Glossary- U
A Data Communication Historical series
by Bob Pollard

HOME                        INDEX

U INTERFACE:

The interface between the Telco and the user: Also known as the local digital subscriber line (DSL) loop.

UA:

Unnumbered Acknowledgement

UAC:

User Agent Client: A client application that initiates the SIP request

UAL:

User Application Layer: Refers to the open system interconnection (OSI) model.

UART:

Universal Asynchronous Transmitter and Receiver (chip): A device that converts parallel data (e.g. 8 bit bytes) into a serial data stream which can be transmitted over a telephone line or circuit. The device also collects (receives) serial bits of a character from a transmission line and assembles them after stripping the framing characters, then stores them into a receiving register, and then transfers the character as an 8-bit parallel character to the CPU. I.e. the UART is both receiving and transmitting device encapsulated in the same chip.

UAS:

1) Unavailable Seconds: The PM parameter that measures the duration in seconds in which the path is unavailable; the time interval in seconds, starting with the first of 10 or more consecutive Severely Errored Seconds (SES) and ending at the beginning of 10 consecutive non-SES.

2) User Agent Server: A server application that contacts the user when a SIP request is received, and then returns a response on behalf of the user. The response accepts, rejects, or redirects the request.

UAUTH:

User Authentication

UB NET/ONE:

Ungermann-Bass Net/One: Routing protocol, developed by UB Networks, that uses hello packets and a path-delay metric, with end nodes communicating using the XNS protocol. There are a number of differences between the manner in which Net/One uses the XNS protocol and the usage common among other XNS nodes.

uBR:

Universal Broadband Router: The uBR7246 and uBR7223 are DOCSIS-compliant cable MODEM termination systems (CMTSs). The uBR900, uBR904, and uBR924 are DOCSIS-certified cable MODEM(s).

UBR:

Unspecified Bit Rate: QoS class defined by the ATM Forum for ATM networks. UBR allows any amount of data up to a specified maximum to be sent across the network but there are no guarantees in terms of cell loss rate and delay.

UBR+:

Unspecified Bit Rate Plus: UBR service complemented by ATM switches that use intelligent packet discard mechanisms, such as EPD or TPD.

UCD:

Uniform Call Distributor: A device located at a telephone office or part of a wireless private automatic branch exchange (PABX) that distributes incoming calls evenly among devices or individuals.

UCM:

Universal Call Model: Used interchangeably with LCM

UCP:

1) User Control Point: Cisco UCP is a carrier-class service policy administration system that enables personalized IP services.

2) UNIX-to-UNIX Copy Program: Protocol stack used for point-to-point communication between UNIX systems.

See Unix-to-Unix Copy

UDLC:

Universal Data Link Control: The Unisys bit-oriented communications standard

UDLP:

UniDirectional Link Protocol: Protocol used by inexpensive, receive-only antennas to receive data via satellite.

UDP:

User Datagram Protocol: UDP uses IP (Internet Protocol) for packet delivery and, basically, is unreliable because UDP does not use handshaking before exchanging data and therefore acknowledgments and guaranteed delivery are not available. UDP relies on higher protocol layers to provide end to end data delivery and integrity.

U-FRAME:

Unnumbered Frame: One of three SDLC frame formats.

UHF:

Ultra-High Frequency: The band of frequencies between 300 MHz and 3 GHz

UI:

Unnumbered Information

UI-FRAME:

Unnumbered Information Frame:

UIO:

Universal I/O serial port (Cisco router)

UIO MODULE:

Universal Input Output module: The STDX module that allows a variation in connections to input/output (I/O) panels.

UKERNA:

UK Education and Research Networking Association

UL:

Underwriters Laboratories: Independent agency within the United States that tests product safety.

U-LAW:

Companding technique commonly used in North America: U-law is standardized as a 64-kbps CODEC in ITU-T G.711.

ULP:

Upper-Layer Protocol: Protocol that operates at a higher layer in the OSI reference model, relative to other layers. ULP is sometimes used to refer to the next-highest protocol, relative to a particular protocol, in a protocol stack.

