Fiber Optics Illustrated Dictionary - Part 98 pptx

UMTS technologies are characterized by high mo-bility and fleximo-bility in terms of available data rates and are considered suitable for wireless Internet ac-cess with global roaming ca

Fiber Optics Illustrated Dictionary

indicating a direction only, having a length

(magni-tude) of one (1 - unity) lUI=1.Thus, a vector may

be converted to a unit vector by dividing each

com-ponent of the vector by its magnitude See vector

United States Geological Survey USGS The USGS

carries out fundamental and applied research in

geo-logical surveying, cartographic data collection,

stor-age, search, retrieval, and manipulation It is

respon-sible for assessing natural ecological events, energy,

land, water, and mineral researches The USGS

con-ducts the National Mapping Program, and publishes

thousands of reports and maps each year

United States Telephone Association, United States

Telecom Association USTA An organization

founded in the 1800s which promotes the

well-be-ing of the industry, and provides technical and

stan-dards assistance, discussion forums, and publications

for its members USTA represents more than 1200

local exchange carriers (LECs)

USTA provides representation before Congress and

various regulatory bodies, training courses,

techni-cal bulletins, conferences, and media relations

USTA arose from the National Telephone

Associa-tion, established in 1897 This organizational strength

provided a voice for independents in the dominant

Bell marketplace The National Telephone

Associa-tion later became the United States Independent

Tele-phone Association (USITA) The Kingsbury

Commit-ment, an important step toward cooperation between

Bell and the Independents, entered into in 1913, may

have averted government takeover of the telephone

industry arising from charges of the monopolistic

control exerted by Bell at that time

After the mid-I 980s divestiture ofAT&T, USITA

be-came the United States Telephone Association

(USTA) and it is now known as the United States

Telecom Association to reflect the broader

technol-ogy base of local exchange carriers (LECs)

http://www.usta.org!

United Telephone Company Ahistoric phone

com-pany founded in 1898 by Cleyson 1 Brown in

Abilene, Kansas, and later expanded to other

com-munities.It operated there until 1966, and then moved

to Shawnee Mission, Kansas, where it forms the

lo-cal division of Sprint Corporation See Museum of

Independent Telephony

UNIVAC Universal Automatic Computer Ahistoric,

large, general-purpose electronic computing system

in active use in the 1950s, descended from the

ENIAC.It was designed and built in the mid-1940s

by the Eckert-Mauchly Electronic Control

Corpora-tion, but taken over before its completion by

Reming-ton-Rand UNIVAC was advertised as the UNIVAC

File-Computer "electronic brain" by Remington

Rand Univac, a Division of Sperry Rand

Corpora-tion UNIVAC was the first significant commercial

nonmilitary computing system, available for a little

more than $1 million

A mercury delay line, incorporating a long tube of

mercury, was installed inside the computer housing

as a memory device There were a number of input!

output modes, including magnetic tape, and various

peripherals, such as printers The clock speed of a UNIVAC wasn't much different from the personal computers first introduced in the mid-1970s and it took a great deal of care and expertise to get the sys-tem up and running and to maintain the vacuum tube-based hardware It was programmed wi th X-I

In spring, 1951, the U.S Census Bureau acquired an 8-ton UNIVAC system In 1952, the UNIVAC was used to (correctly) predict the presidential election re-turns but the results were not made public until after the election Due to the media exposure, UNIVAC became so well known that the name became a ge-neric tenn for large computing devices There is an original UNIVAC in the Smithsonian museum See ENlAC

Universal ADSL Working Group UAWG A

com-mercial consortium fonned to promote an easy-to-deploy, fast version of Digital Subscriber Line (xDSL) based on ANSI TI.413 Since traditional ADSL installations require a splitter to be wired to the subscribers' premises and a custom modem in-stalled in their computer, there have been a number

of initiatives to simplify the installation process and, hence, the cost, and to allow the subscribers a choice

of modem hardware See G.lite

universal asynchronous receiver-transmitter

UART UART chips and UART circuitry perform a conversion function within a computer When a com-puter software program generates data that travels from the computer to the serial card in a peripheral slot, or through a serial device to an external modem, the parallel data generated by the computer are con-verted by the UART into serial data that are then transmitted through the modem The same process oc-curs in reverse at the receiving end This is/lotthe same process as is performed by a pair of connected modems, which modulate and demodulate a signal, convert it from digitaltoanalog to transmit through the phone line and from analog to digital when re-ceived The UART does its job before modulation! demodulation occurs in the modem A UART chip may be in the computer, or in the modem itself

Universal Call Model UCM.In telecommunications

SS7 routing, an extension of the Basic Call Model associated with Intelligent Networks (INs) The UCM provides mediation between the Originating Call Model (OCM) and the Terminating Call Model (TCM) The UCM receives responses from an initial address message (lAM) and its associated calling line

ID, whereupon the UCM activates seizure of the originating channel.It then puts out a request for analysis ofthe A- and B-number and route and, when the information is received, looks up the dialed num-ber in a dialing base for routing During the call, the UCM maintains routing and bearer circuit status In systems using PRlISDN, the UCM is bypassed Also called line concentration module See Intelligent Networks Call Model, Virtual Switch Controller

