ABB: Above Board BUSES: 4 MITEL ST buses [each 32 DS0's x 4=128 DS0's]; only 1 of the 4 is selectable, by software on the FDC 386 card. The Franklin Above Board Bus has a 20-pin header connec­tion with two connectors provided on each card for daisy-chaining the signals from card to card. Each 20-pin connector is wired in parallel to the other so that it does not matter which connector is used. A 20-pin flat ribbon cable is used to make connections from card to card.

Access: The process of getting data from or putting data in storage.

Access Method: 1} The process, the hardware/software method of moving data between remote devices and host-resident applica­tions. 2} The method used by LAN/network stations to determine when stations can transmit on the network.

Address: 1}The unique identity of a station on a network; or the identity of a network.

Accounting Management: One of the 5 categories of network manage­ment defined by the ISO.

AIX: Advanced Interactive eXecutive. IBM's UNIX.

ANSI: American National Standards Institute.  Devoted to the devel­opment of voluntary standards that will enhance the productivity and international competitiveness of American industry. ANSI.SYS is a configuration file with instructions for displaying informa­tion according to an ANSI recommendation on screen control. Basically, network hosts expect terminals to be ANSI compatible. See VT100.

API: Application Program Interface. A defined set of interfaces providing a means for one program to access another.

APPN: IBM's Advanced Peer to Peer Network; equivalent to a routing layer for SNA.

ARCS: Advanced RISC Computer Specification

ARCnet: A popular LAN by Data Point

ARP: Address Resolution Protocol, a special [TCP/IP] protocol used to solve the problem of mapping Internet addresses to physical addresses. ARP converts Internet addresses to Ethernet addresses.

ARPA: Advanced Research Projects Agency; a US Government DOD agency which sponsors research in new technology; e.g., ARPANET, the original Packet Switched Network. Now also known as DARPA, and DARPANET.

ASCII: American Standard Code for Information Interchange. A stand­ard 8-bit information code used with most computers and data terminals. If all eight bits are used as information bits, 256 characters are possible (as with EBCDIC). Some systems do not use the eighth bit of the code, and it is assumed to be a logic one at all times. Some systems use the eighth bit for a parity bit (odd for synchronous transmission; even for asynchronous). Seven bits of information provide for 128 possible characters. A new 16 bit Unicode is being devised by the combined work of several international groups. With 16 bits, it is possible to define 65536 different characters in a single scheme. This single Universal Code will be able to have all of the many different characters and special characters needed in the different natural languages.  About 27000 are now defined.

Asynchronous transmission: A mode of data transmission with no clock or sync pulses in which the time intervals between transmitted characters may be of varying, uneven length; also called start- stop transmission, it most commonly occurs over terminal lines.

ASE: Application Service Element; the basic Application Layer mechanisms for exchanging information between open systems. Each ASE performs a single type of information exchange: message handling, file transfer, virtual terminal.

AT (ISA) Bus: The bus of the first IBM AT in 1984. 8 MHz, with 16- bit data and 24-bit address buses.

ATM: Automatic Teller Machine.

ATM: Asynchronous Transfer Mode - source and destination are not synchronized in time (CCITT's name for Fast Packet).

AUI: Access Unit Interface.

Backbone: A Networking term, an OSI term which means: a main support or major sustaining factor. The OSI BACKBONE spans both local and wide area networks (LANs & WANs) as well as facilitating the interoperability among systems using the network. TheT1 backbone refers typically to sharing of independent data or voice networks over a single, physical "T1" line leased from a telephone compa­ny. The economy of scale of a WATS (Wide Area Telephone System) are achieved but there is no ability for the independent networks to connect or interoperate with each other. The FDDI backbone and the Ethernet backbone support local area communications but do not necessarily allow systems to communicate unless all are running the same networking protocols. On a PDN (Public/Private Data Network) the term usually infers the protocol used, such as X.25 or Frame Relay, as well as the circuitry.

Bandwidth: The range of frequencies assigned to a channel; i.e., the difference between the highest and lowest frequencies of a band, expressed in Hertz. Voice Bandwidth is approximately 4000 Hertz.

Baseline: The Baseline is the initial version of a computer program or program system released to the customer/user.  It contains the initial set of capabilities, is in stable operating condition and is usually numbered 1.0. Successive upgrades are major Version Releases that contain whole new capabilities and increment the number before the decimal point i.e., 3.0, 4.0 etc. Revision Releases contain minor corrections or changes to the Baseline Version and change the number after the decimal point, i.e., 1.1, 1.3, 2.2, 3.3. Changes made in the Revisions are incorporated into a new stable Baseline Version; hence Version Releases are referred to as Baseline Versions; Revision Releases are not.

Baud Rate: A type of measurement of data flow in which the number of signal elements per second is based on the shortest element.  When each element carries 1 bit, the baud rate is numerically equal to bits per second (bps). If an element carries 2 bits, 2400 baud = 4800 bps, etc.

BBN: Bolt, Beranek and Newman. Developer of the original ARPANET.

BISDN: Broadband ISDN; see ISDN.

BNA: Burroughs Network Architecture - comparable to SNA

BNC: Bayonnet Neill Concelman; A common type of connector used in antenna, cable, and radios; named for its originator.

bps: bits per second; in serial transmission the speed with which a device transmits data; used to indicate the speed of a modem.  See Baud rate.

BRI: ISDN Basic Rate Interface = 160 Kb/s;  Ports 2B + D = 160 Kb/s MAX: B=64 Kb/s, D=16 Kb/s + 16 Kb/s framing; used to serve termi­nals or other low capacity devices.

Bridges: Bridges operate at OSI layers 1 & 2; they employ no Network Layer protocol and cannot support direct X.25 links. They can "straddle" two LANs, "listen" to both and forward only those packets addressed to the opposite LAN.

BSC: Bisynchronous; an IBM data link control protocol where each block begins with 2 sync characters.

BTAM: Basic Telecommunications Access Method, an IBM product that interfaces between a network and host applications.

Bug: Any mechanical, electronic or software defect that interferes with or bugs up the operation of equipment or software.  A mal­function in operation, or mistake in design. There were "Bugs" in things from the very beginning; there was a fly in the oint­ment as soon as there was ointment. Autos and airplanes, radios and radars had "bugs" or were "bugsy" (not buggy) long before the invention of modern computers and software. ("Analytical en­gines" too, that's why they never worked.) For equipment, one "works the bugs out". For software, one"Debugs".

Bus, Buss: A set of parallel wires over which data is communicated. Buses may be internal to a CPU, may connect a CPU to main or secondary memory, or may connect a computer to peripheral equip­ment. See PC Bus, AT (ISA) Bus, EISA Bus.Buzz: Noun: A rapidly humming, vibrating or droning sound; verb transitive: to cause to buzz; verb intransitive: to make a low droning or vibrating sound like that of a bee

Buzzword: Any arcane or jargon word or term used with intent to baffle, beguile or buzz the listener. Always to be questioned.

