A Beginner's Guide to the Internet

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** A short list of networking terms ** asynchronous Transmission by individual bytes, not related to specific timing on the transmitting end. ARPANET Advanced Research Projects Agency Network. TCP/IP-based international network. BITNET Because It's Time Network. TCP/IP-based inter- national network. backbone High speed connection within a network which connects shorter (usually slower) branch circuits. bandwidth The difference, in Hertz (Hz), between the highest and lowest frequencies of a transmission channel; the greater the bandwidth the "faster" the line. baseband Characteristic of any network like Ethernet that uses a single carrier frequency and requires all stations attached to the network to participate in every transmission. baud Unit of measure of data transmission speed; usually bits/second. BBN Bolt, Beranek and Newman: the originators of packet switch nodes (PSNs). bps Bits per second. A measure of the rate of data transmission. bridge A device that acts as a connector between similar local area networks. Bridges operate at OSI Level 2, the Data Link Layer. broadband Transmission equipment and/or media capable of supporting a wide range of frequencies. Can carry multiple signals. broadcast A packet delivery system that delivers a copy of a given packet to all hosts that attach to it is said to broadcast the packet. CCITT Consultative Committee on International Telephony and Telegraphy. An international organization that sets the standards for interconnection of telephone equipment. client The user of a network service. coax Coaxial cable, comprised of a central wire surrounded by dielectric insulator, all encased in a protective sheathing. COM One of the top-level domains. Stands for commercial and includes commercial enterprises. For example: isis@sun.com CSNET Computer Science NETwork. datagram A self-contained package of data that carries enough addressing and routing information so that it can travel from source to destination without reliance on earlier exchanges between the source or destination and the transporting network. DCA Defense Data Network; a collection of admin- istratively and physically distinct networks, including the ARPANET and MILNET. DECnet A proprietary network for Digital Equipment Computers. dialup connection A connection between machines through a phone line. domain In the Internet, a part of the naming hierarchy. Syntactically, a domain name consists of a sequence of names separated by dots. dot address SEE INTERNET ADDRESS EDU One of the top-level domains. Stands for educational and includes educational institutions. For example: goodrich@rice.edu Ethernet A kind of network cable, or a network which conforms to IEEE standard 802.3. Designed by Xerox and char- acterized by 10 megabit/second baseband transmission over shielded coaxial cable. Ethernet meltdown An event that causes saturation or near saturation on an Ethernet. It usually results from illegal or misrouted packets and typically lasts only a short time. frame A self-contained package of data at the link layer. FTP File transfer protocl; a user-level protocol and and program that you can use to transfer files over the network. gateway A device that acts as a connector between two logically separate networks. It has interfaces to more than one network and can translate the packets of one network to another, possibly dissimilar, network. GOV One of the top-level domains. Stands for gov- ernment and includes governmental organizations. For example: smith@nssdca.gsfc.nasa.gov half duplex Transmission link that allows only non-simultaneous two-way communications. HEPnet High Energy Physics network. IGP Interior Gateway Protocol. The generic term applied to any protocol used to propagate network reach- ability and routing information within an autonomous system. Although there is no Internet standard IGP, RIP is among the most popular. IMP Interface Message Processor. Former name of packet switches used in the ARPANET. An IMP is now called a Packet Switch Node (PSN). internet Physically, a collection of packet switching networks interconnected by gateways along with protocols that allow then to function logically as a single, large, virtual network. When written in upper case, Internet refers specifically to the DARPA Internet and the TCP/IP protocols it uses. Internet The collection of networks and gateways, including the ARPANET, MILNET, and NSFnet, that use the TCP/IP protocol suite and function as a single, cooperative virtual network. The Internet reaches many univer- sities, government research labs, and military installations. Internet address The 32-bit address assigned to hosts that want to participate in the Internet using TCP/IP. interoperability The ability of software and hardware on multiple machines from multiple vendors to communicate meaningfully. IP Internet Protocol. The Internet standard protocol that defines the Internet datagram as the unit of information passes across the Internet and provides the basis for the Internet connectionless, best- effort packet delivery service. IP datagram The basic unit of information passed across the Internet. An IP datagram is to the Internet as a hardware packet is to a physical network. It contains a source and destination address along with data. IP/TCP Alternate name for TCP/IP ISO International Standards Organization; responsible for publishing the Open System Interconnection Reference Model. kernal The