Universal Digital Loop Carrier UDLC Digital

pub-lic switched network (PSN) carrier systems comprising a central office (CO) terminal near the switching system, a remote terminal at the customer's

premises, and a digital transmission link connecting

the two Functional criteria for digital loop carrier

sys-tems are described in Bellcore TR-NWT-000057

Digital switching streamlined the system, enabling

central office terminals to be integrated into the digital

switch

UDLCs were introduced in North America in the

early 1970s Connections to analog interfaces are

through twisted-pair copper wires, as are those

be-tween the remote terminal and the network interfaces

Universal Encoding Conversion Technology

UECT ADigital Equipment Corporation (DEC)

pro-prietary software system for converting documents

to and from Unicode UECT has been incorporated

into the AltaVista search engine, one of the

signifi-cant search tools on the Web from Digital Equipment

Corporation

universal mailboxA centralized computer point of

access for a variety of types of messages, including

email, digitally encoded voice messages, facsimiles,

etc., so the user can look at one listing to determine

what to read and when to read it and to simplify the

filing and cross-management ofdocument databases

See integrated messaging

Universal Mobile Telecommunications Systems

UMTS In conjunction with general packet radio

ser-vice (GPRS), UMTS encompasses next-generation

wireless telecommunications technologies UMTS is

a broadband, packet-based data transmissions

tech-nology base supported in Europe and also potentially

in Japan and other Asian countries.Itis not directly

compatible with emerging American mobile

stan-dards

UMTS technologies are characterized by high

mo-bility and fleximo-bility in terms of available data rates

and are considered suitable for wireless Internet

ac-cess with global roaming capabilities Since wireless

data technologies have lagged somewhat over the

years from lack of support and interoperability,

UMTS standards were developed to improve the

situ-ation and encourage market support for UMTS

de-ployment

UMTS standards were developed by two groups of

prominent telecommunications vendors Trials of

UMTS were carried out by Nortel Networks and

Brit-ish Telecom (BT) in 1999 In 2000, ETSI finalized

the first series of3GPP specifications into the UMTS

standard The UMTS first series specifies a wide

va-riety ofservices, including radio access, functions for

applications development, multimedia messaging,

and much more The Release 99 first series enables

developers to move ahead with the rollout of3G

ser-vices

As a result of standardization, companies such as

Nortel Networks have entered into agreements with

developers to create 3G wireless dual-mode modems

supporting the UMTS standard

Universal Mobile Telecommunications Systems

InitiativesUMTS Initiatives Third-generation

mo-bile telephony research and deployment efforts that

are being carried out by a number of companies in a

variety ofregions, but particularly in Western Europe

UMTS initiatives seek to support and foster the es-tablishment of broadbased UMTS standard-based wireless communications systems:

In May 2000, Lucent announced an initiative

to create a Bell Laboratories Research & De-velopment Centre to partner with Italian uni-versities to enable startup businesses and re-searchers to test ideas and products related to UMTS integration an implementation

• In November 2000, the German Bundestag (Parliament) approved UMTS funding for education and research to promote future de-velopment ofUMTS technologies

• In September 2001, Europolitan Vodafone an-nounced costs for their UMTS initiative in Sweden and a collaboration agreement with the Vodaphone Group

Universal Naming ConventionUNC 1 In general,

a convention for logically mapping a name to a pro-cess or device such that its explicit file path or rout-ing path is transparent to the user The UNC can be used to set up a virtual network with various print-ers, storage devices, scannprint-ers, etc linked in as re-sources regardless of where they may be located on the network 2 In terms of file storage, a convention for identifying a shared file on a computer network without explicitly identifying its storage location to the user This increases ease of access and transpar-ency to users who shouldn't have to worry about the location of a file on a virtual storage system (which may be a device on another machine a few feet or a few thousand miles away) except as desired Universal Payment PreambleUPP An electronic commerce payment mechanism developed by JEPI, based on work by Don Eastlake The mechanism was described through an RFC document including sev-eral examples in August 1996 as to its relationship between the HTTP Payment Extension Protocol (PEP) UPP provides a uniform vocabulary for a uni-form syntax and naming options common to payment systems Common parameters could be specified within PEP-specified header fields and in payment-system-specific headers See JEPI, Payment Exten-sion Protocol

universal payphoneA payphone with a wide scope ofpayment options including coin, calling card, credit card, collect, etc

Universal Serial BusUSB.Anopen serial data bus standard developed by a consortium of prominent computer products and telecommunications services providers in the mid-1990s.Itallows peripherals to

be attached to a computer through a single periph-eral attached to the motherboard, with other devices chaining or attached in a star topology Commercial USBs are designed to support many devices, some-times up to 64 (the host computer is considered a de-vice) AUSB will sometimes also provide additional power to devices that might require it One of the basic goals of USB development was ease of use It was intended for personal computer users to be able

to easily attach and detach external computer

Fiber Optics Illustrated Dictionary

peripherals without a lot oftechnical expertise Thus,

characteristics such as hot swapping and the

capabil-ity to attach multiple devices were desirable design

goals Through a process of enumeration, peripherals

are assigned unique addresses for managing runtime

data transmissions and transactions

The Human Interface Device (HID) Class is a USB

Core-compliant aspect ofUSB intended for user

in-put devices that require relatively slow data rates (1.5

MBytes/sec) compared to high-speed storage access,

audio/visual, or networking transmissions (12

MBytes/sec) RIDs include keyboards, mice,

joy-sticks, graphics tablets, etc Traditionally the USB

RID Class is connected to the computer through a

wire, but interest in wireless versions is strong and

implementations are being suggested

The format is rapidly gaining popularity and many

personal computers now come with USB ports built

in Older computers with PCI slots can be adapted

for use with USB through peripheral cards.Itis

com-mon for a peripheral card to have two USB ports

With the success ofUSB 1.1, work continued on USB

2.0 to give it even better performance characteristics

Itis estimated that higher data rates ofmore than 400

MBytes/sec may be possible without substantial

hard-ware changes (with the exception of hubs) through

the use of microframes Transmission speeds for a

variety of attached devices would be individually

negotiated, providing backward compatibility and

flexibility in device data rates See FireWire

Universal Service Order CodeUSOc.An

identifi-cation system for tariff services and equipment

in-troduced in the 1970s by AT&T, and later adopted by

the Federal Communications Commission (FCC)