C: A high-level programming language developed in 1972 at Bell Labs as a follow-on to the earlier "B" language.  It is ALGOL based and designed to provide programming constructs such as condition­al branching, looping, intricate data structures as well as low- level programming constructs which makes it well suited to sys­tems programming. The original UNIX at Bell Labs was written entirely in C and almost all UNIX systems include C compilers, which means that C source code is transportable across almost all UNIX systems.

CAD/CAE/CAM: Computer Aided Design/Engineering/Manufacturing

CAM: Content Addressable Memory

CC: Country Code. A 2 or 3 character code to identify thecalled country; included in a Data Network Identifer Code (DNIC).

CCITT: Comité Consultatif International Télégraphique et Téléphonique. The international consultative committee estab­lished by the UN that sets international communications usage standards that are followed in Europe and elsewhere, but not always in the USA. TheCCITT interface is a UN communications standard that is considered mandatory in Europe and other conti­nents. It is much like the US EIA Recommended Standard RS 232-B in the USA. This standard is accepted as an interface require­ment between data processing equipment (a computer) and Data Communications Equipment (DCE, a modem) or Data Terminal Equip­ment (DTE, a terminal, or a computer). (See EIA or RS 232). For example, CCITT V.22 bis defines the worldwide standard for send­ing 2400 baud data over analog/voice telephone lines; CCITT X.25 is a packet switching protocol.

CCSS: Common Channel Signaling System (CCITT No. 7) (SS#7)

CD-Video: Compressed Digital Video; Video signals contain a large amount of redundant information that can be eliminated without degrading the picture. There is redundancy within a video frame and redundancy between frames. There may be large areas of the same color or intensity within a frame which can be encoded once in order to transmit the information only once for the area; this is intraframe compression. Interframe compression is encoding of redundant information between frames.. 

CEPT: Conference of European Post and Telecommunications; a body that sets policy for services and interfaces for 26 countries.

Channel: A means of transmission. A logical path over which data is transmitted, usually identified by a unique (logical or physi­cal) channel number.

Channel Bank: A voice Time Division Multiplexer which provides carrier conversion between the voice channel and a T-1 digital circuit and vice versa. The original D-1 channel bank handled one frame at a a time. The D-4 channel bank utilizes a 12-frame sequence called a superframe. The superframe uses stolen bits (from the 6th and 12th frame) for status, and the 193rd bit for superframe framing bits. The D-4 channel bank can handle either two T-1s or four T-1s, allowing either 48 or 96 separate 64 Kb/s channels within the same channel bank. In jargon usage between professional schannel bank usually refers to voice while multi­plexer refers to data.

Circuit: 1} In electronics, the complete path of an electric cur­rent including the generating apparatus, intervening resistors, capacitors, etc. See IC, Integrated Circuit. 2} In a system, the communication path between nodes. Circuits operate over physical lines and are the medium on which all input/output occurs.

CISC: Complex Instruction Set Computer. A CPU that can recognize and execute a large number of instructions. Most microprocessors are CISC chips. See RISC.

Clear Channel: Permits transmission of D-1 signals with no restric­tion on the number of consecutive zeros using the B8ZS (Binary Eight Zero Substitution) technique.  B8ZS uses bipolar violations to replace strings of 8 consecutive zeros with a special pattern, thus assuring timing --i.e., synchronization-- pulses regardless of data. B8ZS does not introduce errors, avoids the 15 consecu­tive zeroes restriction and provides a "clear channel" capabili­ty, which allows all of each 64 kb/s DS-0 bandwidth to be used for data transmission, hence all of T-1.

CLNP: ConnectionLess Network Protocol; OSI datagram protocol: each packet is sent through the network separately, and is free to take the best available path; also called the "send and pray" method.

CLNS: ConnectionLess (Oriented) Network Services, a UNIX feature

CMIP: Common Management Information Protocol. An OSI-based Proto­col that provides standard ways to manage l;large multi-vendor networks.

CO: Central Office (of the local telephone company)

CODEC:  Coder/Decoder (Analog/Digital Converters)

Voice CODEC: Voice Digitizer; Video CODEC: Video Digitizer.

Concentrators/converters

CONS: Connection Oriented Network Services, a UNIX feature

COS: Corporation for Open Systems - an independent, non-profit consortium of vendors and users committed to the development of consistent, OSI-based conformance tests.        

COTS: Commercial Off The Shelf. Hardware or Software available commercially.

CP: Customer Premises (not the CO)

CPE: Customer Premise Equipment

CUA: Common User Access

CRC/LRC/VRC: Cyclic/Longitudinal/Vertical Redundancy Check

Cyclic Redundancy Check (CRC): A cyclic parity check character for longitudinal error control calculated from a divisor polynomial. A CRC character is usually appended to a block of data that is stored on disk or tape, or transmitted over a communication network for error detection and correction.

CSMA-CA/CD/CR: Carrier Sense Multiple Access--Collision Avoidance/ Collision Detection/ Collision Resolution. See Ethernet.

CSPDN: Circuit Switched Public Data Network 

CSU/DSU: Channel Service Unit (Once called NTCE: Network Channel Terminating Equipment) is a line driver with a pair of transmit wires and a pair of receive wires. The CSU/DSU is the device that interfaces the user's DTE to the digital line instead of a modem. The CSU/DSU are repeaters; the CSU is capable of transmitting 6000 feet, about a mile, while the DSU can transmit about 600 feet.

D-MARK Channel Bank: A T-1 24 analog loop start CO ports. Made by FTC. Also a term used to define the telco end connection at the customer premises.

D4: Channel Bank which uses Super Frame.

DACS: Digital Access & Cross Connect System, a device which allows multiple channels of T-1 or T-3 circuits to be integrated into any desired combination of other T-1/T-3 circuits for routing purposes. A 1/1 DACS can reroute input T-1 channels to other T-1 channels for output. A 3/1 DACS can integrate T-1 channels with T-3, and a 3/3 DACS can intermix T- 3 channels.

DAL: Data Access Language; lets DOS PCs and MACs access UNIX based SQL databases in a client-server configuration.

DARPA: DOD ARPA; see ARPA.

DASD: Direct Access Storage Device.

DataCom: Data Communications: The term encompassing transmission, switching, storage, and control of data in a network. Transmis­sion is the function of channels, circuits or links. Switching requires the activation of a path, a connection, between two stations or points to allow a conversation. Control includes the signal conversion that takes place between the terminal and modem, from digital to analog, and back again, error detection and correction; line management and control procedures. See OSI, TeleCom.

Connection: fixed point-to-point, multipoint, or switched point-to-point. Identification of sender and receiver. Message handling: transfer and delivery of message from sender to receiver. Termination: releasing the resources from their temporary assignment; disconnecting sender and receiver and returning the  system to its initial state.

Datagram: A packet of varying size used on networks. A self- contained block of data carrying enough information to be routed from source to destination.

