Technical Library

Internet User's Glossary

PC Webopaedia

Whatis?com

A


• Access
  Entry to or communication with a particular object, such as operating system, specific files or accounts. Remote Access is the service that provides the access to these systems, files, and/or accounts.
  
  
• Access Line
  A communications line (e.g., circuit) interconnecting a Frame-Relay-compatible device (DTE) to a Frame Relay switch (DCE).
  
  
• Account
  An entity which is established as an authorized user of the system. Each Remote Access user requires an account (ppxxxxxx) in order to establish a connection to the service.
  
  
• ACK
  From the ASCII mnemonic for 0000110: Acknowledge. Used to register one's presence. Ping is an application that performs an ACK function. See also Ping.
  
  
• Address Resolution
  A means for mapping Network Layer addresses onto media-specific addresses. This is what happens when you type in a host name, and your DNS server looks up the corresponding IP address.
  
  
• AMI - Alternate Mark Inversion
  A bipolar coding scheme in which successive ones (marks) must alternate in polarity (alternate between positive and negative).
  
  
• Analog
  Not digital. A continuous wave or signal (such as the human voice).
  
  
• Analog Loopback
  A testing technique which isolates faults in transmission equipment by performing a loopback on the data at the analog (line) side of the modem.
  
  
• Analog Transmission
  The transmission of a continuously variable signal, as opposed to a discrete (digital) one.
  
  
• Anonymous FTP
  Anonymous FTP allows a user to retrieve documents, files, programs, and other archived data from anywhere in the Internet without having to establish a userid and password. By using the special userid of "anonymous," the network user will bypass local security checks and will have access to publicly accessible files on the remote system. Most anonymous FTP sites require a valid Internet address for the password.
  
  
• ANSI - American National Standards Institute
  ANSI sets the standards for the US computer industry, and participates in defining network protocol standards.
  
  
• Application
  A computer program that performs a certain task.
  
  
• Application Layer
  The top-most layer in the OSI Reference Model providing such communication services as electronic mail and file transfer.
  
  
• AR - Access Rate
  The data rate of the user access channel. The speed of the access channel determines how rapidly (maximum rate) the end user can inject data into a Frame Relay network.
  
  
• Archie
  A system to automatically gather, index and serve information on the Internet. The initial implementation of archie provided an indexed directory of filenames from all anonymous FTP archives on the Internet. Later versions provide other collections of information. See also: archive site, Gopher, Prospero, Wide Area Information Servers.
  
  
• Archive Site
  A machine that provides access to a collection of files across the Internet. An "anonymous FTP archive site," for example, provides access to this material via the FTP protocol. See also: anonymous FTP, archie, Gopher, Prospero, Wide Area Information Servers.
  
  
• ARP - Address Resolution Protocol
  Protocol used to translate an IP address into an Ethernet or hardware address.
  
  
• ASCII - American Standard Code for Information Interchange
  An eight bit code for character representation; includes seven bits plus parity. It is the widely accepted code to represent alphanumeric information.
  
  
• ASCII Art
  The fine art of drawing diagrams using the ASCII character set (mainly `|', `-', `/', `\', and `+'). Also known as `character graphics' or `ASCII graphics'; see also {boxology}. Here is a serious example:
  

      o----)||(--+--|<----+   +---------o + D O
        L  )||(  |        |   |             C U
      A I  )||(  +-->|-+  |   +-\/\/-+--o -   T
      C N  )||(        |  |   |      |        P
        E  )||(  +-->|-+--)---+--)|--+-o      U
           )||(  |        |          | GND    T
      o----)||(--+--|<----+----------+
  
  A power supply consisting of a full wave rectifier circuit
      feeding a capacitor input filter circuit
  

  
  
  
• ATM - Asynchronous Transfer Mode
  The CCITT standard for cell relay wherein information for multiple types of services (voice, video, data) is conveyed in small, fixed-sized cells.
  
  
• Autoexec.bat
  The AUTOEXEC.BAT file resides on all PCs and contains a series of commands that are executed when the computer starts up. This file includes the path command that points to the NETMANAG directory where all of the Chameleon applications reside.
  
  
  B
  
  
• Backbone
  The top level in a hierarchical network. Stub and transit networks which connect to the same backbone are guaranteed to be interconnected.
  
  
• Backup
  Backup is the process of preserving copies of files on a different drive, directory, or media, to protect against the destruction or loss of the original files in the event of a hardware or system failure.
  
  
• BACP - Bandwidth Allocation Control Protocol
  The set of rules that manage bandwidth over PPP dynamic multilink connections.
  
  
• Balanced
  A transmission line in wich voltages on the two conductors are equal in magnitude, but opposite in polarity with respect to ground (with opposite polarities).
  
  
• Balanced Configuration
  In HDLC, a point-to-point network configuration with two combined stations.
  
  
• Bandwidth
  The range of frequencies, expressed in Kilobits per second, that can pass over a given data transmission channel within a Frame Relay network. The bandwidth determines the rate at which information can be sent through a channel – the greater the bandwidth, the more information that can be sent in a given amount of time.
  
  
• Bandwidth Reservation
  In circuit-switched lines, a feature in which call bandwidth can be reserved for high-bandwidth or high-priority calls.
  
  
• Baud
  Unit of signalling speed equivalent to the number of discrete conditions or events per second. If each signal event represents only one bit condition, baud rate equals bps (bit per second).
  
  
• B Channel - Bearer Channel
  The 64 Kbps B channels can carry high quality audio, video, or data communications. In addition, the B channels can be bonded together for increased bandwidth. B channels can be used for circuit-switched voice or for circuit-switched or packet-switched data.
  
  
• BERT - Bit Error Rate Test
  A test for digital lines which involves looping a line and sending a test pattern. Data returning is compared to the sent data to check for errors. Depending on the "Test Pattern" used, BERTs may or may not uncover problems. A line which only has occasional problems will need a BERT of sufficient time duration to catch that intermittent solution. A 5 minute BERT will only catch severe problems.
  
  
• BGP - Border Gateway Protocol
  A routing protocol used to exchange routing information between Internet Service Providers. BGP is an exterior gateway protocol defined in RFC 1771. Its design is based on experience gained with EGP, as defined in RFC 904, and EGP usage in the NSFNET Backbone, as described in RFCs 1092 and 1093.
  
  
• Binary File
  A file that contains codes which are not part of the ASCII character set. A binary file can contain any type of information that can be represented by an 8 bit byte - a possible 256 values.
  
  
• BIND - Berkeley Internet Name Domain
  Implementation of a DNS server developed and distributed by the University of California at Berkeley. Many Internet hosts run BIND, and it is the ancestor of many commercial BIND implementations.
  
  
• BinHex (BINary HEXadecimal)
  A method for converting non-text files (non-ASCII) into ASCII. This is needed because Internet e-mail can only handle ASCII text.
  
  
• Bipolar
  A signalling method (used in T1/E1) wich represents a binary "1" by alternating positive and negative pulses, and binary "0" by absence of pulses.
  
  
• Bit
  A contraction of "Binary Digit," the smallest unit of information in a binary system. A bit represents either a one or zero ("1" or "0").
  
  
• BITNET - Because It's Time NETwork
  An academic computer network based originally on IBM mainframe systems interconnected via leased 9600 bps lines. BITNET has recently merged with CSNET, The Computer+Science Network (another academic computer network) to form CREN: The Corporation for Research and Educational Networking.
  
  
• Bit Rate
  The capacity of a digital channel. ISDN calls are set up at a given bit rate, either 64Kbps or 56Kbps. The bit rate cannot be changed during a call.
  
  
• Black Hole
  Routing term for an area of the network where packets enter but do not emerge, due to observe conditions or poor system configuration within a portion of the network.
  
  
• BOC - Bell Operating Company
  More commonly referred to as RBOC for Regional Bell Operating Company. The local telephone company in each of the seven U.S. regions.
  
  
• Bonding
  The use of both B-Channels at once to connect to a remote ISDN host. Not to be confused with MPPP.
  
  
• Bounce
  The return of a piece of mail because of an error in its delivery.
  
  
• BRI - Basic Rate Interface
  BRI enables the use of existing copper telephone wire (a single pair of twisted wires) to obtain ISDN service consisting of two 64 Kbps B channels and one 16 Kbps D channel.
  