ULSI:

Ultra Large Scale Integration: A term describing an ultra- high density microchip containing over 10,000 circuits.

ULTIMEDIA:

An IBM product that supports both Ultimotion & INDEO video

ULTIMOTION:

An IBM video compression algorithm

ULTRA SCSI:

Variation of SCSI - higher speed SCSI (data rates as high as 40MBytes/sec).

ULTRIX SYSTEM:

A designation for the Digital Equipment enhanced native-mode UNIX operating system.

UMBRELLA PRICES:

Refers to regulated prices for various communication services offered by telephone (communication) companies

UMTS:

1) Universal Mobile Telephone Service: A 3G mobile wireless telecommunications system under development by the Third Generation Partnership Project (3GPP)

2) Universal Mobile Telecommunications System: An evolution of GSM (Global Standard for Mobile) technology to 3G: The underlying transmission standard is WCDMA (Wideband CDMA).

UNALLOCATED SPACE:

Available disk space that is not allocated to any volume: The type of volume that a user can create on unallocated space depends on the disk type. On basic disks, a person can use unallocated space to create primary or extended partitions. On dynamic disks, a person can use unallocated space to create dynamic volumes.

UNATTENDED OPERATION:

An automatic device (terminal) feature: Allows the transmission and reception of messages without human operators.

UNBALANCED / UNBALANCED TO GROUND:

A term used to describe the condition present in a two wire circuit when the impedance-to- ground on one wire is different from that of the other wire. Contrast with balanced, balanced-to-ground.

UNBALANCED CONFIGURATION:

HDLC configuration with one primary station and multiple secondary stations

UNBUNDLED:

A class of products where various elements of a system, including services, equipment, software, and training are sold separately

UNBUNDLED RATES:

The elements that comprise a service or groups of equipment are listed separately and the charge for each component of the service is identified.

UNBUNDLING:

Refers to the requirement that local telephone companies must offer long-distance companies and other competitive communication provider’s access to their network facilities; Essential facilities are basically defined as services or functions which are only available from a particular provider (no other reasonable alternatives exist) and would normally include capabilities that competitors require in order to serve their customers.

UNC:

Universal Naming Convention: This is the standard for naming network drives. For example, UNC directory path has the following form: \\server\resource-pathname\subfolder\filename.

UNCONTROLLED TERMINAL:

‘Free Wheeling’: A terminal containing no polling or control logic and is always online to the CPU.

UNDOCK:

To detach a laptop or other portable computer from a docking station.

UNECONOMIC ENTRY:

Refers to a situation in which an industry's long-term unit costs of producing goods or services increase because competitors enter the same business field. For example, when the prices of long distant services are artificially maintained above their costs in order to subsidize local services, a competitor could undercut the existing long distant service price. This would normally result in higher unit costs for the competitor. Also this would eventually result in an increase in overall unit costs.

UNI:

User-to-Network Interface: ATM Forum specification that defines an interoperability standard for the interface between ATM-based products (router / ATM switch) located in a private network and the ATM switches located within the public carrier networks.

UNIBUS:

A single high-speed bus structure shared by the processor, memory, and peripherals

UNICAST:

In data communications networks, to transmit data from one terminal to another: Such as from client to server, or from server to server.

UNICAST ADDRESS:

Address specifying a single network device.

UNICAST RPF:

Unicast Reverse Path Forwarding: An input function that is applied only on the input interface of a router at the upstream end of a connection.

UNICODE:

A character encoding standard developed by the Unicode Consortium that represents almost all of the written languages of the world: The Unicode character repertoire has multiple representation forms, including UTF-8, UTF-16, and UTF-32. Most Window interfaces use UTF-16 (Unicode Transmission Format).

UNICODE CHARACTER SYSTEM (UCS):

An international standard character set reference that is part of the Unicode standard. The most widely held existing version of the UCS standard is UCS-2, which specifies 16-bit character values currently accepted and recognized for use to encode most of the world's languages.