Data Encryption: Encrypting data converts it to an unintelligible form called cipher. Decrypting cipher converts the data back to its original form. The Data Encryption Standard algorithm from the National Bureau of Standards specifies both enciphering and deciphering operations which are based on a binary number called a key which consists of 64 bits, of which 56 are used by the algorithm and 8 for error detection. The key is generated in such a way that each of the 56 data bits are random. Data can be recovered from cipher only by using exactly the same key used to encipher it. A standard algorithm based on a secure key thus provides a basis for exchanging encrypted computer data by issu­ing the key used to encipher it only to those authorized to have the data.

Data Link Control (DLC): A bit-oriented protocol or procedure (contrasted with character-oriented), a line discipline; a set of rules to insure the orderly transfer of information between interconnected nodes of a network. Various standards have been established. ADCCP (Advanced Data Communications Control Proce­dure) is the ANSI standard; HDLC (High-level Data Link Control) is the original ISO standard; SDLC (Synchronous Data Link Con­trol) is IBM's standard. Protocols written to satisfy the second layer of the ISO/OSI DLC are also called Link Access Procedures (LAP). HDLC & SDLC are known as LAP "A" (for asymmetric); ADCCP, CDCCP, BDLC & UDLC, (definitions not known), and other newer ones are called LAP "B" (for balanced) dialects. All dialects togeth­er are called XDLC. CCITT Recommendation is X.25. See protocol.

Data Organization: Data is organized in increasingly complex enti­ties:bits, bytes, fields, records, files anddatabases where each consists of one, or more, of the previous entity.

Bytes are usually 8 bits;Fields are named collections of bytes;Records are named collections of fields; andFiles, kept on secondary storage, are named collections of records - usually of one type, each uniquely identified by a record ID that never changes while the record exists. 

FILES are organized as: Flat Sequential, Sorted Sequential and Indexed Sequential. Sequential means:

1. In the SEQUENCE in which records are written; files thatmust be searched sequentially because no order has been established are calledFlat Files; Sequential Access Methods (SAM) are used to locate records.
2. SORTED; where order is established and maintained by sorting the records on the primary key (sort key), e.g., in numeric ascending or descending order, alphabetic order. Binary search techniques are used to locate records whose primary key is known.3} INDEXED; where each record is given an index/key field. When an INDEXED file is built, a table called an INDEX is created where each entry contains a key value and pointer to the location in the file where the record with the key value is located. As each file record is added, its entry is created for the INDEX.  Multiple INDEXES may be constructed for accessing a single file.  A file can be both SORTED and INDEXED.  Even though a file is INDEXED, if searches (queries) are based on non- indexed fields, the file must be searched sequentially, hence Indexed Sequential Access Methods (ISAM) are used to locate records.

DATABASES nowadays are NON-RELATIONAL or RELATIONAL:

NON-RELATIONAL DATABASES are composed of:

1. Inverted Lists which are INDEXED files. Each INDEX is kept sorted on the values of its INDEX key, or else it also must be searched sequentially.All searches use INDEXES. This process of accessing the file through the INDEX instead of sequentially examining the records is said to be inverted access, and hence an indexed file is called an Inverted List. Files which use every field as an INDEX are said to be fully inverted.
2. Hierarchic files which are organized in a tree structure with parent/child (or node/leaf) relationship where each parent may have many children but each childmay have only one parent. The connections from a parent to a child record and visa versa are defined through pointers in the records.
3. Network files which have hierarchic organization that allow children to relate to many parents.

RELATIONAL DATABASES are composed of logical structures called Relations perceived by the user as tables; as parallel, single element tables or columns. A characteristic of relational sys­tems is called the view, one way of looking at related data in a group of relations/tables; i.e., at the totality of data seen by the user at a chosen time.  If a set of relations is a set of parallel single- element tables, then a view is the related data extracted from those tables from a particular angle, e.g., a row: a unique set of data extractable from the tables using the same vertical index value (in the same row down from the top). 

  The RELATIONAL model is a logical structure rather than a physi­cal one; hence the principles of RELATIONAL databases can be discussed conveniently without necessarily concerning oneself with the physical implementation of the data structures. The tabular representation used in the RELATIONAL scheme is easy for users to comprehend and easy to implement in the physical data­base system.

  All early database systems were NON-RELATIONAL. They were de­veloped empirically rather than on the basis of pre-defined abstract models. Models were defined after the event by induc­tion from the existing cases. Since the presentation of the RELATIONAL model (E.F. Codd CACM 1970) -- the most important development in the history of the field -- almost all database systems are Relational or said to have Relational attributes. This is because it is relatively easy to convert virtually any other type of database structure into the RELATIONAL scheme, or to represent it as a RELATIONAL model. Thus the scheme may be viewed as one form of universal representation.

DBMS: Data Base Management System, usually the software that con­trols the storing and retrieving of data; and often a particular set of software which is designed and developed using a particu­lar file structure and specialized techniques for storage and retrieval. 

DCE: Data Circuit-terminating Equipment. Data Communication Equip­ment (In non-X.25 usage, a modem.) A CCITT X.25 term referring to the network equipment that establishes, maintains and terminates a connection and handles the signal conversion and coding between the Data Terminal Equipment (DTE) and the network. The switching exchange of the network to which DTE's are connected.

DCE: (OSF's) Distributed Computing Environment.

DDN: Defense Digital Network

DDS: Digital Data Service [Dataphone Digital Service]: a four-wire leased circuit/service with connection to a digital network on an end-to-end basis. Available only where the local Telephone Company (Telco) Class 5 Central Office (CO) provides both a digital service and a connection to a carrier Point Of Presence (POP). DDS involves specific transmission rates: normally 2400, 4800, 9600 bits-/second, 19.2Kb/s and 56Kb/ssubrates, and 64Kb/s clear channel.

Dial Digital/Switched Digital:  Switched 56Kb/s or 160Kb/s; with 384Kb/s available for video services.

D&I: Drop & Insert {Multiplexer} At any of the points on a T-1 circuit, the D&I Multiplexer can remove/drop some DS0 channels and add/insert others. i.e., On a single T-1 end-to-end connec­tion, there may be different DS0 users at individual point-to- point connections.

Distributed Information System (DIS): Any nodal computer system involving multiple sites connected together by a communications net-work in which a user at any site can access data at any site. Characteristically, the multiple sites are locally dispersed and connected by aLAN, or geographically dispersed, connected by aWAN or "long haul" network and often use their own copy of the same DBMS. 

  A DIS design involves three levels of sophistication: 1}Distrib­uted Processing: The implementation of one set of logical func­tions in multiple physical devices. 2}Distributed Data Base: One logical set of data files stored at multiple physical locations within the system. The distribution of the data base poses many systems challenges, including the definition of the primary files needed to reestablish "primacy" in the case of mutations and discrepancies in the data. 3}Distributed Operating System: which distributes both data base processing and network control. This embraces such features as downline loading of files and software for unattended operations, and total network control.

DME: (OSF's) Distributed Management Environment.

DNA: DEC/Digital Network Architecture - comparable to SNA 

DNIC: Data Network Identifier Code, Includes theCC andPDN to iden tify thecalled country andPublic Data Network.