  
• Bridge
  A device which routes network traffic from one interface to another. It does this at the hardware layer by identifying the hardware (e.g., ethernet, token ring, etc.) addresses and directing traffic based on the destinations.
  
  
• BRITE - Basic Rate Interface Transmission Extension
  A technology where ordinary T-1 trunks are used to extend ISDN service.
  
  
• Broadcast
  A special type of multicast packet which all nodes on the network are always willing to receive.
  
  
• Broadcast Address
  An address reserved for sending to all stations on a network simultaneously.
  
  
• Brouter
  A device which bridges some packets (i.e., forwards based on datalink layer information) and routes other packets (i.e., forwards based on network layer information). The bridge/route decision is based on configuration information. See also: bridge, router.
  
  
• Browser
  A World Wide Web client - that is, a software package that permits you to look around the World Wide Web (WWW).
  
  
• Buffer
  A storage device. Commonly used to compensate for differences in data rates or event timing when transmitting from one device to another.
  
  
• Bulletin Board System
  A computer, and associated software, which typically provides services or activities of interest to the bulletin board system's operators. Although BBS's have traditionally been the domain of hobbyists, an increasing number of BBS's are connected directly to the Internet, and many BBS's are currently operated by government, educational, and research institutions. See also: Internet, Usenet.
  
  
• Burstiness
  In the context of a Frame Relay network, data that uses bandwidth only sporadically; that is, information that does not use the total bandwidth of a circuit 100 percent of the time. During pauses, channels are idle and no traffic flows across them in either direction. Interactive and LAN-to-LAN data is bursty in nature, because it is sent intermittently, and in between data transmissions the channel experiences idle time waiting for the DTEs to respond to the transmitted data.
  
  
  C
  
  
• CENTREX
  A service provided by a central office that provides a virtual PBX to a set of extensions. It offers features such as transfer, conference, and forward within that set of extensions.
  
  
• Channel
  Generically refers to the user access channel across which data travels.
  
  
• CIDR - Classless Inter-Domain Routing
  Network addressing scheme that allows for the aggregation of network routes to reduce the load on Internet routers.
  
  
• CIR - Committed Information Rate
  The committed rate (in bits per second) at which the ingress access interface trunk interfaces, and egress access interface of a Frame Relay network transfer information to the destination Frame Relay end system under normal conditions. The rate is averaged over a minimum time interval Tc.
  
  
• CIX - Commercial Internet Exchange
  One of the Internet exchange points where different Internet Service Providers agree to exchange routing information. PSINet was one of the co-founders of this exchange point in California.
  
  
• Client
  A client is a computer system that uses resources provided by another machine on the network. Most of NETMANAGE's applications can run as both client and server.
  
  
• Client-Server Model
  A common way to describe network services and the model user processes (programs) of those services. Examples include the name-server/name-resolver paradigm of the DNS and file-server/file-client relationships such as NFS and diskless hosts.
  
  
• CNAME - Canonical Name
  A domain name resource record used to specify an alias or alternate name to be associated with a particular IP address.
  
  
• CO - Central Office
  The Telco facility to which your local telephone circuit leads. Contains "Switches" and "Trunks" as well as the local telephone circuits.
  
  
• Command Line
  The entire command string, including the command and any parameters or qualifiers that it may have. A command is an instruction or request for the system to perform a particular action.
  
  
• config.sys file
  This file resides on all PCs, and it defines which device drivers ti install.
  
  
• CPE - Customer Premises Equipment
  Customer owned equipment located at their facility.
  
  
• CRC - Cyclic Redundancy Check
  A computational means to ensure the accuracy of frames transmitted between devices in a Frame Relay network. The mathematical function is computed, before the frame is transmitted, at the originating device. Its numerical value is computed based on the content of the frame. This value is compared with a re-computed value of the function at the destination device. See also Frame Check Sequence (FCS).
  
  
• CSD - Circuit Switched Data
  A dial-up data communications channel which, once established, looks like a transparent data pipe. Also, the type of ISDN service required to utilize this capability of an ISDN circuit. In contrast to CSV.
  
  
• CSU - Channel Service Unit
  A digital interface device that connects end-user equipment to the local digital telephone loop.
  
  
• CSV - Circuit Switched Voice
  A dial-up communications circuit for voice grade communication. Also, the type of ISDN service required to use this capability of an ISDN circuit. In contrast to CSD.
  
  
• Cyberspace
  A term coined by William Gibson in his fantasy novel Neuromancer to describe the "world" of computers and the society that gathers around them.
  
  
  D
  
  
• DCE - Data Communications Equipment
  When using serial communications such RS-232, V.35, or X.21, the DCE is the device sending/receiving from the Telco line, e.g. a modem or CSU/DSU. In contrast to DTE.
  
  
• D Channel - Data Channel
  Used when refering to ISDN lines. The ISDN BRI (Basic Rate Interface) has 2 64K B-channels and one D-channel. The B-channels are used for voice,data or video transmissions, while the D-channel is used for signaling.
  
  
• DDS - Digital Data System or Dedicated Digital Service
  A "Hardwired" or "Nailed Up" digital circuit which is permanently connected between 2 points. Typically 56Kbps or 64Kbps. Dedicated digital lines are frequently cheaper than ISDN for full time service.
  
  
• DE - Discard Eligibility
  A user-set bit indicating that a frame may be discarded in preference to other frames if congestion occurs, to maintain the committed quality of service within the network. Frames with the DE bit set are considered to be excess data.
  
  
• Demarc
  The "demarcation point," or the point where the telephone company's wiring stops and your wiring begins. In other words, the phone company will charge you extra for any wiring work performed on your side of the demarc.
  
  
• Dialup
  A temporary, as opposed to dedicated, connection between machines established over a standard phone line. As an Remote Access user you will dialup a POP (point-of-presence) for your connection to the Internet.
  
  
• Directory Number
  Your seven digit telephone number (without the area code), as found in the telephone directory.
  
  
• DLCI - Data Link Connection Identifier
  A unique number assigned to a PVC end point in a Frame Relay network. Identifies a particular PVC endpoint within a user's access channel in a Frame Relay network and has local significance only to that channel.
  
  
• Domain
  In the Internet, a part of a naming hierarchy. Syntactically, an Internet domain name consists of a sequence of names (labels) separated by periods (dots), e.g., "tundra.mpk.ca.us."
  
  
• DNS - Domain Name Service
  Distributed Internet service that maintains the relationship between domain names and IP addresses. DNS includes IP addresses, mail exchangers, aliases (CNAMEs) and other useful information. Some important domains are: .COM (commercial), .EDU (educational), .NET (network operations), .GOV (U.S. government), and .MIL (U.S. military).
  
  
• Download
  To transfer data or (especially) code from a larger host system (e.g. a mainframe) over a digital comm link to a smaller client system, especially a microcomputer or specialized peripheral.
  
  
• DSL - Digital Subscriber Line
  Typically refers to an ISDN line.
  
  
• DSU - Data Service Unit
  A device used in digital transmission for connecting data terminal equipment (DTE), such as a router, to a digital transmission circuit (DTC) or service.
  
  
• DTE - Data Terminal Equipment
  When using serial communications such RS-232, V.35, or X.21, the DTE is the device sending/receiving from a modem or CSU/DSU. In contrast to DCE.
  
  
• DTR - Data Terminal Ready
  A modem interface control signal sent from the DTE to the modem, usually telling the modem that the DTE is ready to transmit data.
  
  
• Dynamic Address Resolution
  Use of an address resolution protocol to determine and store address information on demand.
  
  
• Dynamic Routing
  Routing that adjusts automatically to network topology or traffic changes.
  
  
  E
  
  
• E1
  Transmission rate of 2.048 Mbps on E1 communications lines. An E1 facility carriers a 2.048 Mbps digital signal.
  
  
• Electronic Mail - E-Mail
  A system whereby a computer user can exchange messages with other computer users (or groups of users) via a communications network. Electronic mail is one of the most popular uses of the Internet.
  
  
• Email Address
  The UUCP or domain-based address associated with a user.
  
  
• Encapsulation
  The technique used by layered protocols in which a layer adds header information to the protocol data unit (PDU) from the layer above. As an example, in Internet terminology, a packet would contain a header from the physical layer, followed by a header from the network layer (IP), followed by a header from the transport layer (TCP), followed by the application protocol data.
  
  
• Encryption
  The manipulation of a packet's data in order to prevent anyone except the intended recipient from reading that data. There are many types of data encryption, and they are the basis of network security.
  
