UBR Unspecified Bit Rate:
UBR is an ATM service category which does not specify traffic related service guarantees. Specifically, UBR does not include the notion of a per-connection negotiated bandwidth. No numerical commitments are made with respect to the cell loss ratio experienced by a UBR connection, or as to the cell transfer delay experienced by cells on the connection.

UCD User Centered Design.

UCE See Unsolicited Commercial Email (UCE).

UCS
Universal Character Set (Universal Multiple-Octet Coded Character Set) of ISO ISO 10646.

UDP (User Datagram Protocol)
A non-guaranteed network packet protocol implemented on IP that is far faster than TCP because it doesn’t have flow-control overhead. UDP can be implemented as a reliable transport when some higher-level protocol (such as NetBIOS) exists to make sure that required data eventually will be retransmitted in local area environments.

UDP See User Datagram Protocol (UDP) /.

UDP User Datagram Protocol:
the Internet Internet standard protocol for sending datagrams between user programs. This protocol neither guarantees delivery nor does it require a connection. As a result it is lightweight and efficient, but all error processing and retransmission must be taken care of by the application program. This protocol is built on top of IP and uses IP for datagram delivery (see TCP/IP TCP/IP). .

UDP:
User Datagram Protocol, defined by the IETF. This is a protocol used for communication across the Internet .

UFS See Unix File System (UFS) /.

UI See user interface (UI) /.

UI server The display manager and command/callback engine.

UI UNIX International:
a consortium including Sun and AT&T, promoting an open environment base on UNIX UNIX System V System-V including the Open Look Open-Look windowing system.

UID See user ID (UID) /.

UIL User Interface Language:
in OSF OSF/Motif Motif and DECwindows DECwindows, a language for specifying widget widget hierarchies etc.

UIMS User Interface Management System:
a system supporting the development and execution of user interfaces, usually on top of windowing systems.

UIMX
An interface builder for Motif Motif from Visual Edge.

UIS A VMS
VMS graphics programming interface package for VAXstations.

Ultrix
A version of UNIX UNIX based on the Berkeley version, designed and implemented by DEC to run on their VAX and DECstation DECstation series of processors.

UME UNI Management Entity:
The software residing in the ATM devices at each end of the UNI circuit that implements the management interface to the ATM network.

UML
Unified Modelling Language from Rational encompassing the object-oriented object-oriented analysis and design methodologies of Booch, Rumbaugh, and Jacobson.

UMS
Unfied Messaging Systems is a technology that should allow users to access messages sent in different formats through one single interface.

Unassigned Cells
A cell identified by a standardized virtual path identifier (VPI) and virtual channel identifier (VCI) value, which has been generated and does not carry information from an application using the ATM Layer service.

Undo
Back up one step; discard the most recent change.

UNI Ente Nazionale Italiano di Unificazione: the Italian national standards body, a member of ISO ISO.

UNI User-Network Interface:
An interface point between ATM end users and a private ATM switch, or between a private ATM switch and the public carrier ATM network; defined by physical and protocol specifications per ATM Forum UNI documents. The standard adopted by the ATM Forum to define connections between users or end stations and a local switch.

Unicast
When one individual, specific host sends a message to another individual, specific host. See also anycast /a, broadcast /b, multicast /m.

Unicasting The transmit operation of a single PDU by a source interface where the PDU reaches a single destination.

Uniform Resource Locator (URL)
Also called a Universal Resource Locator. The pointer that defines the access method, host, path name, and file name to some reference or resource on an internet, accessible via a WWW /w browser. Defined in RFC 1738 ftp://ftp.isi.edu/in-notes/rfc1738.txt and RFC 1808 ftp://ftp.isi.edu/in-notes/rfc1808.txt.

Uniformity
Comparison of one area's brightness to an adjacent area. In general, the brightest part of the image will be in the center area. When moving out to the edges, the intensity of image will vary in a non-linear function. This means that one comer of the screen will not be the same brightness as another comer of the screen. A typical CRT manufacturer's specification may call for up to a 30% difference between the center area and the corners.

Universal
Coordinated Time (UTC) The modern (post 1972) global coordinated time system, explained in fuller detail.

Universal naming convention (UNC)
A multivendor, multiplatform convention for identifying shared resources on network.

Unix
A multitasking operating system, created by AT&T’s Bell Labs, that is used trained on the Internet and accessible through most Web browsers.

UNIX - One of the most popular disk operating systems for the internet hosts.

Unix An operating system written by a couple of people at Bell Laboratories in 1972. They also wrote the C programming language. Since then, several variants of Unix have appeared, including BSD UNIX system V Unix, and Xenix.

UNIX Computer operating system developed by Bell Labs. Since it was written in C, it was possible to port it to run on different hardware architectures. It is now offered by many manufacturers and is the subject of an international standardisation effort. See also OSF OSF - . /UNIX

Unix File System (UFS)
The generic name for the modern implementations of the Berkeley fast file system (FFS) /f. A hierarchical file system /f in common use on Unix systems.

Unix international (UI)
A consortium of computer vendors that supports system V and gives guidance to USL.

UNIX
International A consortium of AT&T and others formed to advise on the development of UNIX UNIX System V System-V.

Unix System Laboratories (USL)
The organisation that develops and maintains Unix system V. Originally owned primarily by AT&T, it is now part of Novell.