UNICODE TRANSMISSION FORMAT 8 (UTF-8):

A character set for protocols evolving beyond the use of ASCII. The UTF-8 protocol provides for support of extended ASCII characters and translation of UCS-2, an international 16-bit Unicode character set. UTF-8 enables a far greater range of names than can be achieved using ASCII or extended ASCII.

UNIFORM CALL DISTRIBUTOR (UCD):

A device located at the telephone office or in a PABX which distributes incoming calls evenly among individuals; may be called a ‘call sequencer’.

UNIFORM RESOURCE LOCATOR (URL):

An address that uniquely identifies a location on the Internet: A URL for a World Wide Web site is preceded with http://; example: the fictitious URL http://www.example.microsoft.com/. A URL can contain more detail, such as the name of a page of hypertext, usually identified by the file name extension .html or .htm.

UNIFORM SERVICE ORDER CODE (USOC):

A set of codes developed by the Bell System and used by local telephone companies as a standard means of identifying service or equipment for billing purposes.

UNIFORM SPECTRUM RANDOM NOISE:

White Noise: Noise that is equally distributed across all frequencies. For example, background noise heard over the telephone.

U-NII:

Unlicensed National Information Infrastructure: Term coined by federal regulators to describe the access of information to citizens and business. Equivalent to the term ‘information superhighway’, it does not describe system architecture or topology.

UNINET:

A data communications common carrier offering: X.25 PDN.

UNINSTALL:

When referring to software: The act of removing program files and folders from the hard disk and removing related data from the registry so the software is no longer available.

When referring to a device: The act of removing the corresponding device drivers from the hard disk and physically removing the device from the computer.

UNINSURED TRAFFIC:

Traffic within the excess rate: The difference between the insured rate and the maximum rate for an ATM VCC.

UNINTERRUPTIBLE POWER SUPPLY (UPS):

A device connected between a computer and a power source to ensure that power is not interrupted. UPS devices may use batteries or engine powered systems to keep the computer running for a period of time after a power failure. UPS devices may provide protection against power surges and brownouts as well.

UNI-OSP:

Feature that allows the authentication of outgoing Voice over IP (VoIP) telephone connections, using the Open Settlement Protocol (OSP)

UNIPOLAR:

A signal stream in which all one bits are the same voltage polarity: Zero bits normally are 0 volts.

 UNIPOLAR RETURN-TO-ZERO:

References a unipolar signal with a 50 percent duty cycle for each pulse

UNIT:

1) A manageable piece of related code.

2) An estimated group usage per pay phone that is used to determine estimated usage.

UNIT CALL:

Refers to a traffic unit of one hundred calls per seconds

UNITY GAIN:

In broadband networks the balance between signal loss and signal gain through amplifiers

UNIVERSAL ACCESS NUMBER:

A single digit number, that when dialed from anywhere in the country can reach sites in other parts of the country.

UNIVERSAL GROUP:

A security or distribution group that can be used anywhere in the domain tree or forest. A universal group can have members from any Windows domain in the domain tree or forest. It can also include other universal groups, global groups, and accounts from any domain in the domain tree or forest. Rights and permissions must be assigned on a per domain basis, but can be assigned at any domain in the domain tree or forest.

Universal groups can be members of domain local groups and other universal groups, but they cannot be members of global groups. Universal groups appear in the global catalog and should contain primarily global groups.

UNIVERSAL NAME SPACE:

The various sets of unique object identifiers in a domain, network or enterprise, etc.

UNIVERSAL NIGHT ANSWER:

A private branch exchange (PBX) feature: Permits any station to dial a single digit number in order to answer an incoming trunk call when no attendant is present.

UNIVERSAL SERIAL BUS (USB):

A high-speed (12Mbps) serial port for PCs: An external bus that supports Plug and Play installation: USB devices can be connected and disconnected without shutting down or restarting the computer. A single USB port can connect up to 127 peripheral devices, including speakers, telephones, CD-ROM drives, joysticks, tape drives, keyboards, scanners, and cameras.