  
• End Device
  The ultimate source or destination of data flowing through a Frame Relay network is sometimes referred to as Data Terminal Equipment (DTE). As a source device, it sends data to an interface device for encapsulation in a Frame Relay frame. As a destination device, it receives de-encapsulated data (i.e., the Frame Relay frame is stripped off, leaving only the user's data) from the interface device. NOTE: An end device can be an application program or some operator-controlled device (e.g., workstation). In a LAN environment, the end device could be a file server or host.
  
  
• Ethernet
  A 10-Mb/s standard for LANs, initially developed by Xerox, and later refined by Digital, Intel and Xerox (DIX). All hosts are connected to a coaxial cable where they contend for network access using a Carrier Sense Multiple Access with Collision Detection (CSMA/CD) paradigm.
  
  
• ETSI - European Telecommunications Standards Institute
  Organization created by European PTTs and the EC (European Community) to propose telecommunications standards for Europe.
  
  
• Eudora
  An electronic mail program for the Macintosh and MS-Windows that is produced and distributed by Qualcomm. This program makes it possible for anyone with a POP account and a Macintosh or MS-Windows connected to the network to use their workstation to read, compose, and send mail. In addition to text messages, Eudora allows you to receive binary files, such as formatted documents, that have been sent by other people who are using Eudora or other mail readers.
  
  
• Exchange
  Another name for a Central Office (CO).
  
  
  F
  
  
• FAX - Facsimile
  Long distance copy; the transfer of graphical data between two fax units. The graphical data is compressed during transfer.
  
  
• File Server
  A process running on a computer that provides access to files on that computer, to programs running on remote machines. File access, the FTP protocol, and the file servers, are what make "FTP'ing" successful.
  
  
• File Transfer
  The copying of a file from one computer to another over a computer network.
  
  
• Filter
  Generally, a process or device that screens incoming information for certain characteristics, allowing a subset of that information to pass through.
  
  
• Finger
  A program that displays information about a particular user, or all users, logged on the local system or on a remote system. It typically shows full name, last login time, idle time, terminal line, and terminal location (where applicable). It may also display plan and project files left by the user.
  
  
• Firewalls
  Firewalls are designed specifically to control unwarranted access to your network, and usually embrace a much more conservative security philosophy: "That which is not expressly permitted is denied." They can also deal with some of the trickier protocols. Besides providing stronger logging capabilities, many firewalls can provide features like network address translation, authentication and virtual private networks.
  
  
• Firmware
  Software instructions set permanently or semi-permanently in ROM.
  
  
• Flame
  To express strong opinion and/or criticism of something, usually as a frank inflammatory statement in an E-mail message. More often found in USENET news groups.
  
  
• Flooding
  Routing technique by which routing information received by a routing device is sent out each of that device's interfaces except (usually) the interface on which the information was received.
  
  
• Flow Control
  A technique for ensuring that a transmitting entity does not overwhelm a receiving entity. In IBM networks, this technique is called pacing.
  
  
• Forwarding
  The process of sending a frame toward its ultimate destination by an internet-working device.
  
  
• FQDN - Fully Qualified Domain Name
  The FQDN is the full name of a system, rather than just its hostname. For example, "venera" is a hostname and "venera.isi.edu" is an FQDN. See also: hostname, Domain Name System.
  
  
• FR - Frame Relay
  A telephony technology implemented by PSINet that allows for more robust and dynamic routing.
  
  
• Fractional T1
  A service provided by North American carriers where a full T1 link is given to the customer, but the service charge is calculated based on the number of timeslots used.
  
  
• Frame Relay Frame
  A variable-length unit of data, in Frame Relay format, that is transmitted through a Frame Relay network as pure data.
  
  
• Frame Relay Network
  A telecommunications network based on Frame Relay technology. Data is multiplexed.
  
  
• Frequency
  Measured in Hertz (Hz), the number of cycles of an alternating current signal per unit time.
  
  
• FTP - File Transfer Protocol
  A protocol which allows a user on one host to access and transfer files to and from another host over a network. Also, FTP is usually the name of the program the user invokes to execute the protocol. It is defined in STD 9, RFC959.
  
  
• Full Pathname
  The name of a directory or file in relation to the root (/) directory.
  
  
• FYI (For Your Information)
  A subseries of RFCs that are not technical standards of descriptions of protocols. FYIs convey general information about topics related to TCP/IP or the Internet. See also: Request For Comments, STD.
  
  
  G
  
  
• Gateway
  The term "router" is now used in place of the original definition of "gateway." Currently, a gateway is a communications device/program which passes data between networks having similar functions but dissimilar implementations.
  
  
• Gopher
  A distributed information service that makes available hierarchical collections of information across the Internet. Gopher uses a simple protocol that allows a single Gopher client to access information from any accessible Gopher server, providing the user with a single "Gopher space" of information.
  
  
• Group ID
  A unique number associated with each group name on the server.
  
  
• GUI - Graphical User Interface
  Refers to the techniques involved in using graphics, along with a keyboard and a mouse, to provide an easy to use interface to some program.
  
  
  H
  
  
• Hacker
  A person who delights in having an intimate understanding of the internal workings of a system, computers and computer networks in particular. The term is often misused in a pejorative context, where "cracker" would be the correct term.
  
  
• Handshake
  Sequence of messages exchanged between two or more network devices to ensure transmission synchronization.
  
  
• Handshaking
  Exchange of predetermined signals between two devices establishing a connections protocol.
  
  
• H Channel
  Similar to a B-Channel, but 384k instead of 64k. Found on PRIs.
  
  
• HDLC - High Level Data Link Control
  A generic link-level communications protocol developed by the International Organization for Standardization (ISO). HDLC manages synchronous, code-transparent, serial information transfer over a link connection.
  
  
• HDSL - High Level Digital Subscribe Line
  Modems on either end of one or more twisted pair wires that deliver T1 or E1 speeds. At present T1 requires two lines and E1 requires three.
  
  
• Header
  The portion of a packet, preceding the actual data, containing source and destination addresses, and error checking and other fields. A header is also the part of an electronic mail message that precedes the body of a message and contains, among other things, the message originator, date and time.
  
  
• Highspeed Modem
  A modem that works at bit rates higher than 9600 bps.
  
  
• Holddown
  A state into which a route can be placed whereby routers will neither advertise the route nor believe advertisements about the route for a specific length of time (the holddown period) in order to flush bad information about that route from all routers in the network. A route can be placed in holddown when a link in that route fails.
  
  
• Home Directory
  In UNIX, the directory in which you are placed immediately after you login.
  
  
• Home Page
  The document initially displayed when starting up a web browser.
  
  
• Hop
  A single trunk line between two switches in a Frame Relay network. An established PVC consists of a certain number of hops, spanning the distance from the ingress access interface to the egress access interface within the network.
  
  
• Hop Count
  A routing metric used to measure the distance between a source and a destination.
  
  
• Host
  A computer that allows users to communicate with other host computers on a network. Individual users communicate by using application programs, such as Electronic Mail, Telnet and FTP.
  
  
• Host Address
  The IP address given to a machine.
  
  
• Host Name
  The name given to a machine.
  
  
• Host Table
  An ASCII text file where each line is an entry consisting of one numeric address and one or more names associated with that address. This allows an Remote Access user, for example, to send mail to a group of people or addresses via one address.
  
  
• HSSI - High-Speed Serial Interface
  Network standard for high-speed (up to 52 Mbps) serial communications over WAN links.
  
  
• HTML - HyperText Markup Language
  The coding language used to create Hypertext documents for use on the World Wide Web. HTML looks a lot like old-fashioned typesetting code, where a block of text is surrounded by codes that indicate how the text should appear. Also, in HTML you can specify that a block of text, or a word, is "linked" to another file on the Internet. HTML files are meant to be viewed using a World Wide Web Client program, such as Mosaic, Netscape, etc.
  
  
• .HTML
  The extension used on a file that is coded using HTML.
  
  
• HTTP - HyperText Transport Protocol
  The protocol (RFC 1945) for moving hypertext files across the Internet. Requires an HTTP client program on one end, and an HTTP server program on the other end. HTTP is the most important protocol used in the World Wide Web (WWW).
  