level of an operating system or networking system that contains the system-level commands or all of the functions hidden from the user. In a UNIX system, the kernal is a program that contains the device drivers, the memory management routines, the scheduler, and system calls. This program is always running while the system is operating. LAN Local Area Network. A high speed network connecting machines at one site. mail bridge Used loosely to refer to any mail gateway. mail gateway A machine that connects to two or more electronic mail systems (especially dissimilar mail systems on two different networks) and transfers mail messages among them. MIL One of the top-level domains. Stands for military and includes military organizations. For example: clyde@hqafsc.af.mil modem A device that enables a machine or terminal to es- tablish a connection and transfer data through tele- phone lines. narrowband Sub-voice-grade channels characterized by data speeds between 100 and 200 bits/second. NCP Network Control Protocol or Program; the original host-to-host protocol for the ARPANET. In 1983, it was replaced by TCP/IP. NET One of the top-level domains. Stands for network and includes network service centers, network information centers, and other organizations that have a hand in network management. network A group of machines connected together so they can transmit information to one another. There are two kinds of networks: local networks and remote networks. network path A series of machine names used to direct electronic mail from one user to another. NSFnet National Science Foundation Network. TCP/IP-based network. octet An octet is 8 bits; this term is used in networking (rather than byte) because some systems have bytes that are note 8 bits long. ORG One of the top-level domains. Encompasses nonprofit organizations. OSI Open Systems Interconnection. Proposed 7-layer network which will allow any OSI-compliant system to communicate with any other OSI-compliant system. packet A unit of data sent across a packet switching network. packet switching Data transmission technique in which data is seg- mented and routed in packets. protocol A formal set of rules governing the format, timing, error control of transmissions on a network. The protocol that networks use to communicate with each other. IP, DECnet and UDP are examples. PSN Packet Switch Node. repeater A hardware device that connects identical networks. Repeaters operate at OSI Level 1, the Physical Layer. RFC Request for Comments; started out as actual comments about networking. Now RFCs are the published mech- anism for new networking standards for the TCP/IP community. route The path that network traffic takes from its source to its destination. routed Route Daemon. A program that runs under 4.3BSD UNIX to propagate routes among machines on a local area network. It uses the RIP protocol. Pronounced "route-d". router A hardware and software device that connects hosts on different networks. Routers operate at OSI Level 3, the Network Layer. routing The process of selecting the correct path (circuit) for a transmission over a network. RS-232, RS-449 Cables used for connecting the components of a network; network media. server A provide of network service. SMTP Simple Mail Transfer Protocol. The Internet standard protocol for transferring electronic mail messages from one machine to another. SNA System Network Architecture; a proprietary protocol developed by IBM. SNA does not interoperate with the TCP/IP Internet. synchronous Data communications in which transmissions are sent at a fixed rate, with the sending and receiving devices synchronized. T1 AT&T term for digital circuit carrying transmissions at a rate of 1.544 megabits/second. T3 Transmission rate on this type of circuit is 44.736 megabits/second. TAC Terminal Access Controller. A program and piece of hardware that connects terminals to the Internet, usually using dialup modem connections. TCP Transmission Control Protocol. The Internet standard transport level protocol that provides the reliable, full duplex, stream service on which many applica- tion protocols depend. TELENET A public packet switched network using the CCITT X.25 protocols owned and operated by GTE. TELNET The Internet standard protocol for remote terminal connection service. twisted pair Cable made up of a pair of insulated copper wires wrapped around each other to cancel the effects of electrical noise. user-level protocols Protocols, such as TELNET, SMTP, and FTP, which allow you to perform operations or applications on the network. UUCP UNIX to UNIX Copy Program. virtual circuit A network service that allows two processes to communicate as if they were directly connected to each other. A virtual circuit is similar to a UNIX pipe. WAN Wide area network. X.25 The CCITT standard protocol for transport level network service. Originally designed to connect terminals to computers, X.25 provides a reliable, stream transmission service that can support remote login. It is possible to run Internet protocols over an X.25 network. X.25 is most popular in Europe. X.400 The ISO protocol for electronic mail that is expected to become widely accepted. Work is underway to make Internet mail systems interoperate with X.400. XNS Xerox Network Systems; a proprietary network devel- oped by Xerox corporation. yellow pages A directory of usernames, passwords, and machine names on a local network that provides automatic machine addressing. The yellow pages decreases the need for a "host table" file.