Glossary- T
A Data Communication Historical series
by  Bob Pollard

HOME                          INDEX

T1:

1) A category of leased telephone line service, allowing transfer rates of 1.5 Mbps (megabytes per second) over the Internet.  A T1 connection provides roughly 60 times more data than a normal residential 56K MODEM and is also extremely reliable.

2) Digital WAN carrier facility: T1 transmits DS-1-formatted data at 1.544 Mbps through the telephone-switching network, using AMI or B8ZS coding.

T-1:

A point-to-point digital communications circuit that carries 24, 64,000 bits per second channels: Each of which may be used for data or digitized voice. Digital Transmission Level 1 (1.544Mbps)

T2 Carrier

A specialized digital (AT&T) transmission system operating at a total speed of 6.312 million bits per second (Mbps) using Time Division Multiplexing (TDM): A T2 carrier can support up to 96 voice circuits.

T-3:

A category of leased telephone line service, allowing transfer rates of 44 Mbps (megabytes per second) over the Internet.

Digital WAN carrier facility: T3 transmits DS-3-formatted data at 44.736 Mbps through the telephone switching network.

T4 Carrier

A digital transmission system operating at 273 million bits per second (Mbps): A T4 carrier can support up to 4032 voice circuits.

T.30:

Describes the overall procedure for establishing and managing communication between two fax machines

T.38:

Defines procedures for real-time Group 3 facsimile communication over IP networks

T.120:

ITU standard that describes data conferencing: H.323 provides the capability to establish T.120 data sessions inside an existing H.323 session.

TA:

See Terminal Adapter.

TABLE DRIVEN:

A data communications process: Uses table lookup procedures in order to route messages in a network; or operate a MODEM; or provide data security access.

TABS:

Telemetry Asynchronous Block Serial: AT&T polled point-to-point or multipoint communication protocol that supports moderate data transfer rates over intra-office wire pairs.

TAC:

1) Terminal Access Controller: Equipment that allows a host computer to accept terminal connections, usually from dial-up lines.

2) Cisco Technical Assistance Center

T-CARRIER:

A series of digital transmission services established as specified by AT&T.

Time Division Multiplexing. Transmission speeds are 1.544 million bits per second or higher.

T-CONECTOR

A T-shaped co-axial cable connector: Allows devices to be attached to a single multi-drop conductor.

TAB:

Part of a dialog box that resembles a notebook or file divider: Provides navigation between different sections of information in the dialog box.

TACACS:

Terminal Access Controller Access Control System: Authentication protocol, developed by the DDN community, that provides remote access authentication and related services, such as event logging. User passwords are administered in a central database rather than in individual routers, providing an easily scalable network security solution.

TACACS+:

Terminal Access Controller Access Control System Plus: Proprietary Cisco enhancement to Terminal Access Controller Access Control System (TACACS); provides additional support for authentication, authorization, and accounting.

TAG:

Identification information, including a number plus other information

A tag is a basic element of the languages used to create web pages (HTML) and similar languages such as XML.

Another use of tags is related to reader-created tags where blog content (such as photos, music, etc.) may be ‘tagged’, which means a keyword, such as ‘politics’ or ‘gardening’ may be used. This enables searches for all the blog postings in the past week that are individually tagged.

TAG SWITCHING:

High-performance, packet-forwarding technology that integrates network Layer 3 routing and data link Layer 2 switching and provides scalable, high-speed switching in the network core. Tag switching is based on the concept of label swapping, in which packets or cells are assigned short, fixed-length labels that tell switching nodes how data should be forwarded.

TAGGED TRAFFIC:

ATM cells that have their CLP bit set to 1. If the network is congested, tagged traffic can be dropped to ensure the delivery of higher-priority traffic; sometimes called DE traffic

TAIL CIRCUIT:

The connection from a satellite or microwave receiver to a user's equipment

TAM:

See Telecommunications Access Method.

TANDEM DATA CIRCUIT:

A communication circuit: Passes through two or more serially connected data terminating devices.

TANDEM EXCHANGE:

A telephone switching center: Processes traffic between local exchanges.

TANDEM(ING) SWITCHING:

Dynamic switching of voice calls between VoFR, VoATM, or VoHDLC PVC(s) and sub-channels: Tandem switching often is encountered in multi-hop VoFR call connection paths.

TAP:

A connector attached to a cable that does not interfere with the existing signals in the cable; or where an attachment is made to a cable for the express purpose of monitoring the data in the cable.

TAPE RELAY:

A method of re-transmitting TTY message traffic from one channel (line) to another: Messages arriving on an incoming channel are normally recorded in the form of perforated tape. This tape is then read and the data transferred automatically, via the tape, into an outgoing channel, or manually transferred to an automatic transmitter for transmission on an outgoing channel.

TAPE SEARCH UNIT:

See TSU.

TAPE TRANSPORT:

A term generally used to describe a magnetic tape handler (drive) enclosed in a cabinet (housing) of some type. The device is usually equipped with the following: reels to wind and unwind the tape in either direction; heads (one per bit) designed to read and/or write on the tape in magnetic pulses; power units to operate the wind and rewind reels and to pass the tape through (over) the read-write heads; and electronic circuits to provide read-write capability. This term may also be used to describe a paper tape handler.

TAPI:

Telephony Application Programming Interface: A call control model developed by Microsoft and Intel.

TARGET TOKEN ROTATION TIME (TTRT):

1) The target time for the token to pass every Fiber Distributed data Interface (FDDI) node in the token path.

2) The value used by the Media Access Control (MAC) receiver to time the operations of the MAC layer.

TARIFF:

A schedule of regulations and rates for services provided by a common communications carrier

TARP:

TID Address Resolution Protocol: In OSS, a protocol that resolves a TL-1 TID to a CLNP address

TASI:

Time Assignment Speech Interpolation: A method of activating data communication channels via speech. Other application signals may be multiplexed on the same circuit when speech is not present.

TASK MANAGER:

A utility that provides information about programs and processes running on the computer: Using Task Manager, a user can end or run programs and end processes, and display a dynamic overview of the computers performance.

TASK TO TASK COMMUNICATION:

The process where one computer program exchanges data with another computer program

TASKBAR:

The bar that contains the Start button and appears by default at the bottom of the desktop: A user can click the taskbar buttons to switch between programs, hide the taskbar, move it to the sides or top of the desktop, and customize it in other ways.

TASKBAR BUTTON:

A button (description) that appears on the taskbar and corresponds (identifies) to a running application.

TAT:

Trans-Atlantic Telecommunications (cable): Originally: Trans-Atlantic Telephone (cable).

TAXI 4B/5B:

Transparent Asynchronous Transmitter/Receiver Interface 4-byte/5-byte: Encoding scheme used for FDDI LAN(s) as well as for ATM. Supports speeds of up to 100 Mbps over multimode fiber. TAXI is the chipset that generates 4B/5B encoding on multimode fiber.

TB:

Transparent Bridging: This feature supports connectivity for multiple VLAN(s) bridged between Dot1q interfaces and other interface encapsulations, or other types of interface media.

TBOS PROTOCOL:

Telemetry Byte Oriented Serial protocol: Protocol that transmits alarm, status, and control points between NE and OSS. TBOS defines one physical interface for direct connection between the telemetry equipment and the monitored equipment.

T-SPAN:

A transmission medium that supports a T-Carrier system

T-TAP:

A passive connection: Allows the extraction of signal data from a transmission line for testing, or other purposes. This process does not compromise the integrity of the data carried on the line.

TC:

1) Transmission Control: Transmission Control Characters.