Since divestiture, the code is even less universal than

before, with individual Bell operating companies

de-veloping billing systems somewhat independently of

one another

Universal TimeSee Coordinated Universal Time

Universal Transverse Mercator projectionUTM

A map projection technique that preserves angular

re-lationships and scale UTMs are used in many

plani-metric and topographic maps A UTM consists of a

series of identical projections, each 6° of longitude

oriented to a meridian, taken from around the world's

mid-latitudes

Universal Unique IdentifierUUID Aunique

iden-tifier originating from the Network Computing

Sys-tem (NCS) and the Open Software Foundation (OSF)

distributed computing environment In February

1998, Leach and Salz defined the format ofUUIDs

guaranteed or extremely likely to be different from

all UUIDs generated until the year 3400 A.D.,

de-pending upon the mechanism chosen for generating

theUUID

In a data communications equipment (DCE)

trans-missions cell, it is a broadly unique 128-bit

identi-fier assigned to an object The UUID is typically used

in global contexts where it is a challenge to assign a

guaranteed unique ID Thus, a combination of data

are combined to produce the UUID, which may

in-clude time stamps, random quantities (or seeds for

random quantities), and the hardware address of the originating network device, etc

In the context ofUniversal Resource Identifier(URI) schemes on the Internet, a UUID enables network resources to be uniquely named without regard to lo-cation; they are thus not tied to a physical root name-space These are also known as Globally Unique Iden-tifiers (GUIDs) UUIDs are useful in that they need not be assigned and administered by a centralized authority (beyond node identifiers), as are domain names They also have potential as transaction IDs,

a property ofparticular interest to e-commerce trans-actions

In Unix applications, theUuid class provides a means

for creating and convertingUuid objects to support

network UUIDs

Universal Wireless Communications UWC A wireless communications collaborative program ini-tiated by wireless operators and vendors in 1995 The program is built on the TIA IS-136 Time Division Multiple Access (TDMA) radio frequency standards, along with IS-41 Wireless Intelligent Network(WIN) standards

Universal Wireless Communications Consortium

UWCC AWashington State LLC, established to sup-port carriers and vendors ofIS-136 TDMA/IS-41 WIN standards The UWCC sponsors a number of working forums, including the Global TDMAForum (GTF), the Global WIN Forum (GWF), and the Glo-bal Operators Forum (GOF) See Universal Wireless Communications http://www.uwcc.org/

UnixAwidespread, powerful operating system, origi-nally developed in 1969 by Ken Thompson at AT&T Bell Laboratories The trademarked version ofUnix

is spelled all in caps as UNIX, whereas Unix spelled

in upper and lower case is used generically in the computer industry to refer to the many freely distrib-utable flavors of Unix that have been implemented

by different groups UNIX has gone through a num-ber of hands, from AT&T, to Novell Inc., to the X/ Open Company Limited See UNIX

UNIXUNIX is a powerful, widespread, cross-plat-form, Internet-friendly, multitasking, multiuser op-erating system When spelled in all capitals, UNIX

is a registered trademark, licensed exclusively through the X/Open Company Limited See Single UNIX Specification, Unix

UNIX Computing ForumUCF A comments and feedback forum through the Santa Cruz Operation, Inc (SCO), which provides UNIX server operating systems and related products

Unlicensed Personal Communications Services, Unlicensed PCS UPCS A number of low-range communications systems can be used without broad-cast licensing These are commonly used for appli-cations such as cordless phones, intercoms, monitors, etc Some are incorporated into short-range wireless local area network (LAN) data and phone systems Specific frequency ranges have been assigned to UPCS services by the Federal Communications System (FCC) UPCS are permitted within the 1890

to 1930 MHz frequency ranges and are further

subdivided for use with asynchronous (1910 to 1920

MHz)and isochronous (1890 to 1910 and 1920 to

1930 MHz) communications See band allocations

unlisted phone numberA service requiring a fee,

in which a phone listing is not published in printed

directories or available through directory assistance

Some carriers also provide unpublished service,

which is excluded from printed directories, but may

be listed with directory assistance, as a partial privacy

measure People pay to prevent their numbers from

being listed for a variety of reasons: to avoid crank

calls, undesired telephone solicitations, harassment

from ex-spouses, etc Some carriers make it possible

for callers to leave a message for an unlisted

num-ber, which the caller mayor may not return at his or

her option This is useful for emergency calls See

un-published phone number

unmatched callA call that does not have a

corre-sponding match in a Service User Table(sur).Call

matching is a way of determining whether the call is

authorized and should be pennitted to ring through

If there is no match to the destination number in any

of the relevant lookup tables, such as the

Authoriza-tion Code Table (ACT) or Calling Card Table, the

card will likely be rejected or may be redirected to

someone in authority

unpublished phone numberA service, usually

re-quiring a fee,inwhich a phone listing is not published

in printed directories, but mayor may not

(depend-ing upon the carrier) be available through directory

assistance Thus, if listed with directory assistance,

it is a midway solution between a listed and an

un-listed number Some people choose unpublished

phone numbers to avoid crank calls and undesired

telephone solicitations Some carriers will

subscrib-ers to exclude addresses from a published listing,

without charging extra For further privacy, see

un-listed phone number

unshieldedUnprotected from emitting or receiving

electromagnetic interference or broadcast signal

in-terference Most cables are shielded with plastic and!