UNIVERSAL SERVICE:

Refers to a National Communications Act of 1934, where wire and radio communication services, with adequate facilities at reasonable charges would be made available, as far as possible, to all the people of the United States. Today, a very large number of telephone customers receive their service through a subsidized system. Due to the accelerating pace of technology the concept of universal service is being re-evaluated.

UNIVERSAL SERVICE ORDER CODE (USOC):

The information in coded form for billing purposes; used by the local telephone company when processing service orders and service equipment records.

UNIVERSALITY:

Accessibility to telephone services at an affordable price

UNIX:

Unix originated in the early 1970’s as a general-purpose operating system. A large part of the Internet is hosted on Unix machines since the early 1990’s. Unix has many varieties, such as

Xenis, Ultrix, GNU, and Linux and runs on a variety of platforms. Unix is designed for use by many people at the same time (multi-user) and has TCP/IP (Transmission Control Protocol / Internet Protocol) built-in. It is probably the most common operating system for servers on the Internet.

UNIX-TO-UNIX COPY (UUCP):

1) Originally a Unix program that permitted file transfer between two Unix-based PCs through a dial-up connection.

2) A Unix networking protocol or any network using that protocol.

UNMIRRORED SERVER:

A server that uses only one disk drive and one disk channel that includes a controller, power supply, and interface cabling.

UNNUMBERED FRAMES:

HDLC frames used for various control and management purposes, including link startup and shutdown and mode specification.

UNRATEABLE:

Implies that insufficient information is available to determine the correct rate

UNSHIELDED TWISTED PAIR (UTP):

Twisted-pair cabling without a protective (grounded) covering: For example: Data-grade Twisted Pair (DTP) and Distributed inside Wire (DIW).

UN-TRUSTED PROCESS:

A system process that cannot affect the state of system security through incorrect or malicious operation, usually because its operation is confined by a security kernel

UPC:

1) Universal Product Code: The ‘bar code’ used to identify consumer and industrial products in mechanized inventory systems.

2) Usage Parameter Control

UPGROUPING:

A process that occurs when the telephone count in an exchange outgrows its current rate group and must move to the next highest local rate group; each rate group has a minimum and a maximum number of permitted telephone lines, which determines the basic local rate.

UPL:

User Program Layer: The Open System Interconnection (OSI) model.

UPLINK: The connecting link for the earth-to-satellite transmission channel

UPLOAD:

The act of transferring a file from a local computer connected to the Internet to a remote computer or terminal; the opposite of download.

UPS:

Un-interruptible Power Supply: A secondary power supply that provides service when the main AC Power degrades or fails. An UPS unit may include batteries or a motor generator (MG) set with flywheel energy storage (a no-break system).

UPS SERVICE:

A service that manages an Uninterruptible Power Supply (UPS) connected to a computer.

UPSR:

Unidirectional Path Switched Ring: Path switched SONET rings that employ redundant, fiber-optic transmission facilities in a pair configuration. One fiber transmits in one direction and the backup fiber transmits in the other. If the primary ring fails, the backup takes over.

UPSTREAM:

1) The relative position of two stations in a ring: A station is considered upstream from its neighbor if it receives a token before its neighbor receives the token. Or, refers to the end-user to host (transmit, upload) direction and the sending direction from an end-user to the network.

2) Set of frequencies used to send data from a subscriber to the head-end

UPTIME:

The period of time that a computer application or data communications link would be available to the user on an uninterrupted basis; contrast with downtime.

UPWARD COMPATIBLE:

An application program having the characteristics of compatibility with an enhanced program mode or operation; example: a newer release or version operating system.

UR:

User Registrar: One of the software products included in the Cisco Subscriber Registration Center (CSRC) product. UR enables cable network subscribers to self-provision account registration, and to activate their cable MODEM and PC over the cable network using a Web user interface. User Registrar activates subscriber devices with account-appropriate privileges through updates to an LDAP directory.