2) Transfer Channel: Another name for a computer ‘port’

3) Technical Control: The total T C environment consisted of the necessary equipment to perform the following functions:

·         A cable connection (cross cut mainframe) facility for connecting outside lines (terminals) to the internal equipment interfaces.

·         Facilities for line and equipment testing and rerouting of failed lines and equipment.

·         MODEM and equipment racks for mounting the required MODEMs and equipment to interface the incoming and outgoing lines.

·         Secure Crypto interface facilities. The actual Crypto equipment is located in a high security area.

4) Telephony Controller: A new generic term for the Signaling Controller (SC) and the Virtual Switch Controller (VSC).

5) Transmission Convergence: Sub-layer of the ATM physical layer that transforms the flow of cells into a steady flow of bits for transmission over the physical medium. When transmitting, the TC sub-layer maps the cells into the frame format, generates the HEC, and sends idle cells when there is nothing to send. When receiving, the TC sub-layer delineates individual cells in the received bit stream and uses HEC to detect and correct errors.

TCA:

Telecommunications Access Method

TCAM:

See Telecommunications Access Method.

TCAP:

Transaction Capabilities Applications Part: SS7 protocol layer that helps exchange non-circuit-related data between applications

T-CARRIER:

TDM transmission; usually referring to a line or a cable carrying a DS-1 signal

TCC:

Terminating Call Control

T-CCS:

Transparent Common Channel Signaling: Feature that allows the connection of two PBX(s) with digital interfaces that use a proprietary or unsupported CCS protocol, without the need for interpretation of CCS signaling for call processing. T1/E1 traffic is transported transparently through the data network and the feature preserves proprietary signaling. From the PBX standpoint, this is accomplished through a point-to-point connection. Calls from the PBX(s) are not routed, but follow a preconfigured route to the destination.

TCCU:

Transfer Channel Control Unit: Control function equipment associated with the Transfer Channel (port).

TCL:

Toolkit Command Language: A Cisco IOS software scripting language used for gateway products both internally and externally.

TCL INTERFACE:

Tool Command Line Interface

Tcl/Tk:

Toolkit Command Language windowing Toolkit: A combination of a scripting language (Tcl) with a windowing toolkit (Tk). Used for rapid prototyping and application development.

TCP:

Transmission Control Protocol: An Internet protocol that provides full duplex host to host packet-switched computer communications networks standards.

TCP/IP:

Transmission Control Protocol / Internet Protocol: Networking protocols for communications across interconnected networks (including the Internet). The networks may incorporate diverse hardware architecture, computers and various operating systems. TCP/IP includes communication, connection and routing standard protocols. This protocol is the foundation of the Internet, and is an agreed upon set of rules directing computers on how to exchange information with each other. Other Internet protocols, such as FTP, Gopher and HTTP sit on top of TCP/IP.

TCM:

See Time Compression Multiplexer.

TCU:

1) Trunk Coupling Unit: In Token Ring networks, a physical device that enables a station to connect to the trunk cable.

2) Teletypewriter Control Unit: A device that controls and coordinates operations between teletypewriters and message switching (ASC) centers.

3) See Terminal Control Unit.

TD:

1) Transmitter-Distributor: Teletype equipment consisting of a paper tape reader and transmitter/line signaling control device. The reader interprets (senses) the tape punched holes and the transmitter- distributor converts the hole sensing to electrical impulses for transmission on the line.

2) Transmit Data: The RS 232 data signal sent on pin 2 from a DTE device to a DCE device.

TDM:

Time-Division Multiplex (multiplexing): The time-sharing of a transmission facility or network by a number of users.

Information from multiple channels can be allocated bandwidth on a single wire (channel) based on pre-assigned time slots. Bandwidth is allocated to each channel regardless of whether the station has data to transmit

TDM CROSS-CONNECT:

Allows DSO channels from one T1 or E1 facility to be cross-connected digitally to DS0 channels on another T1 or E1: By using this method, channel traffic is sent between a PBX and CO PSTN switch or other telephony device, so that some PBX channels are directed for long-distance service through the PSTN while the router compresses others for interoffice VoIP calls.

TDMA:

Type of multiplexing where two or more channels of information are transmitted over the same link by allocating a different time interval (slot / slice) for the transmission of each channel: Some form periodic synchronizing signal or distinguishing identifier usually is required so that the receiver can differentiate between individual channels.

See Time Division Multiple Access.

TDR:

Time Domain Reflectometer: Device capable of sending signals through a network medium to check cable continuity and other attributes. TDR(s) are used to find physical layer network problems.

TDX:

See Time Division Multiplexer.

TE:

Terminal Equipment: Any ISDN-compatible device that can be attached to the network, such as a telephone, a fax, or a computer.

TECHNICAL ARCHITECTURE:

A structure that summarizes the mixture of hardware, software, and communications facilities: supports or will support the business systems and other parts of the information environment within an organization.

TECHNICAL CONTROL (TECH CONTROL):

See TC

TEI:

Terminal Endpoint Identifier: Field in the LAPD address that identifies a device on an ISDN interface.

TELCO:

Telephone Company

TELCO-RETURN CM:

A cable MODEM that uses the cable plant only for subscriber downstream traffic and uses the PSTN for subscriber upstream traffic: This may be necessary in older cable plants.

TELECOMMUNICATIONS:

The transmission of voice and/or data through a medium by means of electrical impulses: includes all aspects of transmitting information.

TELECOMMUNICATIONS ACCESS METHOD (TAM):

The software that allows remote devices to transfer data to and receive data from host processors

TELECOMMUNICATIONS INDUSTRY ASSOCIATION (TIA):

A membership organization concerned with various standards in the telecommunications industry.

TELECOMMUNTING:

Refers to a process where computer (or terminal) based work is accomplished at an employees home on a device which is connected via a communications channel to a processing device at the employers office.

TELECONFERENCING:

A conference between remote stations linked by a telecommunications medium

TELECOPIER:

A facsimile (FAX) machine

TELEGRAM:

Written matter intended to be transmitted by telegraphy (TTY) for delivery to the addressee. This term also includes radio-telegrams unless otherwise specified. This definition of the term telegraphy has the same general meaning as defined in the ‘1979 General Worldwide Administrative Radio Conference’ Convention.

TELEGRAPH:

A system employing a timed interruption, or change in the polarity of DC current signaling, to convey coded information.

TELEGRAPH CONCENTRATOR:

An automatic or manual switching arrangement where a number lines or terminals may be connected to a lesser number of trunks or main lines, a sharing function.

TELEGRAPHY:

A Telegraph device or system used for transmitting or receiving information (data), normally digital information and low speed devices.

TELEMEDICINE:

The provision for health care services to obtain or report information from a remote site, utilizing network supporting audio, video and computer data transmissions.

TELEMETRY:

The transmission and/or collection of data obtained by sensing conditions on a communications media, in a real time environment.

TELENET:

A commercial services network providing both packet switching and circuit switching services

TELEPAC

Refers to a packet switched network implemented in Switzerland and/or in Portugal.

TELEPHONY:

A term initially used to describe voice telecommunications, but now used to describe voice/data/video communications.

TELEPHONY API (TAPI)

Application Programming Interface (API): Used by communications programs to work with telephony and network services. Communications programs, such as, HyperTerminal and Phone Dialer use TAPI to dial, answer, and route telephone calls on conventional telephony devices, including PBXs, modems, and fax machines. TAPI 3.0 also provides Internet Protocol (IP) telephony support, which Phone Dialer and other programs use to transmit, route, and control real-time audio and video signals over IP-based networks such as the Internet.