DOD: Department Of Defense 

DOS: Disk Operating System, a disk resident operating system. In the 1960s and 1970s each major computer manufacturer developed its own DOS for use on its own computers. When the IBM PCs (Personal Computers) came on the market in the 1980's, PC DOS (IBM) and MS DOS (MicroSoft) were developed as single user, single tasking operating systems especially for IBM PCs or IBM compatible PCs. 

DRAM: Dynamic Random Access Memory - must be refreshed to retain values.

DRDA: Distributed Relational Database Architecture.  A critical element of IBM's Systems Application Architecture (SAA). that will enable the sharing of data among applications regardless of the location of the data or the platform on which the application runs.

DS1 signaling: for each of the 24 separate T-1 channels, Pulse Code Modulation (PCM) is used to sample the voice signal 8000 times per second for conversion to binary digits (bits) and each sample generates one 8-bit byte of information. For transmission, aframe is established, with 1 byte from each channel, of (8 x 24 =) 192 bits with an extraframing bit added for synchronization, making the total 193 bits. 8000 frames/second times 193 bits = 1,544,000 bits/second = T-1 transmission rate. Another definition of Full T-1 is that the service transmits 24 logical channels using Time Division Multiplexing (TDM); each channel transmits at 64 Kbps.

DS0: Digital Signal - Level Zero:   64 Kb/s 1 Voice Channel

DS1: Digital Signal - Level One: 1.544 Mb/s (24 DS0s = T-1 rates)

DS2: Digital Signal - Level Two: 6.312 Mb/s (4 T-1s)

DS3: Digital Signal - Level Three: 44.736 Mb/s (28 T-1s)

DS4: Digital Signal - Level Four: 274.176 Mb/s (4032 DS0s)

DSP: Digital Signal Processor; a chip designed to solve a specific algorithms.

DSU:  Digital or Data Service Unit: functions as the Telco digital interface to the DTE from the T-1 carrier Channel Service Unit (CSU), but cannot be implemented as a standalone unit. It is connected to a CSU by a 15 pin cable, or often, combined in the same device with a CSU. See CSU.

DSX: Digital Switching Exchange

DTE: Data Terminal Equipment. A CCITT X.25 term referring to the user's computer or terminal equipment connected to a Data Cir­cuit-terminating Equipment (DCE=MODEM) on a packet switching data network for the purpose of sending and receiving data.

Duplex: Pertaining to two, a pair, a two-in-one situation; sometimes it refers to a second set of identical (standby) equipment or facilities to be used during malfunction of the primary equip­ment.  It is sometimes used to mean a communications channel providing simultaneous transmission in both directions; i.e., full duplex. Full duplex requires a 4-wire circuit; i.e., two pairs of wires, one pair for each direction. Half duplex, using a 2-wire circuit, permits communication in either direction but only one at a time.

EBCDIC: Extended Binary Coded Decimal Interchange Code; an 8-bit character code established to extend--to double-- the 128 charac­ters available in the original 7-bit ASCII. All 8 bits are used for information to represent 256 unique letters, numbers and special characters.

EHF: Extremely High Frequency; in the range of 30,000-300,000 MHz.

EIA: Electronic Industries Association; An American trade associa­tion of the US electronics industry which formulates and publish­es technical standards, disseminates marketing data and maintains contact with US governmental agencies in matters relating to the electronics industry. Similar to the CCITT. The EIA interface is a set of signal characteristics for connection of terminals to modems, and specific physical coupler dimensions for use in USA. See RS 232.

E & M: Ear and Mouth

EISA: Extended Industry Standard Architecture; a high performance 32-bit, 33Mbytes/s bus architecture on the ISA bus with Multi- Master capability, 32-bit data and 32-bit address. The EISA connector is a superset of the ISA connector and fully compati­ble; that is, all PC and AT cards work in EISA systems without modification.

ESF: Extended SuperFrame; a transmission format which utilizes the framing (F) bits of two consecutive super frames to detect and isolate problems. D4 & ESF use 24 DS0 for data; see SuperFrame.

EtherNet LAN: A Local Area Network with broadcast topology on Coax­ial Cable, usually capable of linking up to 1024 nodes; the "ether" is a copper and plastic cable with high reliability and low cost.  The "ether"-- is abus, or astar -- to which all interfaces are attached. Originally developed by Xerox the term and concept are now in general use with a variety of different, incompatible, EtherNet protocols in existence. Thebus uses "Thick Ethernet" (type 10BASE5) a thick, stiff, 50 _ yellow cable; a "thin Ethernet" (10BASE2--cheapernet) a thin, flexible 50 _ cable; or a type 10BASE-T which uses an unshielded twisted-pair wire [10 Mb/s]. The star uses a fiberoptic or Unshielded Twisted Pair (UTP) cable. Ethernet is called Carrier Sense Multiple Access (CSMA) becausemultiple access (MA) points sense for carrier access (CS) to determine when the network is idle. When a node, i.e. an interface senses the network is idle, it may begin transmitting. Since 2 nodes may begin transmissions at the same time, a collision may occur. Sending stations monitor forcollision detection (CD) and abort if one is detected, hence Ethernet is called CSMA-CD. See LAN.

FDDI: Fiber Distributed Data Interchange, of fiber optic cabling with 100 Mbps network transmission speed.

FEP: Front End Processor

FIFO: First In, First Out; a method of storing and retrieving items in a stack, list, table or ship in which the oldest item (first in) is issued first. See LIFO.

FIPS: Federal Information Processing Standard, On 15 August 1990 FIPS 146 became a mandatory requirement for the procurement of Federal computer networking products and services. That is, it requires the use of GOSIP when bidding in the Federal sector. 

FITB: Fill In The Blanks. See Forms Displays.

Flat File: 1} A pure ASCII file, with no format control characters except perhaps Line Feed (LF) and Carriage returns (CR); a Word Processor ASCII text file is not a flat file. 2} A sequential file; see Data Organization.

FLOP: Floating Points/per second. TeraFLOP, gigaFLOP. 

Forms Based systems: communicate with the user by means of option menus and FITB (Fill In The Blanks) Forms displayed on the screen.

Forms Displays: A type of data entry display that provides for Fill In The Blank (FITB) operation. Data fields with protected field names and variable blank areas are displayed for operator manual entry or type-in of information. What now are called FITB Forms were once, and often still are, called "menus".

Four Wire: A 4-wire circuit permits full duplex transmission; i.e., two pairs of wires, one pair for each direction.  A 2-wire, half duplex circuit permits communication in either direction but only one at a time. See telecommunication.

Fractional T1: A service available in several speeds; Pac Bell offers 256 kbps, 384 kbps, 512 kbps, and 768kbps.

Frame: A unit of information. 1} In DS-1 (voice) signal transmis­sion, a frame contains 1 byte for each of 24 separate DS-0 chan­nels plus an extra bit called theframing bit [8 x 24 = 192 + 1 = 193 bits]. 2} In message transmission it varies in length, de­pending on the network. Each frame contains aheader and adata section. The header contains control information that helps the network deliver the frame to its destination.

Frame Relay: A wideband data service in WANs.              