  
• Hub
  A device connected to several other devices. In ARCnet, a hub is used to connect several computers together. In a message handling service, a hub is used for the transfer of messages across the network. In Ethernet / IEEE 802.3 terminology, a hub is an Ethernet multiport repeater, which is sometimes referred to as a concentrator. The term is also used to refer to a hardware/software device that contains multiple independent but connected modules of network and internetwork equipment. Hubs can be active (where they repeat signals sent through them) or passive (where they do not repeat, but merely split, signals sent through them).
  
  
• Hyperlink
  A "hotspot" that links one document to another. In Mosaic and Netscape, a hyperlink is displayed as a highlighted word or graphic (color and/or underlining). Clicking on a hyperlink takes to you to the linked document.
  
  
• Hypertext
  Generally, any text that contains "links" to other documents - words or phrases in the document that can be chosen by a reader and which cause another document to be retrieved and displayed.
  
  
  I
  
  
• IBGP - Internal Border Gateway Protocol
  A variation of BGP that is used internal to a single Autonomous System.
  
  
• ICMP - Internet Control Message Protocol
  IP protocol used to indicate problems on the network, such as network unreachable and time-to-live exceeded.
  
  
• IDN - Integrated Digital Network
  The telephone network using digital switching.
  
  
• IEC - InterExchange Carrier
  "Long Distance" carrier. Handles Interlata and interstate calls.
  
  
• IGRP - Inter-Gateway Routing Protocol
  Cisco Systems proprietary distance-vector routing protocol, used within a single Autonomous system.
  
  
• Ingress
  Frame Relay frames from an access device toward the Frame Relay network.
  
  
• Interface Device
  Provides the interface between the end device(s) and a Frame Relay network by encapsulating the user's native protocol in Frame Relay frames and sending the frames across the Frame Relay backbone.
  
  
• Internet
  A collection of networks interconnected by a set of routers which allow them to function as a single, large virtual network.
  
  
• (The) Internet
  The largest internet in the world consisting of large national backbone nets (such as MILNET, NSFNET, and CREN) and a myriad of regional and local campus networks all over the world. The Internet uses the Internet protocol suite. To be on the Internet you must have IP connectivity, i.e., be able to Telnet to--or ping--other systems. Networks with only e-mail connectivity are not actually classified as being on the Internet.
  
  
• IP - Internet Protocol
  A layer 3 (network layer) protocol that contains addressing information and some control information that allows packets to be routed (RFC 791).
  
  
• IP Address
  The 32-bit address defined by the Internet Protocol in STD 5, RFC 791. It is usually represented in dotted decimal notation.
  
  
• IP Datagram
  The fundamental unit of information passed across the Internet. Contains source and destination addresses along with data and a number of fields which define such things as the length of the datagram, the header checksum, and flags to say whether the datagram can be (or has been) fragmented.
  
  
• IPX -Internetwork Packet eXchange
  Novell's protocol used by Netware. A router with IPX routing can interconnect LANs so that Novell Netware clients and servers can communicate.
  
  
• ISDN - Integrated Services Digital Network
  Communication protocols proposed by telephone companies to permit telephone networks to carry data, voice, and other source material.
  
  
• ISO - International Standards Organization
  A voluntary, nontreaty organization founded in 1946 which is responsible for creating international standards in many areas, including computers and communications. Its members are the national standards organizations of the 89 member countries, including ANSI for the U.S.
  
  
• ISP - Internet Service Provider
  A company that provides access to the Internet to other parties.
  
  
• ITU - International Telecommunications Union
  United Nations organization with representatives from the PTTs of the world. The ITU, headquartered in Geneva, Switzerland is an international organization within which governments and the private sector coordinate global telecom networks and services. ITU activities include the coordination, development, regulation and standardization of telecommunications and organization of regional and world TELECOM events.
  
  
• IXC - IntereXchange Carrier
  See IEC.
  
  
  K
  
  
• KBPS - Kilobits Per Second
  Kbps refers to the rate of data transfer. The highest rate of transfer possible on an analog modem connection is theoretically 56 Kbps, while digital connections are not as limited. Using BRI ISDN, for example, transfer rates in the range of 115 to 128 Kbps are standard.
  
  
• Kermit
  A popular file transfer protocol developed by Columbia University. Because Kermit runs in most operating environments, it provides an easy method of file transfer. Kermit is NOT the same as FTP.
  
  
• Kernel
  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 kernel 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.
  
  
• Kilobyte
  A thousand bytes: actually, usually 1024 (2^10) bytes.
  
  
  L
  
  
• LAN - Local Area Network
  A privately owned network that offers high-speed communications channels to connect information processing equipment in a limited geographic area.
  
  
• LAPD - Link Access Protocol D
  A protocol that operates at the data link layer (layer 2) of the OSI architecture. LAPD is used to convey information between layer 3 entities across the frame relay network. The D-channel carries signaling information for circuit switching.
  
  
• LATA - Local Access and Transport Area
  The area within which calls are routed by your Local Exchange Carrier (LEC). Calls going outside this area must be handled by an Interexchange carrier (IEC).
  
  
• Latency
  The amount of time between when a device requests access to a network and when it is granted permission to transmit.
  
  
• Layer
  Communication networks for computers may be organized as a set of more or less independent protocols, each in a different layer (also called level). The lowest layer governs direct host-to-host communication between the hardware at different hosts; the highest consists of user applications. Each layer builds on the layer beneath it. For each layer, programs at different hosts use protocols appropriate to the layer to communicate with each other. TCP/IP has five layers of protocols; OSI has seven. The advantages of different layers of protocols is that the methods of passing information from one layer to another are specified clearly as part of the protocol suite, and changes within a protocol layer are prevented from affecting the other layers. This greatly simplifies the task of designing and maintaining communication programs.
  
  
• LCP - Link Control Protocol
  The LCP is used to automatically agree upon the encapsulation format options, handle varying limits on sizes of packets, authenticate the identity of its peer on the link, determine when a link is functioning properly and when it is defunct, detect a looped-back link and other common misconfiguration errors, and terminate the link.
  
  
• Leased Line
  A telephone line reserved for the exclusive use of a customer, without interchange switching arrangements.
  
  
• LEC - Local Exchange Carrier
  Your local telephone service provider. In contrast to IEC.
  
  
• Line Card
  The circuit in the Telco switch to which your line is connected. On an ISDN circuit, the line card performs a role analogous to the NT-1 at the customer premises.
  
  
• Link
  In data communication, a connection between two pieces of equipment. Also referred to as point-to-point. Network communications channel consisting of a circuit or transmission path, including all equipment, between a sender and a receiver. Most often used to refer to a WAN connection. Sometimes referred to as a line.
  
  
• LMI - Local Management Interface
  For Frame Relay. Packet containing sequence-number exchange between a DTI (router) and a switch. It is used by the switch to learn which DLCIs are defined and the current status of the DLCIs.
  
  
• Load Balancing
  In routing, the ability of a router to distribute traffic over all its network ports that are the same distance from the destination address. Good load-balancing algorithms use both line speed and reliability information. Load balancing increases the utilization of network segments, thus increasing effective network bandwidth.
  
  
• Local Bridge
  A bridge that directly interconnects networks in the same geographic area.
  
  
• Local Host
  In UNIX, the host on the network you are currently using.
  
  
• Local Loop
  The line from a telephone subscriber's premises to the telephone company CO.
  
  
• Log In
  To perform a sequence of actions at a terminal that establishes a user's valid connection to a service. In Remote Access Service, your "login" is actually your username account number (ppxxxxxx).
  
  
• Loop
  The telephone circuit from the CO to the customer's premises. Generally refers to a copper cable circuit.
  
  
• Loopback
  A type of diagnostic test in which the transmitted signals are returned to the sending device after passing through all or part of a communications link or network. A loopback test permits the comparison of a returned signal with the transmitted signal.
  
  
• Loop Qualification
  Process of actually measuring the loss on an prospective ISDN line to see if it can be used for ISDN service. The actual loss on the line is the determining factor whether ISDN service can be offered without a repeater. Generally ISDN is available up to 18,000 feet from the serving CO. It may not be available within this range, or may be available further from the CO. Only a loop qualification can tell for sure. Not all Telcos will extend ISDN lines with repeaters.
  
  
  M
  
  
• Mail Exploder
  Part of an electronic mail delivery system which allows a message to be delivered to a list of addressees. Mail exploders are used to implement mailing lists. Users send messages to a single address (e.g., hacks@somehost.edu) and the mail exploder takes care of delivery to the individual mailboxes in the list. WARNING: Mail exploding is extremely hard to trace, extremely hard to stop, and can result in a mail bombing effect to the user.
  