TELEPRINTER:

Other designations: Teletype and Teletypewriter - A term used to describe various types of terminals consisting of both keyboard and printer but no CRT

TELEPROCESSING:

A word (term) used by IBM to describe remote locations (terminals, etc.) that are connected to a central processor in order to perform RJE (Remote Job Entry) functions, usually connected by telephone lines. A Western Union Division also used the Teleprocessing name, see TII.

TELE-ROUTER:

An optional software overlay product for the Cisco VCO/4K switch. Tele-Router uses its own database to locate dialed digit strings from inbound calls and routes calls based on this information.

TELETEX:

A higher speed ASCII based text transmission service designed to replace Telex.

TELETEXT:

One way transmission for public distribution of graphics and text

TELETYPE / TELETYPE CORPORATION:

A trademark (and manufacturer) for a series of different types of teletypewriter equipment designed for data communications systems.

TELETYPEWRITER (Teletype):

A Send and/or Receiving communications device similar to a standard electric typewriter usually associated with a paper tape reader. Most of these units are of the ASR (Automatic Send and Receive) type of equipment, which consisted of a console and transmitting and receiving units. The transmitting unit was usually a paper tape transmitter. In many cases line and protocol control devices are provided. The communications code is usually the Baudot (modified) or ASCII code set.

TELETYPEWRITER EXCHANGE ‘Service’ (TWX):

See TWX

TELEX SERVICE:

See TELEX®

TELEX®:

A communication service involving teletypewriters connected through automatic exchanges.

A data communications service using dial-up lines and Baudot code allowing customers to communicate temporarily and directly. The system uses asynchronous apparatus and the circuits of the public telegraph network, world wide. Computers may be connected to the Telex network.

TELEX SERVICE:

See TELEX®

TELNET:

1) A protocol used for logging onto remote computers from anywhere on the Internet.

Telnet is an application that allows logging into a Unix computer. A drawback of Telnet is that it's character-based, and requires the use of the Unix language in order to communicate.

2) A terminal emulation protocol that is widely used on the Internet to log on to network computers: Telnet also refers to the application that uses the Telnet protocol for users who log on from remote locations.

TELNET REMOTE LOGIN PROTOCOL:

A virtual terminal service defined by the Telnet Network and implemented by most versions of Unix; also specified by the Department of Defense (DoD).

TELPAK:

A type of communications link provided by a common carrier: It represents a band of frequencies, which can be subdivided into voice and/or data channels of various bandwidths.

TEMPLATE:

Certain applications use template files to pre-load default configurations settings. Microsoft Word uses a template called NORMAL.DOT to store information about page setup, margins and other document information.

TEMPORARY TEXT DELAY (TTD):

A transmission control character used in IBM's Binary Synchronous Communications Protocol to signify a delay in the transmission of text, within an overall message.

10base2:

The Ethernet and IEEE 802.3 standard for base-band Local Area Networks (LAN) using a coaxial cable up to 200 meters long and carrying data at 10 megabits per second (Mbps). Cables connect to network adapters through a BNC connector.

10baseT:

The Ethernet standard for Local Area Networks (LAN) using twisted pair cable carrying data at 10 megabits per second (Mbps).

TE1:

See Terminal Equipment Type 1.

TERABYTE:

TB, a trillion bytes

TERENA:

Trans-European Research and Education Networking Association: Organization that promotes information and telecommunications technologies development in Europe

TERMID:

SNA cluster controller identification for switched lines only.

TERMINAL:

An outstation: Consisting of a remote send/receive device or unit. The Terminal could consist of another computer, an ASR, a Compound Terminal or any other special device; simple device where data can be entered or retrieved from a network.

TERMINAL ADAPTER:

A terminal adapter handles data digitally and therefore does not need a MODEM to modulate or demodulate an analog signal. Terminal adapters can be an internal board or an external box that connects to the computer through the serial port. An interfacing device used in an ISDN environment. Device used to connect ISDN BRI connections to existing interfaces, such as EIA/TIA-232; essentially, an ISDN MODEM.

TERMINAL ADDRESS:

An identifying character(s) used to direct a message to a specific terminal (system) within a group of interconnected terminals (system).

TERMINAL CONTROL UNIT (TCU) / TERMINAL CONTROLLER:

A device used to connect and control a local group of terminals or a single terminal control unit that provides for terminal selection and protocol functions. See DTE

TERMINAL EMULATION:

A hardware/software process where a device is made to ‘appear’ and ‘perform like’ a specific terminal device: This process is a common technique utilized for connection between a PC and a mainframe (or minicomputer).

Network application in which a computer runs software that makes it appear to a remote host as a directly attached terminal

TERMINAL EQUIPMENT TYPE 1 (TE1):

In an Integrated Service Digital Network (SDN): A type of terminal equipment directly compatible with the ISDN network.

TERMINAL EQUIPMENT TYPE 2 (TE2):

In an Integrated Service Digital Network (ISDN): A type of terminal, which must be connected to the ISDN network via a specially designated point, normally an RS 232 or RS 449 interface.

TERMINAL IN SERVICE:

RS-449 (Pin 28): A signal that indicates the Data Terminal Equipment (DTE) is operational.

TERMINAL INTERFACE PROCESSOR (TIP):

A device used to interface equipment to a specifically defined network. A term used by ARPAnet and TELENET.

TERMINAL NODE:

Refers to an IBM System Network Architecture (SNA) network device, which is not user programmable.

TERMINAL POLLING:

The process of asking each terminal, in sequence, if they wish to transmit (poll) or are ready to receive (call). An electrical, mechanical or control character action. The communications device or computer queries each terminal by transmitting a message (control characters) that the terminal can acknowledge by indicating its need for service. If a negative response to the polling is received from a terminal the polling continues with the next terminal in sequence until all terminals on the polling list are queried. Normally only one terminal at a time can be active, sending or receiving.

TERMINAL SERVER:

A control device (server) used to connect sets of terminals to a Local Area Network (LAN) or other network. The terminal server does the work of answering the calls and passes the connections on to the appropriate terminal (node). Terminal servers provide the inter-network intelligence that is not available in the connected devices

TERMINAL TIMING:

See Transmit Signal Timing

TERMINATED LINE:

A communications line terminated through a resistance equal to the line impedance to eliminate reflections (interference).

TERMINATION:

An end item (equipment) that is connected to a circuit (line): An impedance media connected to the end of a circuit being tested. The points on a switching network to which a trunk or line may be attached.

TERMINATOR:

A device needed to terminate a linear bus; it marks the beginning and end of the cable.

TERRESTRIAL:

A general term applied to land based long distance transmission facilities, non-satellite.

TESS:

The Exponential Encryption System: A system of separate but cooperating cryptographic mechanisms and functions for the secure authenticated exchange of cryptographic keys, the generation of digital signatures, and the distribution of public keys. TESS employs asymmetric cryptography, based on discrete exponentiation, and a structure of self-certified public keys.

TEST BOARD:

See TC

TEST CENTER:

A facility designed to provide access to all network or system facilities and/or components for test purposes.

TEST MODE:

RS-449 (Pin 18): A signal indicating the DCE (Data Communication Equipment) is in a test mode and can’t send data.

TE2:

See Terminal Equipment Type 2.

TEX:

See TELEX®

TEXT:

The information portion of a message: Usually does not include the header (address), check characters, start of message and end of message characters.

TEXT EDITOR:

A program designed to produce documents from a users computer terminal, and offers capabilities including:

1) ‘Cut and Paste’ capabilities

2) Renumbering and indexing of text items.