FTAM: File Transfer, Access and Management is an ASE that transfers files, accesses remote files, and manages file operations. An ISO Application Layer protocol. 

FT Bus: Franklin's 4 ST Buses connected by ribbon cable. See ABB.

FTP: File Transfer Protocol - permits the transfer of both binary and text files between hosts on the network.

Gateways: Gateways implement all 7 OSI layers for two entirely different protocol stacks; a gateway is a sophisticated, multi- layered protocol converter.

GNAM: Gateway Network Access Method.

GOSIP: Government Open Systems Interconnection Profile. In 1988 Congress mandated that within two years a switch must be made to GOSIP from TCP/IP. GOSIP was developed by the US Government Users Committee and is comparable to MAP and TOP. The changeover mandates federal usage of interoperable protocols at all seven layers of the OSI and is definitely an upward evolutionary step from TCP/IP. TCP/IP was always considered to be an interim method of connecting networks together, with OSI being the ulti­mate goal. GOSIP will accomplish that goal.

GUI: Graphical User Interface 

HDLC: High-level Data Link Control

Hertz (Hz): unit of frequency equal to one cycle per second.

  1000 Hertz = kiloHertz (kHz); 1,000,000 Hertz = megaHertz (mHz) (megacycle). 1,000,000,000 Hertz = 1 gigaHertz, gHz (1 billion Hertz). See HF, VHF, UHF, EHF.

HF: High Frequency; in the range of 3-30 MHz.

HIPPI: High Performance Parallel Interface; an ANSI standard for data transmission at speeds between 800 mbps and 1.6 gigabits/s.

HSSI: High Speed Serial Interface.

Hub: The center of activity; the center of a wheel--where the spokes meet. A point on a network where many circuits are connected; on a LAN the hub is at the center of a Star network.

ICMP: Interface Message Control Protocol

IPN: Integrated Packet Network

ISA: Industry Standard Architecture. The ISA 8MHz bus architecture for PC expansion slots supports 8-bit or 16-bit data transfer and 24-bits for addresses; it is used for transfer of data between the PC motherboard and boards in these expansion slots.

Internet: Any singlevirtual network that joins together several independent LAN networks, by the technology ofInternetworking. Problems are: 1} different network technologies use different frame formats and 2} network addresses are not globally unique.

Internet Datagram: A universal packet used onInternets.

IP: Internet Protocol - transmits blocks of data (Internet datagrams or packets) over the network.

IPX: Internet Packet eXchange - an IP routing protocol more effi­cient than RIP.

ISDN: Integrated Services Digital Network. A planned European widedigital network with a very wide bandwidth for transmission of both data and voice. Basic rate is 144kbps for small capacity installations, and Primary rate is 1536kbps or 1984kbps for large capacity installations. Eventually, it will, replace the 3600 baud analog telephone systems now in use. ISDN is based on 3 principles: 1} digital connectivity for information transfer, 2} Common channel signaling, and 3} multi-purpose user-network interfaces. B-ISDN: Broadband Integrated Services Digital Net­work.

ISO: International Standards Organization

IVD: Integrated Voice/Data system

IVR: Interactive Voice Response; a telephone service which allows a person to talk with a computer via a Touchtone telephone. The IVR unit answers the call, greets and guides the caller through possible responses with a series of voice prompts which can be prerecorded words, phrases or computer generated speech.

Kernel The inner, or central part: the nucleus. The core portions of an operating system that perform the most primitive and essen­tial functions of that system; such as memory management, basic I/O, and task scheduling and switching. 

LAP A Link Access Protocol - Asymmetric

LAP B: Link Access Protocol - Balanced

LAP D: Link Access Protocol - D channel

LAN: Local Area Network. A LAN is a communications network designed to handle a limited geographic area, generally a single building or adjacent buildings. LANs are frequently defined in terms of "topology", "media" and "access procedure". The two most common LAN topologies are "broadcast" and "sequential". In a broadcast topology, all connected devices receive all messages at approxi­mately the same time. A bus and a star network are examples of broadcast topologies.  In a sequential topology, messages are passed from one device to another. A ring is an example of a sequential topology. LANs that use the bus architecture permit nodes to be hooked onto coaxial cable via taps. Repeater nodes are placed at the ends of the cable to allow extension of the network, or along the cable to permit branching of the network.

  The four most common LAN media are "twisted pair", "baseband coaxial", "broadband coaxial", and "fiber optics". A "broadband coaxial" medium permits multiple simultaneous signals. See Ethernet LAN.

LATA: Local Access and Transport Area; an area in which only one Telco is involved, usually one metropolitan area or one state.

LEC: Local Exchange Company (Telco, Telephone Company)

LIFO: Last In, First Out; a method of storing and retrieving items in a stack, list, table or ship in which the newest (last in) item is issued first. See FIFO.

Local Loop: That portion of the telephone circuit between each customer and the CO.  Originally the "loop" of copper wire be­tween the CO battery to one customer, back through the office to the other customer, and back to the battery at the CO.

Long Haul: A communications network where dispersed sites are linked by telephone lines and the typical data rate is 50 kbps or less.

MAC: Media Access Control, a sublayer of the OSI data link layer.

MAN: Metropolitan Area Networks

MAPI Messaging API, Microsoft's message access to Windows.

MAU: Media Access Unit

Message Switching: A method of transmitting messages over communica­tions lines in a network. The message is usually divided into blocks to facilitate error detection and correction.  The desti­nation is contained in the Message Header. The entire message is transmitted to the next node on the routing list, or next closest in the direction of the recipient. At each intermediate Store- and-Forward node, when all blocks are received correctly, the message is stored in case of the need to retransmit, and then forwarded towards its destination. 

MHS: Message Handling Systems

MIB: Management Information Base

Micro Channel: The Micro Channel Bus is designed to support an open architecture is configurable via Programmable Option Select (POS), provides Multi-Device arbitration, and like the EISA bus, Multi-Master capability,.

MIPS: Millions of Instructions per Second. A quick "raw horsepower" measure of CPU performance. Earlier comparisons were made on memory cycle times, or "add times"; the time it took to execute a single ADD instruction.

Mobile means internal power source for moving; movable means trans­portable or relocatable with external power for moving.  Moving means in motion; non-moving means fixed, mobile or movable.

MODEM: Modulator/Demodulator; a device that converts/modulates digital data to analog data for transmission and vice versa [demodulates analog data to digital data for reception].

MODEM Eliminator: A device that allows two DTE devices to be con­nected without using modems.

MOP: Maintenance Operation Protocol.

MOTIF: A Windows like environment for UNIX

MPC: Multimedia Personal Computer

MPR: Multi-Protocol Router

MTA: Message Transfer Agent; the X.400 MHS function that relays and delivers messages.  The other X.400 MHS function is the User Agent.

Multiplexer; Mux:. A device that takes low-speed inputs from a number of terminals and combines them into one stream for trans- mission on a single channel.Multiplexing: A grouping or regroup­ing of signals into a one-way transmission; the combining of many individual data streams onto a single transmission medium.