  
• Mail Gateway
  A machine that connects two or more electronic mail systems (especially dissimilar mail systems on two different networks) and transfers messages between them. Sometimes the mapping and translation can be quite complex, and generally it requires a store-and-forward scheme whereby the message is received from one system completely before it is transmitted to the next system after suitable translations.
  
  
• Mail Server
  A software program that distributes files or information in response to requests sent via email.
  
  
• Mailing List
  A possibly moderated discussion group, distributed via email from a central computer maintaining the list of people involved in the discussion.
  
  
• MAN - Metropolitan Area Network
  A data network intended to serve an area approximating that of a large city. Such networks are being implemented by innovative techniques, such as running fiber cables through subway tunnels. A popular example of a MAN is SMDS.
  
  
• Martian
  Humorous term applied to packets that turn up unexpectedly on the wrong network because of bogus routing entries. Also used as a name for a packet which has an altogether bogus (non-registered or ill-formed) Internet address.
  
  
• Megabyte
  A million bytes. A thousand kilobytes.
  
  
• Megalink
  Bell Canada’s trademarked name for the line required for PRI ISDN.
  
  
• Microlink
  Bell Canada’s trademarked name for the line required for BRI ISDN.
  
  
• Microwave
  Electromagnetic waves in the range of 1 to 30 gigahertz. Microwave-based networks are a nascent technology gaining favor due to high bandwidth and relatively low cost.
  
  
• MIME - Multipurpose Internet Mail Extensions
  An extension to Internet email which provides the ability to transfer non-textual data, such as graphics, audio, video and fax.
  
  
• Modem - Modulator-Demodulator
  A device used to convert serial digital data from a transmitting DTE to a signal suitable for transmission over telephone lines. It also reconverts the transmitted signal to serial digital data for acceptance by a receiving DTE.
  
  
• MPP - Multi-link PPP
  Allows you to combine two or more B Channels into a single, faster PPP connection. With Multi-link PPP, you could have a 128 kilobit/second PPP connection over a Basic Rate ISDN line.
  
  
• MTA - Mail Transport Agent
  The program that is responsible for the delivery of a message from one host to another.
  
  
• MTU - Maximum Transmission Unit
  The largest frame length which may be sent on a physical medium.
  
  
• MUA - Mail User Agent
  The program that is used to create, read and manage electronic mail messages.
  
  
• Multiplexing
  Putting multiple signals on a single channel.
  
  
• Multitasking
  The execution of two or more processes at the same time.
  
  
• MX - Mail Exchanger
  Domain Name resource record used to direct the delivery of mail to the desired mail server(s).
  
  
• MX Record - Mail eXchange Record
  A DNS resource record type indicating which host can handle mail for a particular domain.
  
  
  N
• Nagware
  The variety of shareware that displays a large screen at the beginning or end reminding you to register, typically requiring some sort of keystroke to continue so that you can't use the software in batch mode.
  
  
• Name Caching
  Method by which remotely discovered host names are stored by a router for use in future packet-forwarding decisions for quick access.
  
  
• Name Resolution
  The process of mapping a name into the corresponding address. For example, if you are trying to ping a host, if you type in an IP (Internet Protocol) address, the DNS will return a name in the bottom left corner of the ping box. If you type in a host name, the DNS will return an IP address. See DNS.
  
  
• Name Server
  A server provided on the network that resolves network names into network locations (addresses).
  
  
• Nastygram
  A protocol packet or item of email (the latter is also called a letterbomb) that takes advantage of misfeatures or security holes on the target system to do untoward things.
  
  
• National ISDN
  The first US "standardized" multi-platform ISDN protocol. The first version is National ISDN-1. As of mid 1996, National ISDN-2 was implemented in some areas and is fully backward compatible with National ISDN-1. Future versions of National ISDN will be named using the year of release (e.g. National ISDN-97).
  
  
• NDIS - Network Device Interface Specification
  The NDIS specification is used for all communication with network adapters. The specification was developed by Microsoft and 3COM to provide a common programming interface for MAC drivers and transport drivers. NDIS works primarily with LAN manager and allows multiple protocol stacks to share a single network interface card.
  
  
• NetBEUI - NetBios Extended User Interface
  Pronounced "net-booey," this is an enhanced version of the Netbios protocol used by network operating systems such as LAN Manager, LAN Server, Windows for Workgroups, Windows 95 and Windows NT. It formalizes the transport frame that was never standardized in Netbios and adds additional functions. The transport layer driver frequently used by Microsoft's LAN Manager, Windows for Workgroups, and Windows NT. Netbeui implements the OSI LLC2 protocol.
  
  
• NetBIOS - Network Basic Input/Output System
  The standard interface to networks on systems using DOS, OS/2, and some versions of UNIX that provides standard ways for applications to interact with a LAN (e.g. request lower-level network services).
  
  
• Netscape
  A World Wide Web client developed by Netscape Communications Corporation.
  
  
• NetWare
  Developed and marketed by Novell, Inc., the world's most popular distributed filer system. NetWare provides transparent remote file access and numerous other distributed network services.
  
  
• Network
  A computer network is a data communications system which interconnects computer systems at various different sites. A network may be composed of any combination of LANs, MANs or WANs. NOTE: The Network is the union of all the major noncommercial, academic, and hacker-oriented networks, such as the Internet, the old ARPANET, NSFnet, BITNET, and the virtual UUCP and USENET 'networks,' plus the corporate in-house networks and commercial time-sharing services (such as CompuServe) that gateway to them. A site is generally considered 'on the network' if it can be reached through some combination of Internet-style (@-sign) and UUCP (bang-path) addresses.
  
  
• Network Address
  The network portion of an IP address. For a class A network, the network address is the first byte of the IP address. For a class B network, the network address is the first two bytes of the IP address. For a class C network, the network address is the first three bytes of the IP address. In each case, the remainder is the host address. In the Internet, assigned network addresses are globally unique.
  
  
• Network Administrator
  Person who helps maintain a network.
  
  
• Network Analyzer
  A hardware/software device offering various network trubleshooting features, including protocol-specific packet decodes, specific programmed troubleshooting tests, packet filtering, and packet transmission.
  
  
• Network Interface
  The boundary between a carrier's network and a local installation.
  
  
• Network Layer
  Layer 3 of the OSI reference model. Layer 3 is the layer at which routing occurs.
  
  
• Network Number
  See network address.
  
  
• Network Printing
  Printing to a shared printer locally attached to one of the PCs on the network.
  
  
• Newbie
  A USENET neophyte. This term surfaced in the {newsgroup} talk.bizarre but is now in wide use. Criteria for being considered a newbie vary wildly; a person can be called a newbie in one newsgroup while remaining a respected regular in another. The label `newbie' is sometimes applied as a serious insult to a person who has been around USENET for a long time but who carefully hides all evidence of having a clue.
  
  
• Newsgroup
  (USENET) Usenet groups can be 'unmoderated' (anyone can post) or 'moderated' (submissions are automatically directed to a moderator, who edits or filters and then posts the results).
  
  
• NEWT
  NEWT is a TCP/IP communication stack for Microsoft Windows. NEWT provides users a degree of network access previously only available to workstations and mainframe users. Commonly, the Remote Access Support Group will request users to click the green NEWT icon that appears when running the Custom application. This NEWT provides various needed information about a users connection.
  
  
• NFAS - Non-Facility Associated Signaling
  NFAS enables multiple PRI lines to be supported by a single 64 Kbps D channel.
  
  
• NFS
  Network File System. A protocol developed by SUN Microsystems that uses IP to allow a set of computers to access each others file systems as if they were local. Originally designed for UNIX systems, this protocol has been implemented on many other operating systems, including DOS and Windows.
  
  
• NIC - Network Information Center
  A NIC provides information, assistance and services to network users. Originally there was only one, located at SRI International and tasked to serve the ARPANET (and later DDN) community. Today, there are many NICs, operated by local, regional, and national networks all over the world.
  
  
• NIU - Network Interface Unit
  A physical network adapter (for example, an Ethernet card).
  
  
• NNTP - Network News Transport Protocol
  The Internet protocol that defines the transmission and operations of Network News.
  