3) Multiple terminal support/timesharing monitor to supervise the sharing of programs among users while guaranteeing file integrity

TEXT SERVICE:

A program that enables a user to enter or edit text: Text services include keyboard layouts, handwriting and speech recognition programs, and Input Method Editors (IME). IME(s) are used to enter East Asian language characters with a keyboard.

TFN:

Tribe Flood Network: A common type of Denial-of-Service (DoS) attack that can take advantage of forged or rapidly changing source IP addresses to allow attackers to thwart efforts to locate or filter the attacks.

TFS:

Technical Facilities System (replaced EDITS): An analysis and trouble reporting system.

TFTP:

Trivial File Transfer Protocol: Simplified version of FTP that allows files to be transferred from one computer to another over a network, usually without the use of client authentication (username and password).

TGT:

Ticket Granting Ticket: A credential that the key distribution center (KDC) issues to authenticated users

TGW:

Trunking Gateway:. A gateway that supports only bearer traffic, no signaling traffic: For example, a gateway that terminates T1s (or greater) with no signaling control is a trunking gateway.

TH:

Transmission Header: SNA header that is appended to the SNA Basic Information Unit (BIU). The TH uses one of a number of available SNA header formats.

THE-NET:

Texas Higher Education Network: Regional network comprising over 60 academic and research institutions in the Texas, U. S. area.

THERMAL NOISE:

A form of electromagnetic noise: Sometimes referred to as Gaussian noise, that occurs in an electronic circuit and is proportional to ambient temperature.

THICK WIRE:

An often used term for describing the standard (50 ohm) Ethernet/IEEE 802.3 cable

THIN ETHERNET / THINNET:

Sometimes known as ‘Cheaper-net’: Thin Ethernet is a phrase used in LAN (Local Area Network) environments to describe a cost saving measure where Personal Computers would be linked together using a narrower diameter coaxial cable, operating at the same frequency as Ethernet, but at shorter distances.

THIN WIRE:

An often-used term for describing the 75 ohm co-axial cable used in some Ethernet installations.

3G (Third Generation Wireless):

The next generation of wireless communications beyond today's digital PCS (Personal Communication Services) technologies: When available, 3G wireless technologies will allow for much higher transmission rates to wireless devices.

THEORETICAL MIDPOINT (TMP):

The theoretical point that divides an international private line circuit into its respective US and foreign halves. A US carrier is responsible for the US portion and a foreign carrier assumes responsibility for the foreign half.

THRASHING:

The collapse of processing efficiency when over-commitment of main memory is attempted allowing no useful work to be accomplished. Typically, thrashing can be caused by:

1) The total active tasks exceeding available memory.

2) Space is acquired for some active tasks by taking space allocated to other active tasks.

THREAD COUNT:

In Task Manager, the number of threads running in a process

THREAD / THREAD DRIFT:

A series of messages with the same subject: It consists of an original message and all the replies and replies to replies that follow. Sometimes the replies will stray from the original subject, and this is called 'thread drift'.

THREE-WAY HANDSHAKE:

Process where two protocol entities synchronize during connection establishment

THREE VECTOR FONTS:

These are Modern, Roman, and Script fonts.

THRESHOLD:

Each PM parameter has a provision-able threshold that defines the autonomous message trigger point. Thresholds usually are defined in terms of either a specific BER value or a specific number of events counted during a set time period.

THROUGHPUT:

A measure of the productivity of a computer, network, or device:

1) In a Front End Computer throughput may be expressed in bandwidth or the number on various speed lines that can be connected and serviced simultaneously (total sum of bits, words, etc.)

2) The average rate at which jobs are completed by the system in an interval of time or the rate at which information is communicated during a specified time period. Throughput is frequently used as a figure of merit for a system, so that the higher the throughput, the more highly regarded the system is, but some factors must also be considered or throughput will be deceptive. The capacity of the system, the time interval over which the throughput is measured, the load on the system, and the job mix all act as factors that have an affect on system/ data communications throughput.

THROUGHPUT DELAY:

The amount of time needed to accept data input and transmit it as output.

THUMBNAIL:

A miniature version of an image that is often used for quick browsing through multiple images

TI:

Transmission Identifier: A line of protocol information that is transmitted ahead of each message on all asynchronous, and some synchronous, lines. Previously used in a discontinued message switching system.

TIA: Telecommunications Industry Association: Refer to EIA/TIA

TIC:

Token Ring Interface Coupler: Controller through which a FEP connects to a Token Ring

TID:

1) Tunnel Identifier: Used to identify a GTP tunnel between two GSN(s) in a GPRS network: Contains a MM Context ID and a NSAPI. A tunnel is created whenever a SGSN sends a Create PDP Context Request in a GPRS network.

2) Terminal Identifier

TIE LINE:

A dedicated or private line leased from a telephone company for the use by a subscriber, which is not part of the public switched network.

A connection that emulates a temporary tie-line trunk to a private branch exchange (PBX). A tie-line connection is set up automatically for each call and is torn down when the call ends.

TIER 1 AUTHENICATION:

Call authentication using DNIS and CLID

TIER 2 AUTHENICATION:

User authentication using User ID and Password

TII:

Teleprocessing Industries Incorporated: A systems and software group; part of the Western Union Corporation.

TIME BOMB:

Usually refers to a malicious action triggered at a specific date or time.

TIME COMPRESSION MULTIPLEXER (TCM):
A Multiplexing device that uses Time compression techniques rather than time division: TCM allows high-speed transmission over local loop facilities.

TIME DIVISION:

Refers to interleaving (interspersing) several message, characters or bits, which are separated from each other in time on a single transmission channel. See Concentrator.

TIME DIVISION MULTIPLE ACCESS (TDMA):

1) A satellite communication function where multiple earth stations have ‘time slot’ accesses to the full transponder bandwidth for short periods.

2) A digital communication technology used by some carriers to provide PCS (Personal Communication Services) and cell phone services: Other technologies used are CDMA (Code Division Multiple Access) and GSM (Global Standard for Mobile).

TIME DIVISION MULTIPLEXER (TDM/TDX):

A device that allows more than one slow speed device to share a common high speed line. The line time is divided into time slots and each slow speed device is assigned a time slot. The time slots may vary in the time allotted (multiple slots) due to different device speeds.

TIME-OUT:

A timing control function where a process is discontinued if an expected event does not occur within a predefined period of time.

Event that occurs when one network device expects to hear from another network device within a specified period of time, but does not: The resulting timeout usually results in a retransmission of information or the dissolving of the session between the two devices.

TIME SERVER:

A computer that periodically synchronizes the time on all computers within a network: This ensures that the time used by network services and local functions remains accurate.

TIME SHARING:

A method of operation (processing) in which a computer facility is shared concurrently by several users for various purposes: The computer could be handling requests serially or in a multiprocessing mode, but because of the computer speed the user, usually, would be unaware of the processing mode. Or the term could refer to the sharing of a communication channel (line).

TIME SLOT:

A term used in a LAN (Local Area Network) environment to describe a sequence position or assigned time period.

TIME STAMP:

A certification by a trusted third party specifying that a particular message existed at a specific time and date: In a digital context, trusted third parties generate a trusted time stamp for a given message by having a time stamping service append a time value to a message and then digitally signing the result; the time of creation or last modification recorded on a file or another object. Users can usually find the timestamp in the Properties section of a file.

TIME TO LIVE:

A function control field: Used in the Transmission Control Protocol / Internet Protocol (TCP/IP) transmission package to limit the amount of time that a package might exist in a network. This timer is used to eliminate package looping.