or metal foil, but since this increases the weight and

cost of the cable, there are still circumstances where

low shielded or unshielded cables are used In video

applications, well-shielded cables are recommended

Monitors should be shielded to protect users from

radiation exposure, and computers shielded to

pre-vent interference with nearby broadcast devices, such

as radios Improper or insufficient shielding may

re-sult in Federal Communications Commission (FCC)

rejection in the manufacture of new products

unshielded twisted-pairUTP A very common type

of cable consisting of one or more pairs of twisted

copper wires bound together UTP is frequently used

for phone wire installations intended to carry faster

data rates See twisted-pair cable

Unsolicited Commercial Electronic Mail Act of

2001 Abill proposed by Rep Heather Wilson in

Feb-ruary2001 to protect Internet users and providers

from unsolicited and unwanted electronic mail

Between 1995 and the present, the volume and

fre-quency ofunsolicited electronic mail, also known as

"spam," rose dramatically, resulting in significant load to service providers along with lost productiv-ity and undesired costs to users who had to filter out the messages and sift through them to locate legiti-mate mail Because the cost to the sender ofsending email is often insignificant, "junk" email is a far greater problem than junk postal mail The cost of sending out a million junk postal solicitations is typi-cally more than $30,000, providing an economic de-terrent to excessive mailings In contrast, the cost of sending out a million email messages may only cost pennies to the sender but may result in significant for-warding, storing, and filtering costs to service pro-viders and recipients, especially as junk email file sizes increase due to added images and HTML-for-mat tags

Junk email is now widely used to promote fraudu-lent money-making schemes, off-shore sheltering of illegal gains, young teen pornography, black market pharmaceuticals, and gray market consumer items Thus, many feel that stronger legislative constraints

on unsolicited electronic mail should be put in place

to protect recipients and providers from bearing the cost and inconvenience of these solicitations unspecified bit rateUBR.Anunguaranteed ATM networking service type in which the network makes

a best-effort attempt to meet the sender's bandwidth requirements See available bit rate, cell rate unsupervised transfer, blind transferAphone call transfer in which the recipient is not advised as to the identity of the caller This is common on automated systems in which the caller can select an extension

by way of the keypad on a touchtone phone

unusedA product which may have been opened, or taken home and returned, but which has not been used.Itmay have slight abrasions and, if sold, may carry a warranty that differs from a new warranty UPC Usage Parameter Control A network mecha-nism for monitoring and controlling traffic and guar-anteeing service for legitimate uses See traffic po-licing, traffic shaping

UPCS See Unlicensed Personal Communications Services, Unlicensed PCS

UPGRADEAnACTS project intended to increase the capacity of the existing single fiber European Communications network to higher bit rates over existing hardware to serve the needs of future com-munications Capacity will in part be increased with new modulators, switches, and semiconductor laser amplifiers Various European networks (Deutsche Telekom, 1998 EXPO in Spain, etc.) are involved in testing the systems Test results and components from the project will be used to update single fiber links

to ca 1300-nm wavelength See BLISS, BROAD-BAND, and WOTAN

uplinkInbroadcast communications, the uplink is the leg from an Earth station to a satellite From the satellite back to the Earth is a downlink The dis-tinction is made partly because of the different technologies used in satellite and Earth stations, but also because uplink and downlink services can often

be purchased separately

Fiber Optics Illustrated DictionanJ

upload, send, transfer To transmit a broadcast or

transfer data from the current device to another one,

usually at a different location or desk Computer data

are often uploaded from a personal computer to the

Internet or to a mainframe Information from a

lap-top may be uploaded to a desk computer

Telecom-munications software, Web browsers, and FTP are

common waysinwhich people upload files

Broad-casts may be uploaded to a satellite link See

up-stream Contrast with download

Ground-Air Data Transfer

The uplink is the transmissions path fiom the Earth

to the satellite, which is often at a different frequency

from the downlink in order to reduce ill/erference

be-tween incoming and outgoing signals.

upp See Universal Payment Preamble

upper layer protocol ULP In hierarchical network

models, a protocol that operates at a higher level of

the model, which usually consists of appl ication and

user transactional functions In the Open Systems

Interconnection (OSI) reference model, ULP more

speci fically refers to protocols in any of the layers

higher than the layer currently being referenced,

al-though colloquially it often means the next higher

layer

upper memory area UMA Asection ofmemory on

Intel-based IBM and licensed third-party computers

commonly used to buffer video data which can be

ac-cessed and read by a video graphics display card

upstream Generally, the transmission going in a

di-rection away from the reference point Thus, the

stream of data from a personal computer to a

main-frame would be considered upstream Sometimes the

designation implies from a smaller or less powerful

system to a larger or more powerful system, so its use

is not completely standardized In cable networks, the

transmission from the transmitting station to the cable

television headend is the upstream direction See

up-load Contrast with downstream

uptimeAnuninterrupted interval during which a

sys-tem or process has been in active service The active,

functional time between failure or maintenance

pe-riods Contrast with downtime

upwardly compatible Adevice or program intended

to work with later upgrades or revisions Upwardly

compatible may also mean compatible with a larger

or more complex version For example, a handheld device bar code device may be designed to be up-wardly compatible with a desktop computer Upward compatibility in terms oflater versions is much more difficult to achieve than downward compatibility, since future changes or improvements cannot always

be anticipated Contrast with downwardly compatible URA See Uniform Resource Agent