  
• NOC
  Network Operations Center. Any center tasked with the operational aspects of a production network. These tasks include monitoring and control, trouble-shooting, user assistance, and so on. Remote Access customers are not able to e-mail operations directly.
  
  
• Node
  An addressable device attached to a computer network. See also host, router. In data communication, a point of interconnection to a network.
  
  
• NS - Nanosecond
  One-billionth of a second.
  
  
• NS - Name Server
  A domain name resource record used to indicate the authoritative name servers for a given zone.
  
  
• NSAP - Network Service Access Point
  The point at which the OSI Network Service is made available to a Transport entity. The NSAPs are identified by OSI Network Addresses as specified by ISO 8348/Ad2. The point at which OSI Network Service is made available to a layer 4 entity.
  
  
• NSF
  National Science Foundation. Sponsors of the NSFNET.
  
  
• NSFNET
  National Science Foundation NETwork. A collection of local, regional, and mid-level networks in the U.S. tied together by a high-speed backbone. NSFNET provides scientists access to a number of supercomputers across the country.
  
  
• NT-1 - Network Termination 1
  NT-1 is the device which converts the two-wire U Interface into the four-wire or eight-wire S/T Interface. This enables standard ISDN terminal equipment to plug into a standard eight-pin RJ-45 connector. Some terminal adapters have the NT-1 built into them for an easier installation.
  
  
• NT-2 - Network Termination 2
  NT-2 is the device which converts the T Interface into the S Interface.
  
  
• Nuke
  To intentionally delete the entire contents of a given directory or storage volume. "On UNIX, `rm -r /usr' will nuke everything in the usr filesystem."
  
  
• Null Modem
  Small box or cable used to join computing devices directly, rather than over a network.
  
  
  O
  
  
• Octet
  An octet is 8 bits. This term is used in networking, rather than byte, because some systems have bytes that are not 8 bits long.
  
  
• Offline
  Not now or not here. "Let's take this discussion offline." Specifically used on USENET to suggest that a discussion be moved off a public newsgroup to email. Offline can also refer to a user who is not physically connected to a service.
  
  
• ONC(tm) - Open Network Computing
  A distributed applications architecture promoted and controlled by a consortium led by Sun Microsystems.
  
  
• Operating System
  (Often abbreviated 'OS'.) The foundation software of a machine, of course; that which schedules tasks, allocates storage, and presents a default interface to the user between applications. The facilities an operating system provides and its general design philosophy exert an extremely strong influence on programming style and on the technical cultures that grow up around its host machines.
  
  
• OSI - Open Systems Interconnect
  A suite of protocols, designed by ISO committees, to be the international standard computer network architecture.
  
  
• OSI Network Address
  The address, consisting of up to 20 octets, used to locate an OSI Transport entity. The address is formatted into an Initial Domain Part which is standardized for each of several addressing domains, and a Domain Specific Part which is the responsibility of the addressing authority for that domain.
  
  
• OSI Presentation Address
  The address used to locate an OSI Application entity. It consists of an OSI Network Address and up to three selectors, one each for use by the Transport, Session, and Presentation entities.
  
  
• OSI Reference Model
  A network architectural model developed by ISO and CCITT. The model consists of seven layers, each of which specifies particular network functions such as addressing, flow control, error control, encapsulation, and reliable message transfer. The highest layer (the application layer) is closest to the media technology. The OSI reference model is used universally as a method for teaching and understanding network functionality.
  
  
  P
  
  
• Packet
  A group of fixed-length binary digits, including the data and call control signals, that are transmitted through an X.25 packet-switching network as a composite whole. The data, call control signals, and possible error control information are arranged in a predetermined format. Packets do not always travel the same pathway but are arranged in proper sequence at the destination side before forwarding the complete message to an addressee.
  
  
• Packet Switched Data
  Packet switched data is data that is broken down into standard sized packets then sent through the network. The packets each carry the destination address and the information required to reassemble them when they reach their destination.
  
  
• Patch
  A temporary addition to a piece of code, usually as a "quick-and-dirty" remedy to an existing bug or misfeature. A patch may or may not work, and may or may not eventually be incorporated permanently into the program.
  
  
• Path
  A bang path or explicitly routed Internet address; a node-by-node specification of a link between two machines. UNIX: A filename, fully specified relative to the root directory (as opposed to relative to the current directory; the latter is sometimes called a `relative path'). This is also called a 'pathname'.
  
  
• PBX - Private Branch Exchange
  A privately owned switch. Basically a PBX is a private "business" telephone system which also interfaces to the telephone network. Many PBX's can now offer ISDN BRI service, usually over the S Interface. A few vendors are now offering BRI over the U interface as well. Be wary of these ISDN protocols since they have not been as well tested. They may or may not work with a given piece of CPE.
  
  
• PCI
  Protocol Control Information. The protocol information added by an OSI entity to the service data unit passed down from the layer above, all together forming a Protocol Data Unit (PDU).
  
  
• PD
  Common abbreviation for `public domain', applied to software distributed over {USENET} and from Internet archive sites. Much of this software is not in fact public domain in the legal sense but travels under various copyrights granting reproduction and use rights to anyone who can snarf a copy. This Public Domain software is often unsupported by vendors and service providers, due to the large numbers of PD files.
  
  
• PDU
  Protocol Data Unit. This is OSI terminology for "packet." A PDU is a data object exchanged by protocol machines (entities) within a given layer. PDUs consist of both Protocol Control Information (PCI) and user data.
  
  
• Physical Layer
  The OSI layer that provides the means to activate and use physical connections for bit transmission. In plain terms, the Physical Layer provides the procedures for transferring a single bit across a Physical Media.
  
  
• Physical Media
  Any means in the physical world for transferring signals between OSI systems. Considered to be outside the OSI Model, and therefore sometimes referred to as "Layer 0." The physical connector to the media can be considered as defining the bottom interface of the Physical Layer.
  
  
• PING - Packet Internet Groper
  Internet application that allows you to verify IP connectivity to a particular host. Used to test reachability of destinations by sending them an ICMP echo request and waiting for a reply. The term is used as a verb: "Ping host X to see if it is up!" It reports success or failure and statistics about an operation.
  
  
• POP - Point of Presence
  Location of equipment that allows customers to connect to the Internet. The local facility where your IEC maintains a switch. This is where your long distance calls get sent so that your IEC can handle them.
  
  
• POP - Post Office Protocol
  Client/server application used to send and receive e-mail.
  
  
• Port
  The abstraction used by Internet transport protocols to distinguish among multiple simultaneous connections to a single destination host.
  
  
• Posting
  Distinguished from a `letter' or ordinary email message by the fact that it is broadcast rather than point-to-point. Remote Access users have the access to post to any subscribed newsgroup of there choice, where their posting can be viewed by anyone subscribed to the group.
  
  
• Postmaster
  The person responsible for taking care of electronic mail problems, answering queries about users, and other related work at a site.
  
  
• POTS - Plain Old Telephone Service
  An analog (non-digital) telephone line.
  
  
• Power Cycle
  To power off a machine and then power it on immediately, with the intention of clearing some kind of hung or gronked state.
  
  
• PPP - Point to Point Protocol
  The Point-to-Point Protocol, defined in RFC 1661, provides a standard method for transporting multi-protocol datagrams over point-to-point links.
  
  
• Presentation Layer
  The OSI layer that determines how Application information is represented (i.e., encoded) while in transit between two end systems.
  
  
• PRI - Primary Rate Interface
  PRI ISDN service consists of 23 B channels and one D channel. All channels are 64 Kbps. PRI is typically only required by ISPs or other telecommunications organizations providing third party dialup access.
  
  
• Prompt
  Word or words used by the system to assist a user's response. Such messages generally ask the user to respond by typing some information in a certain field.
  
  
• Propagation Delay
  The time required for data to travel over a network from source to ultimate destination.
  
  
• Protocol
  A formal description of message formats and the rules two computers must follow to exchange those messages. Protocols can describe low-level details of machine-to-machine interfaces (e.g., the order in which bits and bytes are sent across a wire) or high-level exchanges between allocation programs (e.g., the way in which two programs transfer a file across the Internet).
  
  
• Proxy
  The mechanism whereby one system "fronts for" another system in responding to protocol requests. Proxy systems are used in network management to avoid having to implement full protocol stacks in simple devices, such as modems.
  
  
• PSN - Packet Switch Node
  A dedicated computer whose purpose is to accept, route and forward packets in a packet switched network.
  