Multi-processing system: A computer architecture with a single CPU and multiple peripheral processors, or multiple CPUs. Multiple processes can be in operation simultaneously, i.e., in parallel.

Multi-programming System: An Operating System that divides the available processing time of a single CPU equitably among multi­ple programs, often related tasks of the same software system. One general strategy is to subdivide each processing second intotime slices and allow each program an equal number of time slices for execution; another is to run a program until input/output to a peripheral is invoked, then while waiting for the I/O to com­plete, switch the CPU to another program; however, only one program is in operation at any time. Used on large computers since the 1960's.

Multi-tasking System: A methodology in multi-user, multi-tasking systems to make it appear to each user that the computer is running only their task. Word Processing of one document can be in execution in the Foreground and printing of another in execu­tion in the Background. In reality, the single CPU use is inter­leaved, switched, between users or tasks in a multi-programming fashion. Available on PC's only with UNIX/XENIX or advanced versions of DOS.

NCP: (IBM's) Network Control Program; the Operating System of IBM 37xx communication controllers. 

NCP: (Novell's) Netware Core Protocol; a datagram delivery protocol for files across WANs.

NCS: Network Computer System; an protocol for remote procedure calls between computers on a network.

Netview: IBM's LAN Network Management software

NFS: Network File System; an industry-standard protocol that allows different kinds of computers to share files.

NIST: National Institute of Standards & Technology

NLSP: NetWare Link Services Protocol, a NetWare protocol based on OSPF to direct traffic away from failed links.

NOS: Network Operating System; a PC based OS that provides a basic set of functions for LANs such as file-sharing user security and printing services.

NPSI: NCP (Network Control Program) Packet Switching Interface; IBM's SNA to X.25 connectivity program. NPSI runs under NCP and converts the communications controller into a DTE.

NIU: Network Interface Unit; a board with a distinct address that plugs into each device on a LAN. It enables normally incompatible asynchronous and synchronous devices to communicate with each other over the same network.

NREN: National Research and Educational Network

NUA: Network User Address

ODBC: Open Data Base Connectivity. Microsoft's SQL call-level interface.

OC: Optical Carrier; OCs operate at various bandwidth: OC-1, OC-3 = 155.52 Mb/s, OC-12 = 622.08 Mb/s; OC-48 = 48 DS 3’s

ONCA: (Sun's) Open Network Computing Architecture

Open Systems Architecture: OSA.  Open architecture means a computer system in which all of the system specifications and interface descriptions are made public so that other companies can develop add-on products and adapters for the system. An open-architec­ture system generally has an open bus--one whose expansion bus readily accepts adapters--but not all systems with open busses have open architectures. The Apple Macintosh is an example of the latter.

OSF: Open Software Foundation

OSI: Open Systems Interconnection/Interface.  An international standard for the interface between a computer/terminal and a network, established by the ISO (International Standards Organi­zation) and IEEE (Institute of Electrical and Electronic Engi­neers). The OSI reference model separates the interconnection process into seven (7) distinct layers/levels and defines commu­nications rules or protocols for each of the layers:{1} Physi­cal, describes the electrical, mechanical, functional and proce­dural characteristics to activate, maintain, and deactivate physical connections for transmission;{2} Data-link handles channel addressing, data flow initialization, transmission control, error detection and correction--it provides the Network layer the capability to control switching;{3} Network handles end-to-end addressing, routing and switching;{4} Transport provides the transmission, the transfer, the reliable, controlled flow of data between Session entities;{5} Session handles name- to-address mapping, network monitoring, and literal management of the data exchange between Presentation entities;{6} Presentation has the specific purpose to represent information to communicat­ing entities in a way that preserves meaning while resolving syntax differences, providing encoding/decoding, encryption/decryption and the data formatting or format transla­tion necessary for file transfer;{7} Applications provides a number of services and procedures which are organized as 5 sub­layers: {a} applications, {b} DBMS, {c} file access, {d} end-user interaction, {e} end- user presentation.

OSI - Application Service: the upper three OSI layers provide the services to the application processes by ensuring that the infor­mation received is meaningful and processible.

OSI - Transportation service: the lower four OSI layers --the OSI "bit pipe"-- provide the functions that facilitate transparent transfer of information among distributed systems.  

OSPF - Open Shortest Path First; An Open Routing Protocol to send data over the shortest, least expensive path.

Packet: A unit of data to be routed from a source node to a destina­tion node in a communications network. A numbered segment of a data message. The group of bits including data and control ele­ments that is transmitted and switched as a whole. The data and control elements, and possibly error control information are arranged in a specified format according to the protocols used. Packet Switching: A data transmission process, utilizing addressed packets, whereby a channel is occupied only for the duration of transmission of the packet.

Packet Switching Data Network (PSDN): A set of equipment and inter­connecting links that provides a packet switching communications service to subscribers in the US.

PAD: Packet Assembler/Disassembler. The PAD assembles data into and out of packet format, and converts data between X.25 and other protocols.

PBX: Private Branch EXchange. A telephone switching device serving a specific user. A PBX is afacility-oriented product designed to provide connectivity over a single network, throughout an entire facility. Lines connect each telephone to the PBX, while trunks connect the PBX to the telephone company central office--the outside world. Any PBX can handle data through a modem; some newer digital PBXs handle data and digitized voice typically at 64KB.

PC Bus, XT Bus: The bus of the first IBM PC in 1981. 4.77 MHz, with 8-bit data and 20-bit address buses.

PDN: Public Data Network

PLL: Phase Lock Loop; PLL circuits constantly monitor their own output and use the feedback to fine-tune themselves

POP: (Carrier)  Point of Presence 

POS: Point of Sale; see VISA

POS: Programmable Option Select

POTS: Plain Old Telephone Service

PPP: Point to Point Protocol, an IP (Internet Protocol).

PRI: ISDN Primary Rate Interface; used to serve PBXs or other large capacity devices.

Protocol: An agreed set of rules governing the operation of a commu­nications link. In Telecommunications/Data Communications the word is used widely to mean any set of conventions governing use of the communication line itself and the format and control of the data being transmitted. Also called a line discipline or line procedure. There are three (3) kinds of protocols: 1} character oriented, 2} byte count oriented, and 3} bit oriented. {1} BISYNC (Binary Synchronous Protocol), IBM's character orient­ed protocol, uses special characters [STX/ETX--Start Text/End Text; STB/ETB--Start/End Text Block] to indicate start and end of Text Blocks of a message. {2} DDCMP (Digital Data Communication Message Protocol), DEC's byte count oriented protocol, uses a Header with a byte count to indicate how many characters (bytes) are in the following 'Data' portion of the message block.  {3} In bit oriented protocols, a special Flag character (flag byte) is used to separate the Header, Text, and Block-check parts of the message block. HDLC, ADCCP & CDCCP and X.25 are bit oriented, i.e., low level Data Link Control (DLC) protocols. See DLC, CCITT, OSI. 

PSN: Packet Switching Node

PSN: Packet Switched Network: Accunet, Datapac, Datcx-P, Telenet, Tymnet, and TRANSPAC.