URI See Uniform Resource Identifier, URL, URN, RFC 1630, RFC 1738, RFC 1808

URL See Uniform Resource Locators See RFC 1738

URN Uniform Resource Name See RFC 1737 U.S West One of the regional companies created when AT&T was divested in the mid-l 980s, compris-ing Mountain Telephone, Pacific Northwest Bell, Northwestern Bell, and other related firms servicing the "Fourth Comer."

USB See Universal Serial Bus

USDC U.S Digital Cellular A telephone standard which uses frequency division multiple access (FDMA) and time division multiple access (TDMA) techniques in the 824 to 894MHzrange

USDLA United States Distance Learning Associa-tion See distance learning

USDN U.S ISDN services See ISDN

used A term describing a product that has been opened and used, with no implications astothe qual-ity, age, or remaining useful life of the product Used equipment is generally represented as being in work-ing condition, as far as is known See certified, fair, like new, refurbished

USENET Created in late 1979, shortly after the re-lease ofa Unix V7 which supported UUCP, USENET

is an important communications medium best known for its more than 35,000 public newsgroups USENET was developed by Tom Truscott and Jim Ellis at Duke University, and Steve Bellovin at the University of North Carolina The first two-site in-stallation was described in January 1980, at the Usenix conference and, after modifications by Steve Daniel and Tom Truscott, it became known as A News

As soon as it caught on, A News volume began to steadily increase In 1981 Mark Horton, from UC Berkeley, and Matt Glickman enhanced the software

to better handle the increasing volume of informa-tion This 1982 version was known as B News Two years later, administration of the software was taken over by Rick Adams from the Center for Seis-mic Studies Moderated groups capability was added,

in addition to compression, a new naming structure, and control messages Arewrite by GeoffCollyer and Henry Spencer of the University of Toronto was re-leased as C News in 1987

In 1992, Rich Salz released lnterNetNews(INN),a program optimized for NNTP hosts, but with support for UUCP INN was designed for socket-oriented Unix hosts Enhancements and bug fixes to INN were released by David Barr, beginning in 1995 Maintenance of INN was taken over by the Internet

Software Consortium.

UUCP gave way toTCP/IP, and TCP/IP's greater

compatibility across platforms was a means to

pro-vide wider access to newsgroups The Network News

Transfer Protocol (NNTP) was also developed and,

in 1986, a means to use this for news articles was

re-leased For more information, see the "USENET

Soft-ware: History and Sources FAQ" on the Internet See

FidoNet, newsgroup, RFC 822, RFC 1123, RFC 977,

RFC I036,RFC 1153

userSometimes called end were Although often used

to indicate a nontechnical consumer of a product or

service, a user also generically refers to anyone

in-teracting with that product or service, as opposed to

developing or distributing it

user acceptance testing, user application testing

UAT The testing of a product by actual users (those

who fit the profile of potential buyers or users) in

conditions similar to what the use environment would

be in order to ensure acceptance of the product and

sufficient design ergonomics and explanation (menus,

manuals, etc.) for the operator to be able to use the

product without significant intervention or assistance

VAT occurs when the product is considered to be

fin-ished and in good working order (bug-free) This is

an extremely important aspect of product

develop-ment, as many entrepreneurs have "surefire" ideas not

readily appreciated or desired by users (e.g.,

potato-flavored ice; yes, someone actually tried it) This can

also be referred to as delta testing or enduser testing

See beta testing, gamma testing

user accountAn account assigned for a specific

in-dividual on a computer network or on a multiuser

machine Auser account is a security system

config-ured by the system administrator The sophistication

ofthe security can range from a simple name prompt

at the time of login, to name and password logins at

various levels of access, and different protections

attached to directories, processes, and programs User AgentVA A network service used by clients

to find available services on behalf of the user See Directory Agent, Service Agent, Service Location Protocol

User Datagram ProtocolUDP An IETF-recom-mended protocol for the Internet which provides a datagram mode for Internet Protocol-based (IP-based) packet-switched network communications UDP is primarily used with the Internet Name Server and Trivial File Transfer The format ofUDP header

is shown in the User Datagram Protocol Header chart For more details about UDP, see See RFC 768 user eventIn programming, a type of input event which is signaled through an input device such as a mouse, joystick, keyboard, or touchscreen, and inter-preted into a response by the operating system or ap-plications program User events typically include button, window, or menu selectionsladjustments and movement of icons, windows, or objects The most challenging types ofuser events tend to occur in fast action video games and realtime graphics input pro-cessing

User Glossary Working GroupUGWG A group within the User Services Area of the Internet Engi-neering Task Force (IETF) which has created an In-ternet Users' Glossary See RFC 1392

user group, user's group, users' groupAn organi-zation of users of a particular product or service A support group With the introduction of computers, society took a technological leap that was difficult for anyone individual to understand or bridge In or-der to facilitate the use and unor-derstanding of com-plex systems, programming languages, and technolo-gies, many users' groups sprang to life, beginning in the mid-1950s, to provide mutual support and assis-tance in sharing information and meeting technologi-cal challenges