TIMED RELEASE CIRCUIT:

A type of circuit designed to automatically release other connected circuits after a preset interval.

TIMED TOKEN PROTOCOL:

Basic rules defining how the Target Token Rotation Time (TTRT) is set, the length of time a station can hold the token, and how the ring is initialized.

TIMING:

The setting and observance of the elapsed time of an action or data communications process, often the function of a MODEM.

TIMING SLIP:

A sudden data transmission timing delay (change) during high-speed digital transmission: Often caused by the use of different T1 carrier suppliers.

TINA-C:

Telecommunications Information Networking Architecture Services: Applications corresponding to TINA guidelines.

TIOS:

Trans-path Input Output Subsystem

TIP AND RING:

1) Designation for the parts of a plug that is inserted into a socket: A plug would be located on each end of a patch cord. Patch cords are used in facilities where rerouting and maintenance is performed, such a Technical Control facility.

2) Pair of wires that provide the electrical connection between a telephone set and the local CO. The positive side of a POTS (Plain Old Telephone Service) telephone line is the tip. It is designated internationally as black, but in the U.S. it often is designated green. The ring, negative side, which is designated red internationally and in the U.S. When tip and ring are terminated on a connecting block, tip usually goes on top (left) and ring usually goes on the bottom (right).

TIP:

See Terminal Interface Processor.

TIRKS:

Trunk Information Record Keeping System: Bellcore OSS that provides record keeping for interoffice trunk facilities.

TITLE BAR:

The horizontal bar at the top of a window that contains the name of the window: On many windows, the title bar also contains the program icon, the Maximize, Minimize, and Close buttons, and the ‘?’ button for context Help. To display a menu with commands such as Restore and Move, right-click the title bar.

TLA:

Three Letter Acronym

TLAP:

Token-Talk Link Access Protocol: Link-access protocol used in a Token-Talk network. TLAP is built on top of the standard Token Ring data-link layer.

TLD:

Top Level Domain: The last (right-hand) part of a complete Domain Name. For example in the domain name www.mumbo.net, ‘net’ is the Top Level Domain. There are a large number of individual TLD, for example: .biz, .com, .edu, .gov, .info, .int, .mil, .net, .org,

TL-1:

Transaction Language One: Bellcore term for intelligent network elements.

TLS:

Transport Layer Security: An IETF protocol designed to replace SSL.

TM:

Traffic Management

TMN:

Telecommunication Management Network: ITU-T generic model for transporting and processing OAM&P information for a telecommunications network.

TMP:

See Theoretical Midpoint

TMSI:

Wireless-Temporary Mobile Subscriber Identity: A temporary code used to identify a MS, which is assigned using encryption after the MS is identified to the HLR.

TN:
Telephone Number

TNC:

Threaded-Neill-Concelman: A type of miniature coaxial cable connector using a threaded connector instead of a bayonet lock.

T9® TEXT INPUT:

A feature built into many phones where one key press per letter is used when entering text on a wireless phone. T9 helps make entering text on a limited keypad quick and easy.

T-NOTIFY:

Time Notify: Specifies how often SMT initiates neighbor notification broadcasts.

TN3270:

Terminal emulation software that allows a terminal to appear to an IBM host as a 3278 Model 2 terminal

TOGGLEKEYS:

A feature that sets the keyboard to beep when one of the locking keys (CAPS LOCK, NUM LOCK, or SCROLL LOCK) is turned on or off.

TOKEN:

A unique frame that is passed continuously around a local area network (LAN): As it passes, the token gives the workstation the ‘all clear’ to transmit data. The frame normally consists of a set of bits, which define the start of the frame, a set of control bits and a set of bits to define the end of the frame.

TOKEN BUCKET:

A formal definition of a rate of transfer: A token bucket has three components: a burst size, a mean rate, and a time interval (Tc). A token bucket is used to manage a device that regulates data flow.

TOKEN BUS:

A Local Area Network (LAN) access mechanism: All stations attached to the bus check for a broadcast token. Stations requesting to transmit must receive the token before transmitting.

TOKEN HOLDING TIMER:

A timer that controls the amount of time a station may hold the token in order to transmit asynchronous frames. Or the elapsed time during which a device may transmit after it has received the access control token.

TOKEN PASSING:

A network access method: Uses a distinctive character sequence as a symbol (token). The token is passed from node to node indicating when to begin transmission. Any node can remove the token, begin transmission, and replace the token when it is finished.

TOKEN RING:

1) Local Area Network (LAN) architecture: Connects stations in a closed loop and grants permission to send by circulating a token that users may acquire and replace with a message. As defined in the Institute of Electrical and Electronic Engineers (IEEE) 802.5, in Ring architecture, a special data packet, called a token, is passed continuously from node to node. The sequence of nodes is governed by the physical order in which the nodes appear on the ring. Every node on the ring may see the data, but only the addressed receiving node will accept it.

2) Token-passing LAN developed and supported by IBM. Token Ring runs at 4 or 16 Mbps over a ring topology.

TOKEN RING CARD:

The circuit board that is inserted into a computer device that will allow a connection to a token-ring Local Area Network (LAN); usually, one token-ring card on the network is the token monitor. The sending of messages between token-ring cards can be used to gather information about network activities.

TOKEN RING EXTENDED USER INTERFACE (TOKREUI):

A direct interface to the link protocol control of the IBM Token Ring Network: Some token ring software products use TOKREUI and some competitive local area networks (LANs) provide TOKREUI compatibility.

TOKEN RING TOPOLOGY:

See Token ring

TOKEN ROTATION TIMER (TRT):

In Fiber Distributed Data Interface (FDDI) network: TRT is a timing clock that monitors the time period between receipts of tokens.

TOKEN STORAGE KEY:

Cryptography key used to protect data that is stored on a security token

TOKEN TALK:

Apple Computer's data-link product that allows an AppleTalk network to be connected by Token Ring cables

TOKEN TREE LAN:

A type of local area network where the designed topology is in the form of branches interconnected via active hubs. The active hubs, using a token passing scheme, grant a node access to the network.

TOKREUI:

See Token Ring Extended User Interface

TOLL CENTER:

A Class 4 central office: Terminates message circuits and channels.

TOM:

Top of Memory: A design limit at the 640kb mark on most Personal Computers (PC). Often the boot record does not completely reach top of memory, thus leaving empty space. Boot sector infectors often try to conceal themselves by hiding around the top of memory. Checking the top of memory value for changes can help detect a virus, though there is also non-viral reasons this value change.

T-1 TIMER:

A term used in packet-switched network environments to measure the interval of timeouts during data exchanges and link initialization.

TOOLBAR:

In a program in a graphical user interface, a row, column, or block of on-screen buttons or icons: When clicked, these buttons or icons activate certain functions, or tasks, of the program. For example: the toolbar in Microsoft Word contains buttons for changing text to italic or boldface, and for saving or opening a document. Users can often customize toolbars and move them around on the screen.

TOPOLOGY:

The physical arrangement of network nodes and links: Examples: ring, star, and bus.

TOPS:

Refers to the operating system used by the Digital's 10's and 20's.

TOP LEVEL DOMAIN:

See TLD

TORN TAPE MESSAGE SWITCHING SYSTEM:

In a manual ‘Torn Tape’ data communications switching center all messages received at the center were via a paper tape perforator, which created a punched paper tape based on the message content. All transmitted messages (from the center) were via a paper tape transmitter. Each connected tributary required an assigned perforator and/or transmitter position. When a complete message was received at the center the message would be torn off the perforator, hence the name ‘torn tape’. The message (tape) would then be hand carried, when necessary, to the appropriate tape transmitter for transmission to the receiving tributary.

