1Q: The technology which is the basis for ISDN telephone service. [ VIII-A]

ADSL: Asymmetric Digital Subscriber Loop. A new telephone service which will provide very high data rates in one direction (to the subscriber) with a reverse channel which operates at much lower speeds. The prototypical application for ADSL is video on demand, where the high speed forward link provides the video signal and the reverse link a program selector. [ VIII-C]

ATM: Asynchronous Transfer Mode. A family of services based on cell relay technology and used to provide voice, video and data transmission. [ VIII-B]

Bandwidth: A measure of the data rate available over a given connection. Bandwidth is measured in bits per second (bps). [ II-B, III-C, VI-A, VI-B]

Bulletin board: An electronic messaging system, typically accessible by individual computers dialing in over standard voice-grade analog telephone lines. [ II-A]

Cable TV: The coaxial cable system used to carry cable television can be reconfigured to handle data, with rates currently as high as 10 million bps. [ VIII-A]

Cell Relay: A transmission technology based upon fixed length cells, as opposed to the variable length "frames" of Frame Relay. This approach allows for the efficient transmission of voice, video and data. [ VIII-B]

Client/server: A model for the provision of information services over a network. The client allows a user to makes queries and to display the results of those queries. The server manages some information resource on the network and provides responses to queries from remote clients. [ III-A, IV-C]

Computer interface: A component of a computer or router to which some external communications device can be attached. Examples include serial ports, to which modems can be connected, or synchronous interfaces, to which CSUs can be connected. [ VI-A, VIII-A]

Conditioned copper: Telephone lines which have been certified for high-speed data transmission. These are the basis of standard leased line data links. [ VI-B]

CoSN: The Consortium for School Networking. A group which seeks to facilitate access to networking technology and services for schools across the country. [ I-B]

CSU/DSU: Customer Service Unit/Data Service Unit. The line adapter used for high-speed leased lines (up to 1.5 million bps). [ VI-B]

DDS: Dataphone Digital Service (the name of a service originally supplied by AT&T). This is the digital service used for leased line transmissions. [ VIII-A]

DSU: Data Service Unit. The line adapter used for 56,000 bps leased lines. [ VI-B]

Ethernet: A commonly-used technology for local area networks. Ethernets provide speeds of 10 million bps. [ VII-B]

Fast packet service: A catch-all phrase used to denote any of the various successors to X.25 technology. Fast packet services cover a wide range of speeds, but typically involve data rates of 56,000 bps or higher. [ VIII-B]

FDDI: A LAN technology used on fiber optic links. FDDI provides a fixed rate of 100 million bps. Since FDDI fiber optic rings can be as large as 100 kilometers in circumference, it is possible to use FDDI to construct a Metropolitan Area Network. [ VIII-A]

Fiber optic cable: A technology which is supplanting copper wires as the favored means of providing network links with very high bandwidth. [ VIII-A]

File server: A machine which stores files for access from devices attached to a local area network. [ V-A, VI-A]

Frame Relay: A fast packet service offering speeds of 56,000 bps to 1.5 million bps. [ VI-D, VIII-B]

Freenet: One of a family of public access computing systems. [ III-B]

Gateway: A link which can pass electronic mail traffic from one system or network to another. [ II-A]

HDSL: High Density Subscriber Loop. A new signaling technology that allows for high-speed links over unconditioned copper. [ VIII-A]

Hybrid technology: A proprietary technology which provides unidirectional high-speed data links over cable TV systems. The back channel is provided through an independent telephone link. [ VIII-C]

Information server: A machine that distributes information to devices connected to a network. [ IV-C]

Internet: A set of interconnected computer networks which use a common protocol (see IP), which enables them to exchange information in a seamless manner. [ III-A]

Internet cloud: A metaphor for the multiconnected nature of the global Internet. [ IV-B, VII-D]

Interoperability: The ability of a system to allow for the simultaneous use of different types of hardware from a variety of different vendors. Systems like the Internet, which are governed by published public protocols, allow for a high degree of interoperability. [ I-C, II-A, IV-A]

IP: The Internet Protocol, a common public protocol which forms the basis for traffic on the Internet. [ III-A]

ISDN: Integrated Systems Digital Network. Telephone technology which can handle data and voice over the same digital circuit. Aggregate data speeds of 128,000 bps are possible with an ISDN Basic Rate Interface. [ VI-C, VIII-A]