  
• PSTN - Public Switched Telephone Network
  Refers to the telephone network.
  
  
• PVC - Permanent Virtual Circuit
  A feature of Frame Relay that allows the configuration of virtual circuits across the Internet.
  
  
  Q
  
  
• Query
  Message used (usually in a request-response protocol) to inquire about the value of some variable or set of variables.
  
  
• Queue
  Generally, an ordered list of elements waiting to be processed. In routing, a backlog of packets waiting to be forwarded over a router interface.
  
  
• Queueing Delay
  The amount of time that data must wait before it can be transmitted onto a statistically multiplexed physical circuit.
  
  
  R
  
  
• Rate Adaptation
  Since many PCs have a maximum output of less than 64 Kbps, rate adaptation enables the terminal to adapt to a slower bit rate. For data transfer, the rate adaptation scheme must be the same for the sender and receiver. For ISDN, V120 is quickly becoming the standard for asynchronous rate adaptation.
  
  
• RBOC
  Regional Bell Operating Company. These are the companies that were formed following the Bell Telephone breakup (Baby Bell's). These are also the companies to contact regarding establishing an ISDN connection. This information is also available through Mosaic at http://www.bellcore.com/. Also see BOC.
  
  
• RD - Receive Data
  Data coming from the network, or DCE towards the DTE. Also, a light on a modem or CSU/DSU which lights to indicate presence of this signal.
  
  
• Redirect
  A part of the ICMP and ES-IS protocols that allows a router to tell a host that use of another router would be more effective.
  
  
• Redistribution
  Allowing routing information discovered through one routing protocol to be distributed in another routing protocol's update messages.
  
  
• Redundancy
  In telephony, the portion of the total information contained in a message that can be eliminated without loss of essential information or meaning. In computing, multiple (redundant) system elements that perform the same function.
  
  
• Remote
  Files, devices and users not attached to your local machine.
  
  
• Remote Host
  Another computer at another location that can be connected to via the Internet.
  
  
• Remote Printer
  A printer that can be used by your local computer that is not directly connected to the local computer, and must be accessed using a network connect.
  
  
• Repeater
  A physical device which propagates electrical signals from one cable to another. This is similar to repeaters that are used by most phone companies to pass on phone calls over very long distances. See bridge and router.
  
  
• Resources
  Used in the context of "internet resources" this refers to anything that can be used and controlled by a computer, or its user. This includes files, physical (and logical) devices, applications, processes, peripherals, etc...
  
  
• RFC - Request For Comment
  The document series, begun in 1969, which describes the Internet suite of protocols and related experiments. Not all (in fact very few) RFCs describe Internet standards, but all Internet standards are written up as RFCs. The RFC series of documents is unusual in that the proposed protocols are forwarded by the Internet research and development community, acting on their own behalf, as opposed to the formally reviewed and standardized protocols that are promoted by organizations such as CCITT and ANSI.
  
  
• RFC 822
  The internet standard format for electronic mail message headers. All e-mail has header information defining To, From, Subject, Time, Date, etc... This information is defined by this RFC.
  
  
• RIP - Routing Information Protocol
  Simple distance-vector routing protocol used within an Autonomous System.
  
  
• RJ-11
  The most common telephone jack in the world, this is a six-conductor modular jack wired with 4 wires.
  
  
• RJ-45
  An 8-pin connector jack used with standard telephone lines, and required by some ISDN hardware. A little larger than a RJ-11 jack.
  
  
• Root Directory
  In UNIX the directory located at the top of the UNIX file system. It is represented by the "/" (forward slash) character.
  
  
• Route
  The path that network traffic takes from its source to its destination. Also, a possible path from a given host to another host or destination.
  
  
• Router
  A device which routes network traffic from one interface to another. It does this at the software layer by routing either IP or other protocols.
  
  
• Routing Protocol
  A protocol that accomplishes routing through the implementation of a specific routing algorithm. Examples of routing protocols include IGRP, RIP, and OSPF.
  
  
• Routing Table
  A table stored in a router or some other internetworking device that keeps track of routes (and, in some cases, metrics associated with those routes) to particular network destinations.
  
  
• RR - Resource Records
  The Domain Name Service is made up of resource records - constructs that define the properties of fully qualified domain names.
  
  
  S
  
  
• SAP - Service Access Point
  The point at which the services of an OSI layer are made available to the next higher layer. The SAP is named according to the layer providing the services: e.g. transport services are provided at a Transport SAP (TSAP) at the top of the transport layer.
  
  
• Script
  A sequence of commands, usually stored as ASCII, that can be processed to automate various tasks.
  
  
• SDLC - Synchronous Data Link Control
  A link-level communications protocol used in an International Business Machines (IBM) Systems Network Architecture (SNA) network that manages synchronous, code-transparent, serial information transfer over a link connection. SDLC is a subset of the more generic High-Level Data Link Control (HDLC) protocol developed by the International Organization for Standardization (ISO).
  
  
• Server
  A provider of resources. These can be further defined according to what type of resource they offer. It is usually a computer that provides services to a network. Types of servers include Print Servers, Information Servers, and Web Servers.
  
  
• SGMP
  Simple Gateway Management Protocol. A simple set of rules that were originally used to manage InterNet traffic. These rules eventually evolved into it's predecessor SNMP, or Simple Network Management Protocol.
  
  
• Signaling
  Signaling is a term referring to the way that information pertaining to call set-up is passed from node to node in the phone system. The most commonly known form of signaling are the frequencies associated with touch tone. These frequencies are your POTS phone's way of signaling to the central office the information that the CO requires to process your call. With ISDN, all signaling is done on a separate data circuit (out of band), using a standard known as Signaling System 7.
  
  
• Signature
  The three or four lines at the end of a e-mail message that identifies the sending party. The Chameleon software allows Remote Access users to design their own signature file, by choosing "Settings", and then "Preferences" in the Mail application. There, you will find the Signature option.
  
  
• S-Interface
  BRI ISDN delivered over four wires. The maximum loop length for this interface is one kilometer.
  
  
• SLIP - Serial Line IP
  An Internet protocol used to run IP over serial lines such as telephone circuits or RS-232 cables interconnecting two systems. SLIP is now being replaced by PPP, which is used by Remote Access connections.
  
  
• SMDS - Switched Multimegabit Data Service
  An emerging high-speed datagram-based public data network service developed by Bellcore and expected to be widely used by telephone companies as the basis for their data networks.
  
  
• SMTP - Simple Mail Transfer Protocol
  Most common protocol used to transport e-mail across the Internet.
  
  
• Snail Mail
  A term used to describe the U.S. Postal Service.
  
  
• SNMP - Simple Network Management Protocol
  Protocol designed to allow for the monitoring and maintenance of network systems remotely.
  
  
• Socket
  Software structure operating as a communications and point within a network device.
  
  
• Source Address
  Address of a sending network device.
  
  
• SPID - Service Profile Identifier
  A number or set of numbers assigned to your ISDN line by your phone company. In the U.S., one SPID is assigned to each channel. The switch uses the SPIDs as unique identification numbers for each ISDN line, so it can determine where to send calls and signals.
  
  
• SSL - Secure Sockets Layer
  A security protocol that provides communications privacy over the Internet. The protocol allows client/server applications to communicate in a way that is designed to prevent eavesdropping, tampering, or message forgery.
  
  
• S/T Interface - Subscriber/Termination Interface
  The S/T Interface carries the signals between the terminal adapter and the NT-1.
  
  
• Stack
  A set of organized computer variables used to keep track of the various processes that are taking place inside a computer. Remote Access users create a TCP/IP stack when they connect, on their local systems to keep track of the communication processes being carried out between their system and the Internet.
  
  
• Static Route
  A route that is manually entered into the routing table. Static routes take precedence over routes chosen by all dynamic routing protocols.
  
  
• Subnet
  A portion of a network, which may be a physically independent network segment, which shares a network address with other portions of the network and is distinguished by a subnet number. A subnet is to a network what a network is to an internet.
  
  
• Subnet Address
  The subnet portion of an IP address. In a subnetted network, the host portion of an IP address is split into a subnet portion and a host portion using an address (subnet) mask.
  
  
• Subnet Mask
  A 32-bit addresss mask used in IP to specify a particular subnet.
  
  
• Subnetwork
  A collection of end systems and intermediate systems under the control of a single administrative domain and utilizing a single network access protocol.
  