User Datagram Protocol (UDP) Header Format

0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 789 012 345 6 7 8 901 + -+ -+ -+ -+

+ -+ -+ -+ -+

+ -+ -+ -+ -+

+ -/

Source Port

Destination Port

Length

Optional Indicates sending port The default port for replies, zero if not used

Related to specified Internet destination address User datagram length in octets, including the header and data The minimum is eight

Fiber Optics Illustrated Dictionary

The proliferation of users' groups is important not

only for the support they provided to members, but

also because this venue provided a forum for

com-puter hobbyists, amateur radio groups, and many

other amateur and professional enthusiasts to

brain-storm ideas and contribute to the developing fields

The development of computer technology was no

longer in the hands of large educational institutions

and corporations Individuals and small companies,

particularly in the 1970s, had a window of

opportu-nity during which they were able to make highly

sig-nificant contributions to the development of the

in-dustry

user interface ill The communications link through

which a person interacts with a machine On

com-puters, the ill, in its broadest sense, includes the

vari-ous symbolic text, images, sound, and other sensory

cues and gadgets presented to the user, with which

the user interacts This is commonly done through

pe-ripheral devices such as touchscreens, keyboards,

mice, joysticks, microphones, data gloves, and

oth-ers not yet invented.Itis considered the highest layer

of the computer system structure, with the machine

instructions for physical operations comprising the

lowest layer

The user interface is the single most important aspect

ofcomputing and should never be undervalued

Com-puters were designed to serve the needs ofpeople; if

people are forced to adopt unhealthy or

uncomfort-able habits to interact with computers, or if

comput-ers take time away from people rather than freeing

them from repetitive tasks or drudgery, then human

needs are not adequately served by the technology

User interfaces and software applications should be

designed with the goal that the purpose of the

tech-nology is to improve the quality oflife

The design of user interfaces is an art.Itdemands

common sense, a knowledge of ergonomics,

psychol-ogy, philosophy, electronics, aesthetics, and a large

dose of sympathy for a broad range ofusers As such,

user interfaces have developed in fits and starts, with

many software programs providing very poor support

for users, forcing the user to conform to the

idiosyn-crasies of the machine (or the programmer who wrote

the software), rather than the other way around See

user interface history

user interface history The earliest

telecommunica-tions interfaces consisted of physical semaphores

(smoke, flags, and arms) and telegraph keys sending

coded messages that needed to be decoded and

tran-scribed when received The received message was

usually presented as a long paper tape inscribed with

wiggly lines, dots and dashes, or punched holes

Computers up until the 1950s used a similar model

This kind of user interface wasn't very friendly, so

inventors, even in the earliest days of

telecommuni-cations technology, sought ways to encode the

alpha-bet, so that letters could be directly sent and received

(eventually resulting in teletypewriters) without the

operators doing the translation But the basic

meth-ods prevailed for decades, mainly because they could

be used anywhere, with the simplest of equipment

Telegraph key codes are still a requirement of attain-ing amateur radio licenses

With the development of personal computers, user interfaces took a leap The Altair microcomputer, sold originally as a hobby kit in 1984, had no monitor, mouse, or keyboard Itwas programmed by means

of flipping little dip switches; ifyou made a mistake, you had to start again Yet within 2 years modem microcomputers, inspired partly by high-end systems with better resources than the Altair, came into be-ing in the form of the TRS-80 and Apple computer, and keyboards and monitors became standard Al-most every change since then has been an evolution-ary refinement or logical addition rather than a revo-lutionary change Even the lifelike and startling three-dimensional virtual reality world represents, for the most part, an evolutionary development, albeit an exciting one

Early computer user interfaces consisted primarily of monochrome screens displaying limited text, often with no lowercase letters, and large rectangular graphic blocks While ingenious computing pioneers wrung astonishing surprises from this primitive tech-nology, it was obvious that improvements were needed in order for a computer to be more fun, ver-satile, and consumer-friendly

User-to-User Indicator UUI In ATM network Ad-aptation Layer 2 (AAL2), a 5-bit indicator in a 3-oc-tet-header CPS packet that follows the length indi-cator (LI) and precedes the header error control (HEC) Initially the PPT and UUI were separate fields, but were merged in the mid-1990s into one field, sometimes called the CPS-UUI field The UUI field enables upper layers (users) to somewhat trans-parently convey parameters, for example

UserID User Identification A unique computer ac-count designation used to gain access to a secure or monitored system AUserID is frequently paired with

a password for system access Historically many sys-tems accepted only eight characters for the UserID and, for backward compatibility, this limitation per-sists on many systems today On networks using the most common mail systems, the UserID typically forms the first part of an email address

USGS See United States Geological Survey USITA Formerly United States Independent Tele-phone Association See United States TeleTele-phone As-sociation

USKA Union Schweizerischer Kurzwellen-Amateure Union (Union of Swiss Shortwave Ama-teurs) Amember organization associated with the In-ternational Amateur Radio Union

http://www.uska.ch/

USOC See Universal Service Order Code

USOP User Service Order Profile

USPIX The USOC code for telephony-related main-tenance plan, standard, levell, per line/circuit, UN! USTA See United States Telephone Association UTI A time reference based upon Earth's axis rota-tion It is related to Coordinated Universal Time in that UTC was set to synchronize with UTI at 0000 hours on January 1, 1958