PSPDN: Packet Switched Public Data Network

PTM: Packet Transfer Mode; what ARPAnet, Ethernet and Telnet do.

PTT: Postal Telegraph and Telephone. Government authority that typically operates the public telecommunications network, sets standards and policy, and negotiates communications internation­ally for a given country.

Queue: A line or list of items waiting for service; e.g., a message queue -- messages to be transmitted; a task queue -- tasks to be performed.

RBOC: Regional Bell Operating Company.

RIP: Routing Information Protocol; used in TCP/IP.

RISC: Reduced Instruction Set Computer. A CPU which has an instruc­tion set reduced to the bare minimum in order to increase proc­essing speed. Because of the simplicity of their design, RISC machines outperform CISC counterpart machines with conventional architecture, and are more cost-effective because fewer elements need to interact. See CISC.

Routers: A router supports 3 or more physical links, and must be compatible with OSI layers 1, 2, 3. For incoming packets, it decides which output link to use. "Switch" and "Packet Switch" are terms used with X.25 networks, rather than routers. Routing: The network function that determines the path along which data travels to its destination; i.e., the process of selecting the next node.

Routing Protocols: Routing Information Protocol[RIP]; used in TCP/IP. Routing Table Management Protocol [RTMP]; Interior Gateway Routing Protocol [IGRP]; Border Gateway Protocol [BGP]; Exterior Gateway Protocol [EGP]; OSPF - Open Shortest Path First; An Open Routing Protocol.

RPC: Remote Procedure Call.

RTIC: Real Time Interface Co-processor.

SAA: IBM's Systems Application Architecture. See DRDA.SCSI: Small Computer Systems Interface.

Server: A program on a LAN to provide multiple users access to a network resource. For example a file server.

SLIP: Serial Line Interface Protocol (RS232) - for long distance connectivity over telephone lines. Ade facto standard, SLIP defines a method for sending internet datagrams over anynchronous lines.

SMDS: Switched Multimegabit Data Services

SMTP: Simple Mail Transfer Protocol: allows users to send electron­ic mail over the network using standard mail commands.

SNA: (IBM's) Systems Network Architecture

SNMP: Simple Network Management Protocol, designed for management of multivendor, heterogeneous, TCP/IP based inter-nets and has found widespread acceptance as a de facto standard.

SONET: Synchronous Optical Network TSI (Time Slot Interchange) TDM addresses/slot assignments

SPARC: Scalable Processor ARChitecture. A computer processor archi­tecture based on a RISC design.

SQL: Structured Query Language; a query language to access databases, in particular relational data bases.

SS#7: Signaling System #7 - a new CCITT signaling protocol for digital networks: it meets present and future requirements for call control, remote control, management and maintenance func­tions and transfers signaling information without loss or dupli­cation.  PRI & SS7 use 24th DS0 as LAP D

STM: Synchronous Transfer Mode; what Telcos do with voice.

STP: Shielded Twisted Pair with DB9 interface

Stream: {1} Streams is a collection of system calls, kernel re­sources, and kernel utility routines that can create, use, and dismantle a "Stream". A Stream is a full-duplex processing and data transfer path betweeen a driver in kernel space and a proc­ess in user space. {2} A stream has three parts: aStream Head, zero (0) or moremodules, and aDriver or Stream End. The Stream Head provides the interface between the Stream and user process­es. Its principle function is to process streams related user calls. A module processes data that travel between the Stream Head and Stream End/Driver. A Streams Driver can be a device driver, providing the services of an external I/O device, or it can be an internal software driver, commonly called a pseudo- device driver. {3} Using a combination of system calls, kernel routines, and kernel utilities, STREAMS passes dataupstream between a driver and the Stream Head in the form of messages. Messages passeddownstream from the Stream Head to Stream End/Driver.

Sun SPARC: or Sun SPARCsystem; a family of workstation computers developed by Sun Microsystems. It has a 32 bit (15.8 MIPS) proc­essor, 8 Mb of main memory, expandable to 40 Mb; 64 Kb of cache memory and up to 4 Gb of mass memory. The Sun Operating System (SunOS) is UNIX based, integrated with MS-DOS which allows the user to switch between UNIX and DOS applications. The DOSWindows feature runs all mainstream DOS applications including several simultaneously.

switchSynchronous transmission: A mode of data transmission in which the transmitted signals are related to equal length, synchronized time frames.

T-0: Transmission circuit/service at DS0 rate; 64 Kb/s

T-1: Transmission circuit/service at DS1 rate; 1.544 Mb/s, see DS1 signaling. 24 DS0’s

T-2: Transmission circuit at DS2 rate; 6.312 Mb/s (4 t-1s) Not Used

T-3: Transmission circuit at DS3 rate; 44.736 Mb/s (28 T-1’s) See OC-1

T-4: Transmission circuit/service at DS4 rate; 274.176 Mb/s Not Used

TAT: Trans Atlantic Telecommunications; undersea cables both planned and in operation by CANUS, a Canadian US group.

TCAM: Telecommunications Access Method; an IBM software product to interface communication lines with applications software.

TCP: Transmission Control Protocol - supports connection, basic data transfer, data reliability, flow control, multiplexing, precedence and security functions.

TCP/IP: Transmission Control Protocol/Internet Protocol. One of several software protocols developed by the US DOD for intercon­necting nodes on a network. It was developed by the DARPA in the US DOD to promote interconnection of DOD networks in the early 1970s; it became a military standard in 1978. Progress within the OSI framework was not occurring fast enough so the DOD de­creed that only computer systems compatible with TCP/IP would be able to connect to the Defense Data Network (DDN). TCP a connec­tion oriented protocol with error correction often runs on IP, a connectionless datagram service.