  
• Switch
  Telephone company switching device which "makes the connection" when you place a call. Modern switches are specialized computers. ISDN service is provided from a "Digital" switch, most commonly an AT&T model "5ESS", Northern Telcom model "DMS-100", or Siemens model "EWSD". The switch, and related software running on it, will determine which ISDN protocol(s) will be available to customers connected to it. See also PBX.
  
  
• Switched-56
  A type of digital telephone service developed in the mid 1980's which allows dialing on a single 56Kbps line. Each switched-56 circuit has 1 or 2 copper wire-pairs associated with it. Switched-56 is being rapidly replaced with ISDN, which is cheaper and more flexible.
  
  
• Synchronous Data
  A form of serial data which uses a clock signal to synchronize the bit stream. Since, unlike asynchronous data, no start and stop bits are used, data throughput is higher than with asynchronous data. ISDN uses Synchronous data.
  
  
  T
  
  
• T1 - Transmission 1
  24 x 64Kbps channels giving a total of 1.356Mbps.
  
  
• T3 - Transmission 3
  A transmission link that has a data rate of 45 Mbps.
  
  
• TA - Terminal Adapter
  The terminal adapter is the hardware used to connect your computer or network to the ISDN line. It may be internal (a card that fits into a slot inside your computer), or external (a separate piece of hardware that plugs into one of the serial ports on the back of your computer). A terminal adapter may be built into an ISDN telephone for dumb terminals. Terminal adapters may also be used to convert an analog protocol into the ISDN interface, enabling you to use an existing analog modem or fax machine.
  
  
• Tandem Switch
  The telco switch that your long distance call gets routed to, which then routes your call to your selected IEC.
  
  
• Tandem Trunks
  The telco trunks that connect between your local switch and the tandem switch. Tandem trunk problems will cause difficulties regardless of the IEC selected.
  
  
• TCP - Transmission Control Protocol
  TCP corresponds to layer 4 (the transport layer) of the OSI reference model. It provides reliable transmission of data. It's an Internet Standard defined in STD 7, RFC 793. It is connection- and stream oriented, as opposed to UDP.
  
  
• TCP/IP - Transmission Control Protocol over Internet Protocol
  This is a common shorthand which refers to the suite of transport and application protocols which runs over IP.
  
  
• TD - Transmit Data
  Data coming from the DTE towards the DCE or network. Also, a light on a modem or CSU/DSU which lights to indicate presence of this signal.
  
  
• Telco
  Telephone Company. Your local telephone service provider.
  
  
• Telnet
  The Internet standard protocol for remote terminal connection service.
  
  
• Terminal Emulator
  An application that configures a computer to act as a connection to a mainframe based system. This can be accomplished with Chameleon TN3270 application.
  
  
• TFTP -
  A simple form of the File Transfer Protocol (FTP). TFTP uses the User Datagram Protocol (UDP) and provides no security features. It is often used by servers to boot diskless workstations, X-terminals, and routers.
  
  
• Throughput
  Rate of information arriving at, and possibly passing through, a particular point in a network system.
  
  
• T-Interface
  BRI ISDN delivered over two wires. This interface works at loop lengths up to 18,000 feet.
  
  
• Token
  A control information frame, possession of which grants a network device the right to transmit.
  
  
• Token Ring
  A token ring is a type of LAN with nodes wired into a ring. Each node constantly passes a control message (token) on to the next; whichever node has the token can send a message. Often, "Token Ring" is used to refer to the IEEE 802.5 token ring standard, which is the most common type of token ring.
  
  
• Topology
  A network topology shows the computers and the links between them. A network layer must stay abreast of the current network topology to be able to route packets to their final destination.
  
  
• Trailer
  Control information appended to the data in a packet.
  
  
• Transceiver - Transmitter Receiver
  The physical device that connects a host interface(i.e.Ethernet Card) to a local area network, such as Ethernet. Ethernet transceivers contain electronics that apply signals to the cable and sense collisions. Remote Access users using an ISDN connection use an ISDN card as a transciever for the digital signal being sent to and from the computer. Typically, transceivers are found between the end of an input cable and a computer.
  
  
• Transport Layer
  Layer 4 of the OSI reference model. The transport layer is responsible for reliable network communication between end nodes. It implements flow and error control and often uses virtual circuits to ensure reliable data delivery.
  
  
• Trumpet Winsock
  A Windows Sockets 1.1 compatible TCP/IP stack that provides a standard networking layer for many Windows networking applications to use, and has itself been a major vehicle in achieving widespread use of Windows Sockets 1.1.
  
  
• Trunk
  A telephone "carrier" facility between 2 telephone COs, between a CO and a IEC's POP, or between a private switch (PBX) and the CO.
  
  
• Trunk Line
  A communications line connecting two Frame Relay switches to each other.
  
  
• TSR - Terminate and Stay Resident
  A type of program that is loaded into a computers memory and stays active while other programs are being run. The TSR runs in the background, while other applications run in the foreground.
  
  
• TTL - Time-to-live
  One of the parameters in an IP packet is the time to live. This parameter specifies how long, in number of hops, the packet will survive. If the time to live expires (reaches zero), the packet is discarded.
  
  
• Tunnelling
  Refers to encapsulation of protocol A within protocol B, such that A treats B as though it were a datalink layer. Tunnelling is used to get data between administrative domains which use a protocol that is not supported by the internet connecting those domains.
  
  
• Twisted Pair
  Cable made up of a pair of insulated copper wires wrapped around each other to cancel the effects of electrical noise.
  
  
  U
  
  
• UDP - User Datagram Protocol
  An Internet Standard transport layer protocol defined in STD 6, RFC 768. It is a connectionless protocol which adds a level of reliability and multiplexing to IP.
  
  
• U Interface
  A two-wire (single pair) interface from the phone switch to your premises. A terminal adapter with a U Interface has a built-in NT-1.
  
  
• UNIX
  A computer operating system (the basic software running on a computer, underneath things like word processors and spreadsheets). UNIX is designed to be used by many people at the same time (it is "multi-user") and has TCP/IP built-in. It is the most common operating system for servers on the Internet.
  
  
• URL - Uniform Resource Locators
  A URL provides a consistent format for referencing any one of a number of information servers such as FTP and Web servers.
  
  
• Usenet - NetNews
  A collection of thousands of topically named newsgroups, the computers which run the protocols, and the people who read and submit Usenet news. Not all Internet hosts subscribe to Usenet and not all Usenet hosts are on the Internet.
  
  
• User ID
  A unique number used to identify you on the network. Remote Access users are assigned a user id that doubles as their account id.
  
  
• Username
  A unique "name" by which each user is known to the system. This name is given to the user whenever they register to use the system.
  
  
• UUCP - UNIX to UNIX Copy Protocol
  This was initially a program run under the UNIX operating system that allowed one UNIX system to send files to another UNIX system via dial-up phone lines. Today, the term is more commonly used to describe the large international network which uses the UUCP protocol to pass news and electronic mail.
  
  
  V
  
  
• V.35
  A serial data interface for synchronous data. V.35 uses balanced signal and data lines.
  
  
• Veritas
  Backup storage. Protects against hardware failure, malicious data modification, natural disaster, and version upgrade rollbacks.
  
  
• Virtual ISDN
  An alternative to repeaters which uses a local Telco switch to act as a repeater and which then sends the signal onto another switch that supports ISDN.
  
  
  W
  
  
• WAIS - Wide Area Information Servers
  A distributed information service which offers natural language input and indexed searching of large databases of information from remote systems.
  
  
• WAN - Wide Area Network
  A network, usually constructed with serial lines, which covers a large geographic area.
  
  
• WHOIS
  An Internet program which allows users to query a database of people and other Internet entities, such as domains, networks, and hosts, kept at the DDN NIC. The information for people shows a person's company name, address, phone number and email address.
  
  
• Workstation
  A networked personal computing device with more power than a standard IBM PC or Macintosh. Typically, a workstation has an operating system such as UNIX that is capable of running several tasks at the same time. It has several megabytes of memory and a large, high-resolution display.
  
  
• WWW - World Wide Web (Also Called W3)
  The WWW is the global collection of web servers and the HTML documents contained on them. A Hypertext-based, distributed information system created by researchers at CERN in Switzerland. Users may create, edit or browse Hypertext documents. The clients and servers are freely available.