ToS:

Type of Service / Terms of Service or The Other Service, a term often used among a group of people who have switched from one on-line service to different on-line service

TOUCH TONE:

AT&T proprietary trademark for push-button DTMF (Dual Tone Multi-Frequency) telephone dialing

 TP:

Termination Point: Example: Among other definitions, a termination point is a transmission line or path that terminates or originates on a NE, such as the Line Card unit on the Cisco ONS 15900

TP 1 through 5:

The various services level of the International Standards Organization (ISO), IS - 8073 Transport Layer Protocol.

TP0:

Transport Protocol Class 0: OSI connectionless transport protocol for use over reliable sub-networks; defined by ISO 8073.

TP4:

Transport Protocol Class 4: OSI connection-based transport protocol; defined by ISO 8073.

TPD:

Mechanism used by some ATM switches that allows the remaining cells supporting an AAL5 frame to be discarded when one or more cells of that AAL5 frame are dropped. This avoids sending partial AAL5 frames through the ATM network when they have to be retransmitted by the sender.

TPDU:

See Transport Protocol Data Unit.

TPPMD:

Twisted-Pair Physical Medium Dependent

TPTB:

The Powers That Be: Refers to the management of the activity being discussed.

TRACEROUTE:

An Internet utility that traces and provides information concerning the connection path (route) from the client machine to the remote host being contacted: It reports the IP addresses of all the routers in between.

TRACKS:

The longitudinal division of magnetic tape, drums and discs where information is stored. The tracks are divided into segmented parts.

TRAFFIC:

Another term for message transmission, reception or storage

TRAFFIC ENGINEERING:

The science of communications facility and data flow design and optimization, which results in maximum availability of facilities and efficiency of operation.

TRAFFIC FLOW ANALYSIS:

A data flow analysis and design process for a network or system in order to ensure that proper communication lines and equipment will be installed. Or this task could be accomplished for the improvement of an existing system.

TRAFFIC MANAGEMENT:

The process of managing the data (traffic) flow within a network

TRAFFIC SERVICE POSITION SYSTEM (TSPS):

A toll switchboard position configured as a push button console.

TRAILER OR TRACE BLOCK:

A block (group of characters or bits) of control information which may be transmitted at the beginning or end of a message and is used to trace errors and missing blocks (information).

TRAINING:

1) Excluding personal training, the process where a receiving MODEM achieves equalization (synchronization) with the transmitting MODEM.

2)The process of teaching the speech recognition engine to recognize a user’s voice and manner of speaking: The speech engine looks for patterns in the way a person speaks, enabling it to provide better accuracy when dictating text. A person trains the engine by reading text in the training wizard mode, and continues to train the engine as text is dictated during the normal working phase.

TRAINING PATTERN:

The transmission of a training signal sequence: See Training

TRAINING TIME:

‘Learning time’: Training time refers to the time it takes a MODEM equalizer to achieve equalization (synchronization).

TRANSACTION / TRANSACTION PROCESSING:

1) The processing of individual items of data or tasks, known as transactions: This would normally be accomplished in a real time environment without any sorting or editing. In a batch processing or remote job entry environment, the transaction is also known as a job or job step.

2) For Message Queuing: the pairing of two or more actions that are performed together as a single action; the action succeeds or fails as a whole. Using Microsoft Distributed Transaction Coordinator (MS DTC) ensures that either both actions succeed or neither is executed.

TRANSACTION SERVICES LAYER:

Layer 7 in the SNA architectural model: Represents user application functions, such as spreadsheets, word-processing, or e-mail, through which users interact with the network.

TRANACTIONAL MESSAGE:

For Message Queuing, a message that can be sent and received only from within a transaction: This type of message returns to its prior state when a transaction is terminated abruptly. A transactional message is removed from a queue only when the transaction is completed; otherwise, it remains in the queue and can be subsequently read during another transaction.

TRANSACTION DEAD LETTER QUEUE:

For Message Queuing, a queue that stores transactional messages that cannot reach their destination queue. Transaction dead-letter queues store failed messages on the computer on which the message expired. Messages in these queues are written to disk and are therefore recoverable.

TRANSCEIVER:

A device capable of transmitting and receiving simultaneously

TRANSDUCER:

An intermediate device that converts the physical (electrical) properties of a signal from one form to another: Example: The interface between a computer (electron based signals) and a fiber optic cable system (photon based signals). Also used in satellite communications.

TRANSFER CHANNEL:

Input/Output computer-device interface (port). A data transfer connection between the computer and an associated device.

TRANSIENTS:

Short duration transmission or signal interruptions

TRANSISTER:

The transistor can be found in nearly every common electronic device manufactured today. Originally created in the late 1940s by Bell Labs, the transistor was hailed as a smaller, less-expensive, and cooler-running replacement for the vacuum tube. Today, millions of transistors are often packed into silicon chips to create the processors used in modern computers.

TRANSIT SPAM:

A form of e-mail spam which is sent through a different Internet mail server than the one it originates from, usually with forged headers to make it look as if it came from the original site.

TRANSIT TIMING:

A delay timer used to eliminate looping between nodes. Used in the network layer of some packet switched systems.

TRANSLATION:

In data communication it involves the conversion of one code set to a second code set on a character-by-character basis. See Translator

TRANSLATION PROGRAM:

Refers to a program capable of analyzing high-level and assembly language instructions and then substituting (converting to) the machine language version. ‘Assembly Program’ used for assembling program segments and preparation of programming systems.

TRANSLATOR:

1) Data communication and telephony, a translator converts the digits dialed to information required for call routing.

2) A hardware device to convert information from one system of representation to another system of representation, without destroying the intended message or content.

3) Computer software that converts non-uniform information from one system into equivalent information in another system. See Translation or Translation Program

TRANSMISSION CONTROL LAYER:

Layer 4 in the SNA architectural model: This layer is responsible for establishing, maintaining, and terminating SNA sessions, sequencing data messages, and controlling session level flow.

TRANSMISSION CONTROL PROTOCOL / INTERNET PROTOCOL (TCP/IP):

A set of networking protocols widely used on the Internet that provides communications across interconnected networks of computers with diverse hardware architectures and various operating systems. TCP/IP includes standards for how computers communicate and conventions for connecting networks and routing traffic.

TRANSMISSION GROUP:

In SNA routing, one or more parallel communications links treated as one communications facility.

TRANSMISSION:

The transfer (transmission) of information from one point to another point

TRANSMISSION BLOCK:

A grouping of data characters (bytes) sent through the transmission channel, with synchronization coding patterns and block framing bits or characters and would normally include error control functions.

TRANSMISSION CONTROL CHARACTERS:

A set of non-alphanumeric characters used to facilitate or control data transmission. A communications protocol function. Refer to ASCII control Characters.

TRANSMISSION IDENTIFIER LINE (TI):

A message identifier sequence transmitted ahead of all messages in a discontinued message switching system.

TRANSMISSION MEDIUM (MEDIA):

Any facility, line, cable, etc. used to carry a representation (analog ‘voice’, digital, electrical, optical, etc.) of information.

TRANSMISSION MEDIUM 10Base2:

Refers to a transmission medium specified by IEEE 802.3 which carries information at 10 million bits per second (Mbps) in the base-band form using low cost coaxial cable up to 200 meter non-repeater runs; often called ‘Thin Wire Ethernet’.