Unix to Unix Copy (UUCP)
A file exchange protocol between two host computers. Used as part of many firewall mechanisms. See also firewall /f.

UNO Universal Network Objects.

Unshielded Twisted Pair (UTP) A cable where the pair of wires that carry the signal are not shielded from externalP electromagnetic interference.

Unsolicited Commercial Email (UCE)
Electronic junk mail advertising a product, service, or web site, where the recipient did not request to receive the message. See also spam /s.

UP
Unwired Planet is a set of technologies that enhances the number of services available for handheld devices, for example the UP-Browser.

UPC Usage Parameter Control:
Usage Parameter Control is defined as the set of actions taken by the network to monitor and control traffic, in terms of traffic offered and validity of the ATM connection, at the end-system access. Its main purpose is to protect network resources from malicious as well as unintentional misbehavior, which can affect the QoS of other already established connections, by detecting violations of negotiated parameters and taking appropriate actions.

Uplink Represents the connectivity from a border node to an upnode.

Upnode
The node that represents a border node's outside neighbor in the common peer group. The upnode must be a neighboring peer of one of the border node's ancestors.

URC Uniform (previously Universal) Resource Characteristic (Citation) - . /UR

URI Uniform (previously Universal) Resource Identifier - . /UR

URL
URL stands for "Uniform Resource Locator" or "Universal Resource Locator". It is a draft standard for specifying an object on the Internet, such as a file or newsgroup. The first part of the URL, before the colon, specifies the access method. The part of the URL after the colon is interpreted specific to the access method. In general, two slashes after the colon indicate a machine name (machine:port is also valid).example:

URL - Universal Resource Locator.
This is a Internet address which tells a user where to locate a specific Web HTML File. For example, Northern Web's EMALL, The Panhandle Pages resides at; http://www.northernwebs.com/ppages Other examples of URL's are;http://www.yahoo.com http://www.mcp.com/nrp/wwwyp/index.htm

URL
This is an acronym for Uniform Resource Locator. This is the address of the document that you want to look at. The URL for the Math department's home page is http://math.bu.edu. The first part of this (http:) says that the information you want to retrieve is on a web server. The math.bu.edu part gives the name of the Web server that the information you want to retrieve is located on.

URN Uniform (previously Universal) Resource Name - . /UR

Usenet
A very large, very informal, very disorganized network through which many megabytes of news, rumor, and gossip are distributed every day.

USENET
news A hierarchical organization of news articles and groups containing information. The information ranges from technical (comp.*) to entertainment and social activities (rec.*, soc.*) to debates (talk.*).

Usenet
The practice of using computer networks to exchange items of information grouped into "newsgroups" by topic. This is supported by a number of diverse and informally applied mechanisms and conventions - . /Usenet

USENIX
The UNIX UNIX and Advanced Computing Systems Professional and Technical Association

User Datagram Protocol (UDP)
A connectionless and therefore inherently unreliable data protocol (RFC 768) ftp://ftp.isi.edu/in-notes/rfc768.txt where data is sent but not acknowledged. No guarantee of delivery is defined in the UDP protocol; no attempt to recover from data loss is performed. See also IP family /i.

User ID (UID) A numeric value for the user's account identification.

User Interface (UI)
The interface between the user and the program. See also command line interface (CLI) /c, graphical user interface (GUI) /g, user /u.

User
The ultimate source or destination of a message, or the ultimate cause or effect of an action.

Username
The name by which Unix knows you. You enter this name when you log in. Also known as your user ID or login ID.

USL UNIX System Laboratories:
the software subsidiary of AT&T, responsible for UNIX UNIX System V System-V and related software.

USMARC See MARC MARC.

USSD:
Unstructured Supplementary Services Data allows for the transmission of information via a GSM network. Contrasting with SMS, it offers real time connection during a session. A USSD message can be upto 182 alphanumeric characters in length. This is a WAP bearer service.

UT Upper Tester:
The representation in ISO/IEC 9646 of the means of providing, during test execution, control and observation of the upper service boundary of the IUT, as defined by the chosen Abstract Test Method.

UTC See Universal Coordinated Time (UTC) /.

UTF UCS UCS Transformation Format of ISO ISO 10646.

UTF Universal Text Format an SGML SGML standard for the news distribution indistry - . /UTF

Utility A small, useful program. Unix comes with some utilities like diff and sort.

Utility An application, program, or script used to accomplish a specific task.

UTMS:
Universal Mobile Phone System is the European implemention of the ETSI’s 3G system. The advertised data rates for UTMS are: 144 Kb per second for vehicular transmissions, 384 Kb per second for oedestian and 2Mb per second for in-building communication,

UTOPIA
Universal Test & Operations Interface for ATM: Refers to an electrical interface between the TC and PMD sublayers of the PHY layer.

UTP See unshielded twisted pair (UTP) /.

UTP Unshielded Twisted Pair: A cable having one or more twisted pairs, but with no shield per pair.

UUCP See Unix to Unix Copy (UUCP) /.

UUCP The large international network of UNIX UNIX machines using the UUCP protocol to exchange news and electronic mail.

uucp The Unix-to-Unix copy program. One of the ways that mail, usenet news, and random files can be sent between computers.

Uuencoded file
An electronic-mail message format that contains a binary file disguised as text. When you run the message through uuencode, the binary file is reconstituted. This is a clever way to send binary files through electronic mail.

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