URI:

Uniform Resource Identifier: Type of formatted identifier that encapsulates the name of an Internet object; labels it with an identification of the name space, thus producing a member of the universal set of names in registered name spaces, as well as addresses referring to registered protocols or name spaces.

URL:

Uniform Resource Locator / Universal Resource Locator: URLs are the Internet equivalent of addresses. Like other types of addresses, the general to the specific portions of the address is broken down. For example:

http://www.datacom.net/downloads/datacom

First the protocol:

http:/

Then the server address or domain:

/www.datacom.net

Then the directory:

/downloads/ datacom

Where the file index.html resides

URN:

Uniform Resource Name: – A URL (Uniform Resource Locator) that is supposed to be available for along time, and the URN (address) assigned to a resource implies the data will be available at that address for a lengthy period of time.

US:

1) Microsecond; one-millionth of a second

2) FS, GS, RS, US: File Separator, Group Separator, Record Separator, and Unit Separator: Information separators used within data in an optional fashion. The hierarchical relationship will usually be FS is the most inclusive, then GS, then RS and US the least inclusive.

U.S. HALF CIRCUIT:

A logical circuit between the U.S. International Test and Maintenance Center (ITMC) and The Theoretical Midpoint (TMP)

USAGE COUNT:

Refers to a count indicating the number of times a program, circuit or piece of equipment is used during a certain period of time.

USAGE DURATION MONITOR:

A monitoring device that alerts the communications system when a decrease in trunk calls duration occurs.

USAGE SENSITIVE PRICING (USP):

Charges for service(s) that are based on usage

USAISC:

United States Army Information Systems Command: See USASTRATCOM.

USART:

Universal Synchronous/Asynchronous Receiver/Transmitter: A semiconductor device performing synchronous/asynchronous conversion from a communications processor to the correct format for data transmission.

USASTRATCOM:

United States Army Strategic Communications Command: The Army term for their Electro-mechanical Relays and switching centers.

USB

Universal Serial Bus: 1.5 or 12 megabits per second serial interface for PC/peripheral connection, 2 different modes. See USB Port

USB PORT:

Universal Serial Bus Port: An interface on the computer that enables a user to connect a Universal Serial Bus (USB) device: USB is an external bus standard that enables data transfer rates of 12 Mbps (12 million bits per second).

USE CASE (Scenario):

A documented set of typical interaction dialogs between the users of a system and a proposed system. Scenarios are developed during the analysis phase of system development to assist in understanding business events, objects and interactions. Use case scenarios facilitate communication between the people who request a system, analysts, developers and testers. They are used to validate understanding, and to identify normal and special use situations. Scenarios clarify an evolving agreement between requesters and development teams; similar to the Request for Proposal (RFP) document.

USENET:

Yoos-net or yooz-net, from `Users Network': A world-wide system of discussion groups, with comments passed among hundreds of thousands of machines. Not all USENET machines are on the Internet. USENET is completely decentralized, with over 10,000 discussion areas, called newsgroups.

A distributed b-board (bulletin board) system supported mainly by Unix machines; originally implemented in 1979-1980 by Steve Bellovin, Jim Ellis, Tom Truscott, and Steve Daniel at Duke University. It has swiftly grown to become international in scope and is now probably the largest decentralized information utility in existence. As of early 1996, it hosted over 10,000 news-groups involved in technical articles, news, discussion, chatter and flamage (See Flame).

USER:

A person who uses a computer and associated network facilities

USER ACCOUNT:

A record that consists of all the information that defines a user to Windows: This includes the user name and password required for the user to log on, the groups in which the user account has membership, and the rights and permissions the user has for using the computer and network, and accessing their resources. For Windows XP Professional and member servers, user accounts are managed with Local Users and Groups. For Windows Server domain controllers, user accounts are managed with Microsoft Active Directory Users and Computers.

USER CLASS OF SERVICE:

A service category of data transmission: A network where the data signaling rate and terminal operating mode are standardized.

USER DEFINED MACRO:

REACT 2000 option: Allows a tester to record the steps taken to test a circuit and to later play back those steps automatically. This allows the information to be used to test another circuit of the same type.