UTAMSince some ofthe frequencies used by

incum-bent carriers have now been designated for USDC

services (1890 to 1930 MHz), companies are

chang-ing their operatchang-ing equipment and software to

oper-ate instead in the 2.0 GHz microwave C-band UTAM

Inc is an open industry resource for assisting in

fre-quency relocation See band allocations

UTCSee Coordinated Universal Time

UTDRUniversal Trunk Data Record

Utility Communications Architecture UCA A

comprehensive suite of communications protocols

based upon open systems for use by electric utilities

providers/maintainers UCA began at the Electric

Power Research Institute (EPRI), in 1988 UCA is a

flexible, scalable architecture that can control

vari-ous types ofdevices ranging from small local devices

to those in major installations and control centers

UCA Version 2 has been developed to support the

communication needs of Energy Management

tems, Supervisory Control and Data Acquisition

Sys-tems, Intelligent Electronic Devices, Remote

Tenni-nal Units, and others The standardization effort is

intended to help utilities providers to

intercommuni-cate through a variety of physical media, to reduce

installation, operations, and migration costs, and to

achieve secure communications through standard

mechanisms

UCA documents are being assessed by an IEEE

Stan-dards Coordinating Committee for review as

poten-tial IEEE standards

Utility Communications Architecture Forum UCA

Forum A group dedicated to promoting UCA and

assisting individuals and companies in

understand-ing, utilizunderstand-ing, and furthering this technology

http://www.ucaforum.org/

utility pole Asturdy tall pole installed in the ground

(or on the ground in mountainous areas, supported

by rocks and guy wires) The pole is used to support

utility wires for power and telecommunications and

may have crossbars and insulators Utility poles are

raised with the aid of long poles with spikes on the

end called pike poles, or with industrial machines

designed for the job Most poles are made from logs,

although some areas have metal poles; at one time in

history, it was thought that metal poles would soon

replace all the wooden poles, a prediction that didn't

hold true In some areas, especially avalanche areas,

it was necessary to reinstall poles once or twice a year,

a costly, time-consuming business, so various

alter-natives were tried, including laying the wire along

the ground Unfortunately, rodents like to chew

through the wires, causing almost as much

interrup-tion to service as the avalanches Transmissions in

inclement regions are now often sent with microwave

transceiving systems rather than with wires, a

solu-tion which requires less maintenance See joint pole

for more details and diagrams

See Universal Transverse Mercator Projection

UTMuuepMap A logical map describing the

in-terconnections between intercommunicating

UUCP-capable systems AUUCP Map Entry is issued when

a host is registered on the UUCP system The main

routing infonnation in UUCP-base networks is

re-lated to the UUCP Map and is contained in apathalias database Thus, for a message from mysite.org to be delivered to yoursite the path might be expressed as

mysite.org sitel!site2!midsite3!yoursite!%s Because exclamation marks are traditionally used to separate the nodes, this is commonly called a "bang path" and veterans ofthe early email days can remem-ber typing bang paths into their emailTO.'headers

In the early 1980s, the UUCP Map was still small enough to be represented on a single page, with

sys-tems such as ucbvax, menlo70, decvax, and chico

rep-resenting familiar interlinks to those who were us-ing the system at the time From this point, UUCP grew and spread to the point where static connections/ routing maps were no longer practical in the way they were in the early UUCP days By the 1990s, map updates generally came from domain registrations rather than from manually submitted registrations By

2001, it was announced that UUCP Maps would likely be replaced with XML for future registrations There are sites on the Web that enable the UUCP Map

to be queried for a specific entry For example, a

search for ucbvax lists the Internet mail routing

en-tryas cs.purdue.edu!ucbvax!roS and the UUNET mail

routing entry as decwrl.dec.com!decvax!purdue!ucbvax!%s The UUCP Map can also provide infonnation about site administrators In Europe, UUCP Map entries are available through the backbone "netdir" selVice Joint Utility Pole With a Variety of Cables

A typical utility pole with crossarms bearing pri-mary power lines, ceramic insulators, below which are transformers in cylindrical containers feeding power to secondary power lines, and local power drops to nearby residences and businesses Below these are the telecommunications cables carrying voice and data services.

Fiber Optics Illustrated Dictionary

UTPSee unshielded twisted-pair

UTRUniversal Tone Receiver

UTSUniversal Telephone Service

uuepUNIX-to-UNIX Copy UUCP was a basic

networking system developed in the mid-1970s by

AT&T Bell Laboratories; it was distributed with

UNIX in 1977 UUCP was quickly adopted by many

educational and research institutions for

disseminat-ing mail Two years later USENET, the global

pub-lic news forum, was established using UUCP

As UUCP spread and became an important medium

for computer connectivity, it was ported to many other

computer architectures In 1997, UUCP mail routing

was taken over by the UUCP Project By the

mid-1980s national networks in other countries were

be-ing set up with UUCP, establishbe-ing it as an

impor-tant catalyst for intercommunications and the

devel-opment of distributed networks Due to its

increas-ing importance, formats for the transmission

ofelec-tronic mail through UUCP were then standardized for

mixed computer environments along lines developed

by ARPA.In 1987, UUNET was founded to provide

commercial UUCP and USENET access See

BITNET, Unix, UNIX, USENET, UUCP Project,

UUNET, RFC 822, RFC 920, RFC 976

uuepProject Aproject initiatedinthe early 1980s

to enable the exchange ofelectronic mail among

com-municating sites using the UUCP store-and-fOlWard

transport system The UUCP Mapping Project

en-deavored to create a single worldwide database of

systems interconnected through UUCP, in addition

to the determination of optimum data paths between

systems In 1997, the UUCP mail routing for UUNET

site, created by Eric Ziegast, was turned over to the

UUCP Project currently coordinated by Stan Barber.