TRANSMISSION MEDIUM 1Base5:

An IEEE 802.3 transmission medium that carries information at 1.0 million bits per second (Mbps) in the base-band form using twisted pair conductors up to 500 meter non-repeater runs.

TRANSMISSION MEDIUM 10Base5:

A transmission medium specified by IEEE 802.3: Carries information at 10 million bits per second (Mbps) in the base-band form using special 50 ohm coaxial cable up to 500 meter non-repeater runs; often called "Thick Wire Ethernet".

TRANSMISSION MEDIUM 10baseT:

An IEEE 802.3 transmission medium: Carries information at 10 million bits per second (Mbps) in a base-band form using twisted pair conductors.

TRANSMISSION SPEED:

A measurement of data transfer speed (bps) over a circuit (line). There is a difference between ‘line-speed’ (MODEM to MODEM), and Data Terminal Equipment (DTE) speed (PC to the MODEM). Data compression, circuit conditions and equipment can and will determine actual transmission speed. I.e. a 56Kbps MODEM may only transmit at 28K to 35K due various detrimental conditions.

TRANSMISSION (TRANSPORT) CONTROL PROTOCOL/INTERNET PROTOCOL:

See TCP/IP

TRANSMIT:

To send out a signal over data communications media such as optical fiber, copper wire, or via radio waves through the atmosphere, from one station to another; To send information (data) electronically

TRANSMIT DATA (Send Data):

RS-449 (Pin 4A & 22B) – DTE (Data Terminal Equipment) data send circuit.

TRANSMIT SIGNAL TIMING (Terminal Timing):

RS-449 (Pin 17A & 35B) – Transmission timing signals (clock) originating (provided) at the DTE (Data Terminal Equipment.

TRANSMITTER-DISTRIBUTOR:

See TD

TRANSMITTER SIGNAL TIMING (Receive Timing):

RS-449 (Pin 8A & 26B) – Transmission timing signals (clock) originating at the DCE (Data Communication Equipment) end, that are used by the DTE (Data Terminal Equipment) for receiving.

TRANSMITTING STATION ID (TSID) STRING:

A string that specifies (identifies) the transmitter subscriber ID sent by the fax machine when sending a fax to a receiving machine. This string is usually a combination of the fax or telephone number and the name of the business. It is often the same as the called subscriber ID.

TRANSPAC:

A French Packet Switched network

TRANSPARENCY / TRANSPARENT MODE:

References digital communication in which control characters are not recognized; transmission of data (bit patterns) of any form without regard to character interpretation; or a communication channel operation where the user has full and free use of the total available bandwidth.

TRANSPARENT GIF:

A type of GIF (Graphic Interchange Format) image where one color, usually the background of the image, has been selected to appear as transparent: When placed on a web page, any background color or tiled image will show through the transparency.

TRANSPONDER:

A device that receives and amplifies a signal, and then retransmits it at a different frequency;

A component used in a satellite communication environment, responsible for receiving an up-link signal, converting that signal to a higher frequency, and transmitting as a down-link signal to an earth station.

TRANSPORT CONTROL PROTOCOL CLASS FOUR (TP4):

An International Standards Organization transport layer protocol: Designated as International Standards Organization (ISO), IS 8073, class Four Service.

TRANSPORT LAYER:

The name of the layer in the Open System Interconnection (OSI) network responsible for the end to end transmission integrity through a network: Another function of this layer is data flow control and transmission speed matching.

Layer 4 of the OSI reference model: This layer is responsible for reliable network communication between end nodes. The transport layer provides mechanisms for the establishment, maintenance, and termination of virtual circuits, transport fault detection and recovery, and information flow control.

TRANSPORT LAYER SECURITY (TLS):

A standard protocol that is used to provide secure Web communications on the Internet or intranets: It enables clients to authenticate servers or, optionally, servers to authenticate clients. It also provides a secure channel by encrypting communications. TLS is the latest and a more secure version of the SSL protocol.

TRANSPORT PROTOCOL DATA UNIT (TPDU):

The form into which the transport layer in a network will format data for use and recognition.

TRANSVERSE PARITY CHECK:

Refers to a type of parity checking

TRAP:

In Simple Network Management Protocol (SNMP), a message sent by an agent to a management system indicating that an event has occurred on the host running the agent.

TRAP DOOR:

Hidden computer flaw known to an intruder, or a hidden computer mechanism (software) installed by an intruder, who can activate the trap door to gain access to the computer without being blocked by security services or mechanisms.

TRBRF:

Token Ring Bridge Relay Function: Internal multi-port bridge function used to interconnect rings to form a domain

TRC:

Transmission Release Code: A control character indicating protocol checks are normal and transmission can begin.

TRCRF:

Token Ring Concentrator Relay Function: A logical ring domain formed by defining groups of ports that have the same ring number.

TREE:

Refers to a network topology where only one route exists between any two nodes.

In data communications, a tree is a form of network topology having only one path between any two network nodes, so that the network resembles a branching tree, similar to CATV networks.

TRIBUTARY:

See Terminal

TRELLIS CODING:

Refers to an error checking method used in some high speed MODEMs where information concerning signal phase and amplitude is added to individual signal elements.

TRIBIT:
A technique used by a MODEM where the status of three bits is transmitted simultaneously.

TRIBUTARY STATION:

A device (terminal) on a multipoint line: Usually not the controlling station; may be called a slave station.

TRIGGERED EVENT:

An action built into a virus set off by a specific condition. Examples include a message displayed on a specific date or reformatting a hard drive after the 10th execution of a program.

TRIP:

Token Ring Interface Processor: High-speed interface processor on the Cisco 7000 series routers. The TRIP provides two or four Token Ring ports for interconnection with IEEE 802.5 and IBM Token Ring media, with ports independently set to speeds of either 4 or 16 Mbps.

TRISL:

Token Ring Inter-Switch Link

TRIVAL FILE TRANSFER PROTOCOL (TFTP):

A Unix based file transfer protocol.

TROJAN HORSE:

A program: That usually does not replicate or produce self copies, but will compromise (damage) the security of the computer system. E-mail sent in the form of a joke program or software formats.

TROJAN HORSE PROGRAM:

A Trojan horse program is a malicious program that pretends to be a benign application; a Trojan horse program purposefully does something the user does not expect. Trojans are not viruses since they do not replicate, but Trojan horse programs can be just as destructive.

Many people use the term to refer only to non-replicating malicious programs, thus making a distinction between Trojans and viruses.

TROLL:

A message posted to a newsgroup or mailing list or message board to bait people to answer. Trolling is a form of harassment that can take over a discussion. Well meaning defenders can create chaos by responding to trolls. The best response is to ignore it.

TROUBLESHOOT:

To search for the cause of a malfunction or erroneous program behavior, in order to correct the malfunction.

TRT:

See Token Rotation Timer

TRUE TYPE FONTS:

Scalable Fonts: Sometimes generated as bitmaps or soft fonts, depending on the capabilities of the printer. TrueType fonts are device-independent fonts that are stored as outlines. They can be sized to any height, and they can be printed exactly as they appear on the screen.

TRUNCATED BINARY EXPONENTIAL BACK OFF:

Another name for Exponential Back-Off used in IEEE 802.3 LAN systems.

TRUNK:

1) Physical and logical connection between two switches across which network traffic travels. A backbone is composed of a number of trunks.

2) In telephony, a phone line between two COs or between a CO and a PBX.

3) A circuit connecting switching or distribution centers; Or a high speed channel between two computer systems.