LADS lines: Local Area Data Service. Private lines of unconditioned copper. Sites connected by LADS lines must be served by the same central office of your local telephone company. [ VI-B]

Leased line: A private line of conditioned copper leased from the telephone company to provide voice or data service. [ VI-B]

Line adapter: The electronics placed between a user's computing equipment or router and an external link. The simplest example of a line adapter is a modem. [ VI-A]

Local area network (LAN): A network which connects machines at a given site. LANs were originally introduced to facilitate the sharing of printers and mass storage devices. LAN architecture also facilitates the development of connectivity to metropolitan and wide area networks. [ III-C, V-A]

Local loop: The link from your local site to the nearest point of network connectivity. This element can be one of the most costly components of network connectivity. [ VII-C, VIII-A]

Mail host: A machine which provides you with access to electronic mail. Your mail host will have your name registered to provide you with an electronic address on the Internet. [ IV-C]

Metropolitan area network: That portion of the network which connects machines and LANs in your community. [ V-A, VII-C]

Modem: A device which enables computers to transmit data over telephone lines. [ II-B]

Network service provider: A company or service center which provides customers with access to the Internet through dialup telephone lines, leased lines or other connectivity options. [ IV-A]

NII: The National Information Infrastructure. A federal initiative under which the nation's data superhighway system will be developed. [ I-A]

Packet: The basic unit of data which flows across the Internet. Each packet contains address information (showing where it is coming from and where it is going), along with some fragment of data. The Internet routes individual packets, which are reassembled at their destination to produce a complete message. [ III-A, IV-B]

Packet services: Information services based upon the exchange of packets over the network. These services typically embody the client/server paradigm. [ IV-B]

PPP: Point to Point Protocol. A protocol which effectively replaces SLIP for dialup IP service. The present paper uses the term SLIP to cover both SLIP and PPP, although PPP is now typically preferred where it is available. [ IV-A]

Public domain software: Software which is distributed free of charge over the Internet. The quality of such software, which may be the product of some sponsored research project, is often extremely high. [ II-B]

Router: A device on the network which routes packets to their appropriate destination. The structure of the packets which routers handle is independent of the underlying medium (the type of wire, fiber or wireless link over which the packets are transmitted). [ IV-B, V-B]

Scalability: A ability of a system to accommodate increased usage, either from the same user population demanding a higher level or services, or through a greatly expanded user population, with no fundamental change in architecture. [ I-C, II-C, V-A, V-C]

Shareware: Software which is distributed over the network for a free trial period, but which requires registration and payment for regular use. Many individuals have attempted to build small businesses through this mechanism, and a few have been successful. The quality of available shareware varies widely. [ II-B]

Short-haul modem: A line adapter used to provide data service at 56,000 bps over short links of unconditioned copper. [ VI-B]

SLIP: Serial Line Internet Protocol. A protocol which allows one to extend Internet links over standard telephone lines. [ IV-A]

SMDS: Switched Multi-megabit Data Service. A fast-packet service that provides data rates ranging from 1.5 million bps to 45 million bps. [ VI-E, VIII-B]

SONET: Synchronous Optical Network. A family of data services for fiber optic links. Speeds range from 50 million bps to several billion bps. [ VIII-A]

Synchronous interface: A computer interface used with leased lines, Frame Relay, ATM and some ISDN services. Synchronous interfaces are more efficient but somewhat more complicated than the asynchronous interfaces (serial ports) used with standard modems. [ VI-B]

T1: A leased line providing service at 1.544 million bps. This is standard telecommunications transmission technology, available in lengths ranging from hundreds of feet to thousands of miles. Pricing is typically proportional to the length of the line. [ VI-B]

Terminal emulation: Software which enables a computer to perform the functions of a computer terminal. This software is commonly used for simple dialup network access. [ II-B]

Unconditioned copper: A private line using standard, or unconditioned, telephone cable. [ VI-B, VI-F, VIII-A]

Wide area network: That portion of the Internet which extends beyond your own metropolitan area. [ V-A, VII-D]

Wireless: A family of technologies which does not require any fixed wires for transmission. Common examples involve transmission via lasers, radio waves and microwaves. [ VIII-A]

X.25: The oldest of the packet-based services, originally used to link remote terminals to large central computers. [ VI-D]