SeeUUCP

http://www.uucp.org/

urn1 See Unified User Interface 2 See unique user identifier 3 See User-to-User Indicator

UUInSee Universal Unique Identifier

UUNETA Unix-based network provider and back-bone (long-haul network) UUNET provides Internet name serving, connectivity, MX forwarding, and news feeds The formation ofUUNET was probably due in part to the Acceptable Use Policy (AUP) fo-cus on research and education enforced by the Na-tional Science Foundation's NSFNET This stimu-lated commercial establishment of computer net-works

In the 1980s, UUCP over long-distance dialup lines was the primary means by which providers, institutions, and individuals received their messages However, Internet connectivity has become ubiquitous and the situation has changed In the 1990s, UUNET is the only remaining significant network that uses UUCP transport for USENET messages UUNET Canada, Inc is located in Toronto; UUNET Technologies Inc

is located in Virginia

URN See Uniform Resource Name

UV See ultraviolet

UWB ultra wideband

uweSee Universal Wireless Communications

uweeSee Universal Wireless Communications Consortium

UXTxxThe USOC code for telephony-related sur-charges for emergency reporting services Thexx

designates the region For example, UXTMN refers

to UXT services for Minnesota

v1.symb.volt (may also be capitalized) See volt.

V 1 symb vacuum tube See Audion, electron tube,

vacuum tube 2 symb voltmeter.

V&HCoordinates,V HCoordinatesVertical &

Horizontal grid coordinates Imaginary coordinate

points on a virtual grid used to determine

straight-line mileage between two specified points, with each

exchange's location represented by a pair of V & H

coordinates This is used for various products and

services charged on a distance or mileage basis, as

are long distance calls

The V & H system is based upon a 'flattened Earth'

system from a Donald Elliptical Projection,

devel-oped by Jay Donald ofAT&T in the mid-1950s The

basic idea is to create a triangular distance

calcula-tion over a flattened surface

V& HTapeVertical and Horizontal Coordinates

Tape A recorded tape provided primarily to assist

with billing, it includes NXX types, major and

mi-nor V & H coordinates (latitude- and longitude-like

regional designations), LATA Codes, and other

infor-mation related to long distance accounting and

ser-vice areas It can be purchased from Bellcore

VdriveInanalog video, a periodic signal related to

the vertical component ofa frame that is constructed

with sequential, repeating line scans In standard

sys-tems, the V drive sends a pulse so that the electron

gun returns from the bottom right comer ofthe video

frame to the top left comer (during the vertical

blank-ing interval) in order in position for imagblank-ing the next

frame (or half-frame in an interlaced system)

The horizontal and vertical sync are related so that

pulses can be combined on a single wire, together

comprising a composite video signal A composite

signal can be represented as Csync-red-green-blue

and transmitted over four wires

Many computer monitors use a five-wire RGBHV

system in which the H and Vrepresent horizontal and

vertical sync pulse components See H drive,

nega-tive-going video

VinterfaceInISDN, a number of reference points

have been specified asR,S, T, U, and V interfaces

To establish ISDN services, the telephone company

typically has to install a number of devices to create

the all-digital circuit connection necessary to send and

receive digital voice and data transmissions

The V interface is the reference point between the telephone switching office's exchange terminal switch and the line terminal switch Thus, one side connects to the public telephone exchange and the other connects through the U interface to the subscriber's network termination(NTx)device See ISDN interfaces for a diagram

Vnumber(symb -v)Infiber optic lightguides, the

normalized frequency parameterfor describing the number of modes in a given fiber optic waveguide The transmission ofdifferent guided or radiant modes

in a fiber is based upon the materials used and their respective refractive indexes, the core diameter, and the relationship of the core to the reflective cladding that surrounds it

Mathematically, the V number can be expressed as 21t (which is the number of radians in a full circle) times the radius of the fiber core (in microns) which yields the circumference of the core This is divided

by the wavelength (in microns) times the numerical

aperture of the fiber (square root n 2

J- n 2i)where the numerical aperture (NA) is derived ttom tne core(nJ)

and cladding(n2)relationship Symbolically, the V number may be expressed asV=(21ta/l)NA Smaller V numbers tend to be associated with single-mode fiber transmissions, while larger Vnumbers are associated with multimode fibers that can transmit more than one wavelength Within multimode fibers,

a larger V number is associated with a larger numeri-cal aperture up to practinumeri-cal tolerances

The V number provides information that is useful in determining relationships between core and cladding relative to (1) the wavelengths that are intended for use with a particular cable and (2) the beam width of the illumination source for the lightguide See clad-ding, dominant mode, index ofrefraction, numerical aperture

VSeries RecommendationsA set ofITU-T recom-mended guidelines for interconnecting networks and network devices These are widely implemented in computer modems The V Series specifications are available for purchase from the ITU-T, and a few may

be downloadable from the Net Some of the related general categories and specific V category recom-mendations of particular interest are listed here See also I,Q,and X Series Recommendations