TRUNK GROUP:

Multiple connections: Between two switching centers or individual message distribution points.

TRUST FILE PKI:

Non-hierarchical PKI in which each certificate user has a local file, used by application software,  of public-key certificates that the user trusts as starting points (roots) for certification paths.

TRUST RELATIONSHIP:

A logical relationship established between domains to allow pass-through authentication, in which a trusting domain honors the logon authentications of a trusted domain. User accounts and global groups defined in a trusted domain can be given rights and permissions in a trusting domain, even though the user accounts or groups don't exist in the trusting domains directory.

TR VLAN:

Token Ring virtual LAN

TS:

Magnetic Tape Station

TSAPI:

Telephony Services Application Programming Interface: A call control model developed by Lucent and Novell.

TSC:

1) Transmitter start code: A control character that causes the transmitter to begin transmission of a message.

2) U. S. Army AUTODIN site (ASC) designation: ‘Telecommunications Switching Center

TSI:

1) Transport Session Identifier: Unique identifier used by both the PGM Host and PGM Router; assistance features used to identify each individual session.

2) Transmitting Subscriber Information: Frame that can be sent by the caller with the caller's telephone number that can be used to screen calls.

TSL-1:

Task Sequencing Language: Language for specifying sequences for tasking events in ADA compiler programs.

TSO:

Telecommunications Service Order

TSP:

See Twisted Pair Cable

T-SPAN:

A T- carrier telephone circuit

TSPS:

See Traffic Service Position System

TSR:

1) Telecommunications Service Request

2) Terminate and Stay Resident: TSR programs stay in memory after being executed. TSR programs allow the user to quickly switch back and forth between programs in a non-multitasking environment, such as MS-DOS. Some viruses are TSR programs that stay in memory to infect other files and program.

TSS:

Traffic Service Section

TSU (RMS):

Tape Search Unit (Records Management system): Off-line message recovery and retrieval computer.

TTD:

See Temporary Text Delay

TTTN:

Tandem Tie Trunk Network: An arrangement that permits sequential connections of tie trunks between PBX and Centrex® locations. Tandem operation permits two or more dial tie trunks to be connected at a tandem center to form a through connection.

TTRT:

See Target Token Rotation Time

TTY:

Teletypewriter / Teletype: A Send and/or Receiving communications device similar to a standard electric typewriter with a paper tape reader. Most of these units are of the ASR (Automatic Send and Receive) type of equipment, which consisted of a console and transmitting and receiving units. The transmitting unit was usually a paper tape transmitter. In addition line and protocol control devices can be used. The communications code is usually the Baudot (modified) or ASCII code set.

TTYNET:

Teletypewriter Network: A network of Teletypewriter (TTY) communication devices connected to an ASC (AUTODIN Switching Center).

TTY PROTOCOL:

A simple asynchronous data communication protocol used to control the transmission of individual characters. Start and stop bits are used and error detection is performed using an individual character parity check bit.

TTY TRANSMISSIION:

A form of data communications: Usually asynchronous Baudot or ASCII, using teletypewriter devices.

TUD:

Trunk Up-Down: Protocol used in ATM networks that monitors trunks and detects when one goes down or comes up. ATM switches send regular test messages from each trunk port to test trunk line. If a trunk misses a given number of these messages, TUD declares the trunk down. When a trunk comes back up, TUD recognizes that the trunk is up, declares the trunk up, and returns it to service.
TULIP:

TCP and UDP over Lightweight IP: Protocol for running TCP and UDP applications over ATM

TUNIP:

TCP and UDP over Nonexistent IP: Protocol for running TCP and UPD applications over ATM.

TUNNEL:

Secure communication path between two peers, such as two routers

A logical connection over which data is encapsulated: Typically, both encapsulation and encryption are performed and the tunnel is a private, secure link between a remote user or host and a private network.

TUNNELING:

Architecture that is designed to provide the services necessary to implement any standard point-to-point encapsulation scheme

A virus technique designed to prevent anti-virus applications from working correctly. Anti-virus programs work by intercepting the operating system actions before the OS can execute a virus. Tunneling viruses try to intercept the actions before the anti-virus software can detect the malicious code. New anti-virus programs can recognize many viruses with tunneling behavior.

TUNNEL SERVER:

A server or router that terminates tunnels and forwards traffic to the hosts on the target network

TURNAROUND TIME:

References the actual time consumed in a half duplex transmission system for a device to change operational status from transmit to receive; Could also refer to response time while awaiting a reply to a transmitted message.

TURN KEY:

A term used to describe a vendor provided ‘ready-to-run’ and self-contained, data system requiring little or no user setup.

TUV:

German test agency that certifies products to meet European safety standards

TWIN AXIAL CABLE:

A transmission cable: Contains two separate internal conductors and an axial (outside) grounded shield.

TWISTED PAIR:

Telephone companies commonly run twisted pairs of copper wires to each customer household. The pairs consist of two insulated copper wires twisted into a spiral pattern. Although originally designed for plain old telephone service (POTS), these wires can carry data as well as voice. New services such as ISDN and ADSL also use twisted-pair copper connections.

TWISTED PAIR CABLE:

Groups of two insulated 18 to 26 gauge copper wires twisted around each other to reduce induction (and thus interference) from one wire to the other. Several sets of twisted-pair wires are bundled together composing a single cable. Shielded Twisted Pair (STP) has a shielding wrapped around the insulated wires for greater interference immunity. Unshielded Twisted Pair (UTP) does not have shielding and is commonly used in MODEM telephone wiring systems.

TWO-WIRE CIRCUIT:

An analog send and receive channel (line) transmitting data in one direction at a time, half-duplex operation. In DC operation the two-wire circuit could be used for full duplex operation.

TWO WAY ALTERNATE OPERATION:

A single line supporting data transmission in one direction only: Cannot send and receive simultaneously; usually referred to as half duplex operation.

TWO-WAY SIMULTANEOUS:

Mode that allows a router configured as a primary SDLC station to achieve better utilization of a full-duplex serial line. When TWS is enabled in a multi-drop environment, the router can poll a secondary station and receive data from that station while it sends data to or receives data from a different secondary station on the same serial line.

TWO-WAY SIMULTANEOUS OPERATION:

Simultaneous send and receive data transmission: Usually referred to as full duplex operation.

TWR:

Transmitter-Receiver

TWX:

Teletypewriter Exchange Service: Originally an AT&T communications service product, now the property of Western Union Corporation under the product name Telex II, transmitting ASCII code at 100 wpm. TWX is interfaced to a number of other services of different codes and speeds through a mainframe-based protocol converter Western Union calls InfoMaster.

TYMNET:

An USA packet switched network.

TYPE A COAX:

A data communications protocol operating at 2.35 mbps used in an IBM 3270 terminal environment to provide data transfer between a 3274 Control Unit and attached terminals and printers.

TYPE A TRAFFIC:

Transactional traffic: Typically, this is conversational traffic exchanged between a host and its ASCU(s) for terminal queries and responses; another form of Type A traffic is called host-to-host traffic.

TYPE B TRAFFIC:

Messaging traffic: Typically, this is e-mail application traffic in IATA-compliant format

TYPE 1 FONT(s):

Scalable fonts designed to work with PostScript devices.

TYPE 1 OPERATION:

IEEE 802.2 (LLC) connectionless operation

TYPE 2 OPERATIONS:

IEEE 802.2 (LLC) connection-oriented operation

TYPEFACE:

A set of characters that share common characteristics:  Such as stroke width and the presence or absence of serifs, short lines at the upper and lower edges of characters.