USER ID:

An approved unique identifier associated with a user name on a server system.

USER NAME:

A unique name identifying a user account to Windows: An accounts user name must be unique among the other group names and user names within its own domain or workgroup.

USER NETWORK (Usenet):

Usenet is an Internet tool used for sharing ideas and information among computer hosts. The users communicate through news groups, which is a forum for discussing particular interests or topics. Usenet news can be accessed through a WWW (World Wide Web) browser or through networks which can exchange electronic mail.

USER-TO-NETWORK INTERFACE (UNI):

The reference point where the protocols between customer premises equipment (CPE) and a carrier network must be defined: An UNI specification defines in detail the Layer 1 and Layer 2 and perhaps Layer 3 protocols

USER PASSWORD:

The password stored in each user's account. Each user generally has a unique user password and must type that password when logging on or accessing a server or system.

USER PRINCIPAL NAME:

A user account name (user logon name) and a domain name identifying the domain in which the user account is located. This is the standard usage for logging on to a Windows domain. The format is: user@domain.com (similar to e-mail address).

USER PRINCIPAL NAME (UPN) SUFFIX:

The UPN suffix is the part of the user principal name to the right of the @ character. The default UPN suffix for a user account is the DNS (Domain Name System) name of the domain that contains the user account. Alternative UPN suffixes may be added to simplify administration and user logon processes by providing a single UPN suffix for all users. The UPN suffix is only used within the Active Directory forest and is not required to be a valid DNS domain name.

USER PROFILE:

A file that contains configuration information for a specific user: Such as desktop settings, persistent network connections, and application settings. Each user's preferences are saved to a user profile that Windows uses to configure the desktop each time a user logs on.

USER RIGHTS:

Tasks that a user is permitted to perform on a computer system or domain: There are two types of user rights: privileges and logon rights. An example of a privilege is the right to shut down the system. An example of a logon right is the right to log on to a computer locally. Both types may be assigned by administrators to individual users or groups as part of the security settings for the computer.

USER PORT:

In the context of wavelength routing, a user port is a port that originates or terminates on a node; in other words, it is a port on the NE that points to a non-wavelength router NE.

USERS:

A special group that contains information on all users who have user permissions on the server: When a Macintosh user assigns permissions to everyone; those permissions are given to all the group users and guests.

USOC:

Refer to Uniform Service Order Code

USP:

Refer to Usage Sensitive Pricing

USRT:

1) Universal Synchronous Receiver and Transmitter: Same function as UART, except it handles 8 bit characters without framing and detects SYNC characters for framing purposes. See UART.

2) A device which controls data transmission and reception between two devices via transmission lines using a continuous synchronous clock (a system which transfers data continuously by synchronizing with characters). Normally, this type of device uses synchronous transfer control protocols such as HDLC, SDLC and Bisync.

UTC:

Coordinated Universal Time: Time zone at zero degrees longitude: Formerly called Greenwich Mean Time (GMT) and Zulu time.

UTILITY / UTILITY PROGRAM:

A computer program designed to perform a task required by many or most of the computing systems users, the most common of which are those that copy information from one medium to another and those used to streamline an operation.

UTILITY SERVICE:

A service where the choice of suppliers is limited

UTP:

See Unshielded twisted Pair

UTS:

Universal Terminal Support: A data link layer protocol (P1024C) that runs in full-duplex mode over synchronous serial (V.24) lines and uses the ASCII character set.

UUDECODE:  

UNIX-to-UNIX Decode: Method of decoding ASCII files that were encoded using uuencode.

UUENCODE:

UNIX-to-UNIX encoding: Method of converting binary files to ASCII so they can be sent over the Internet via e-mail. The name comes from its use by the UNIX operating system's uuencode command.

UUENCODE:

Unix to Unix Encoding: A method for converting files from binary to ASCII (text) so they can be sent across the Internet via E-mail.

UVM:

Universal Voice Module

UVM-C:

Universal Voice Module-Channelized

UVM-U:

Universal Voice Module-Unchannelized