TeleCom: TeleCommunications, the technology and term encompassing all transfer of information by electromagnetic means. This includes voice telephone, telegram, text or data transmission, facsimile, and digital or video image or picture transmission. In Voice communication, for person-to-person dialogue, lines with one pair of wires (Half-duplex/Two Wire) are normally adequate. Since a person cannot send and receive at the same time, each station is alternately sender and receiver; transmission is in one direction at a time, not both directions simultaneously. When the direction changes, the line is inverted. It is neces­sary, however, to have both sender and receiver connected at the same time so that the "message": the bidirectional conversation, can be transmitted. In Voice communications the "message" is the dialogue itself. In Data communication, each station can send and receive at the same time, but the "message" is only in one direc­tion. In order to transmit simultaneously in both directions it is necessary to use lines with two pairs of wires (Full- duplex/Four Wire ), one pair for each direction. However, in Data communications, the receiver does not have to be connected when the "message" is sent; the sender does not have to be present when the "message" is received. Because of this, "data messages" can be stored. The different needs for voice and message handling allow for two basic types of transmission serv­ice: a call service and a message service. The call service requires a two-way path, the message service requires a one-way transmission. The call service requires the activation of a path, a connection, between two stations or points to allow a conversa­tion. The connection may be fixed or switched point-to-point. No delayed or interrupted delivery is possible, hence no store and forward. The path is established for the entire conversation, this requires Circuit Switching: which includes 1} Space Divi­sion, 2} Frequency Division and 3} Time Division. Separate physical paths are required for Space Division, but not for multiplexing by Frequency Division or Time Division.{1} When the connecting links are physical, i.e., lines, the actual physical--metallic--switch points must be there to make the switch connections. These physical switch points are separated by space, hence the term Space Division. All electromechanical telephone switches are of this type. {2} Voice frequencies have a range of about 4000 Hertz--cycles per second; a transmission scheme that has a bandwidth with multiples of the voice range will allow many conversations to be sent over the same physical line. Each separate multiple is assigned as a channel; this use of frequency for channel separation is known as Frequency- Division Multiplexing (FDM).{3} For Time Division, all channels share the same frequencies, but they are separated on a time- sequential basis; the use of time for channel separation is known as Time-Division Multiplexing (TDM).  "Data messages" initial transmission can be delayed, they can be stored until a path becomes free. The entire path to the final destination need not be established for the entire conversation. Using Message Switching techniques the message can be forwarded to the next node and stored. Multiple messages may be forwarded to the connected node using TDM. Error detection and correction or retransmission insures complete and error free messages. Because data messages can also be subdivided into sequentially numbered "packets" of nominal size, their transmission can be handled quite differently than "messages". Using Packet Switching each "packet" can be sent by different, independent routing, or they may be broadcast to multiple nodes where they will be stored, and again forwarded or broadcast. The channel or circuit is dedicat­ed to the connection only for the duration of the packet's trans­mission. The complete message will be reassembled from the se­quential "packets" at the destination. If interrupted delivery is possible, receipt of "packets" of a low priority message may be interrupted by a higher priority message and later resumed.

TELNET: TELNET Protocol allows interfacing of terminals and termi­nal oriented processes.

TEMPEST: Terminal Electro-Magnetic Pulse Escape Safeguard Technique; the technique used to prevent certain electronic devices from emitting electro-magnetic pulses;
The Voice over Internet Protocol product designed by Franklin 800 Corp. in Westlake Village, CA 1n 1995.

10Base-T: TenBaseT; Type 10BASE-T is an Ethernet cable that uses an unshielded twisted-pair wire [10 Mb/s]. see Ethernet.

TLI: Transport Layer Interface; a UNIX programming interface to any transport layer provider that conforms to OSI concepts.

TOP: Technical and Office Protocol; developed by Boeing Corporation in 1985. TOP performs the same functions as MAP, except TOP is oriented to the movement of documents and files, while MAP (Manufacturing Automation Protocol, developed by General Motors Corporation) is concerned with control of robotic devices.  Both Protocols are OSI compatible.

Transaction: A logical unit of work; a collection or grouping of several related actions; an event.

TSI: Time Slot Interchange; TDM addresses/slot assignments

TSR: Terminate and Stay Resident; a software program usually in­voked through interrupts.

TurboMux: A high speed multiplexer channel that interleaves the transmission of many output data streams at the same time.

Two Wire: A 2-wire, half duplex circuit, permits communication in either direction but only one at a time. Full duplex requires a 4-wire circuit; i.e., two pairs of wires, one pair for each direction. See telecommunication.

UA: User Agent; the X.400 MHS function that allows a user to com­pose, send and receive messages. The other X.400 MHS function is the Message Transfer Agent.

UDP: User/Unreliable Datagram Protocol provides a connectionless, unreliable datagram delivery service which enables application programs to send messages to other programs using IP.

UNMA: Unified Network Management Architecture; AT&T's LAN Manage­ment software

UPS: Uninteruptible Power Supply; 1} On-line UPS provides both power conditioning as well as blackout protection; it maintains voltage within ± 3% of nominal. A dependable source of AC power is not a luxury; in fact, statistics indicate that power-line anomalies and failures could account for 30% of all data loss. 

  2} Standby UPS is a continuously charged battery which is acti­vated by line sensing devices when power fails; a switchover typically takes 10 milliseconds.

UTP: Unshielded Twisted Pair with RJ11 interface

VGA: Variable Graphics Array.

Virtual Circuit: An association between two nodes whereby the two nodes are able to interact as if a specific circuit were dedicat­ed to them throughout the transmission. When a virtual circuit is established, a logical connection is established, with the actual physical circuits being allocated according to route availability, overload conditions and other factors.

Virtual Machine: A computer designed to replicate (software) copies of its entire hardware-software interface in order to develop new software.

Virtual Memory: Two important concepts are 1} Address space and 2} Memory space: Address space is the set of all logical locations, for both instructions and data that can be used as an extension of the machine's own memory; Memory space is the set of actual, physical hardware locations available on the machine.  Program generated addresses are called virtual addresses because they refer to contiguous logical space, rather than physical memory. Pieces of a program, or its data, can be located anywhere in physical memory, i.e., in discontiguous physical blocks, but through the use of special registers is made to appear as if residing invirtually extended memory or memory that islogically contiguous.

  Computer memory, logical not physical; separate from a specific machine,

Virtual Terminal: A pseudo-device that connects a process to a physical terminal device. The virtual terminal can logically be disconnected from the physical terminal and be reconnected later.

VISA: An industry standard message format often used for POS trans­actions; a blocked, half-duplex, asynchronous protocol similar to IBM's Bisync (BSC).

VLIW: Very Large Instruction Word; a multiprocessor architechture design that facilitates execution of multiple, parallel opera­tions in a single clock cycle.

Voice Mail/Voice Messaging: A telephone service whereby a caller creates, addresses, and sends a personal (voice) message via a Touchtone telephone. The same message can be sent to many people simultaneously, removing the need for multiple calls. See IVR.

VRAM: Video Random Access Memory - much faster than standard RAM.

VT-100: The DEC Video Terminal 100 which had a major impact on the computer industry when introduced because it used convenient control codes for positioning the cursor, displaying text, etc., (ANSI screen controls). All recent VT-xxx DEC terminals are upwardly compatible with the original VT-100.  Most asynchronous terminals are compatible, and most PCs can emulate the VT-100 as well. See ANSI.

VPN: Virtual Private Network

VTAM: Virtual Terminal Access Method.

VTP: Virtual Terminal Protocol; software defined and hardware independent "universal" terminal protocol that provides terminal emulation capabilities between dissimilar end-systems.

WAN: Wide Area Network. A WAN provides for communication over broad geographic areas. A wide variety of communications media can be used: e.g., dedicated, leased and dial-up lines, microwave and satellite links. Nodes in a WAN can be connected by point-to- point lines or through packet switching networks.

WATS: Wide Area Telephone Service.

WOSA: Windows Open Services Architecture. It is debatable whether or not it is open, but it sure is Windows.

X.400: A CCITT Application Layer protocol. X.400 or MHS is a group of related recommendations that support electronic message ex­change (Email) over a variety of configurations.

XGA: EXtended Graphics Array; optimized for speed, high-resolution and upward compatible from the VGA, with up to 1024 x 768 pixels and 256 colors.

XPG: X/Open Portability Guide.

X Window System: A vendor-independent, network-transparent system for building windowing systems.