Fiber Optics Illustrated Dictionary - Part 97 doc

Type of Service is both a ge-neric concept in networking and a specific parameter related to Internet Protocol communications.. Auxiliary products and accessories intended for use with a

Fiber Optics Illustrated Dictionary

Type of ServiceToS Type of Service is both a

ge-neric concept in networking and a specific parameter

related to Internet Protocol communications It

de-scribes and determines various networking

param-eters related to speed, security, format, etc As with

many types of network services, there may be

trade-offs between speed, flexibility, and security,

depend-ing upon how ToS is specified at any particular time

or on specific types of networks ToS is now

man-dated by the Requirements for Internet Hosts

speci-fications described in the various relevant Requests

for Comments (RFC) documents At the present time,

support for ToS is somewhat uneven and there are

known problems on some prevalent systems

In Internet Protocol (IP), a byte in the IP header

sup-ports Type ofService information The byte is divided

into the precedence field, the lOS field, and a

re-served bit, only one of which may be set at a time It

is recommended that routers be cognizant of the ToS

value for a route in the routing table If the routing

protocol does not support ToS header settings, the ToS

must be assigned the default value of zero (0)

Physical Link Security Type of Service was described

as an RFC by D Eastlake in May 1993 It was

sub-mitted as an experimental protocol providing a ToS

to request maximum physical link security in addi-tion to existing types of services in the Internet Pro-tocol (IP) Suite This ToS requests protection against surreptitious observation by agents labeled as outside the traffic

When transporting SNA network traffic over TCPIIP networks, there are issues with preserving the SNA Class of Service (CoS) parameters Cisco addressed this issue by developing a data-link switching en-hancement (DLSw+) to improve response time and the effective use ofbandwidth while supporting SNA Type of Service (ToS) over TCPIIP to ensure preser-vation of SNA CoS traffic parameters and aid net-works in prioritizing SNA traffic

Programmers have created tables and software utili-ties to streamline the processing ofToS settings For example,iptables allows a table to be constructed with predetermined values that can be matched to the datagrams being processed Thus, only those with matching patterns are processed Masking utilities are available for accomplishing a similar task, but with more power and flexibility

In NIKHEF ping code, TOS bits can be set to enable the user to set priorities for the ping query Settings are between 0 and 255 See RFC 1455, RFC 1812

when special symbol sets are not available See mu.

U interfaceIn ISDN, 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 ofwirelines and

de-vices to create the all-digital circuit connection

nec-essary to send and receive digital voice and data

trans-missions

The U interface is a full-duplex link that works over

a single pair (2-wire) cable It interfaces a line

termi-nating switch in the telephone switching office with

a small interface device called a Network

Termina-tion device (NTI or NT2) at the customer premises

In the U.S., the NTI converts the 2-wire U interface

into a 4-wireSITinterface which, inturn,can

sup-port multiple devices in a single bus loop

configura-tion, such as a telephone, computer, or facsimile

ma-chine Alternately, in parts of Europe, the NT2

inter-faces with an S interface See ISDN interinter-faces for a

diagram

U reference pointA demarcation point in ISDN

ser-vices installedinNorth America, where the local loop

connects with the NT 1 device See U interface See

ISDN interfaces for a diagram

U Series RecommendationsA series of lTU-T

rec-ommended guidelines for telegraph switching These

guidelines are available for purchase from the lTU-T

Since lTU-T specifications and recommendations are

widely followed by vendors in the

telecommunica-tions industry, those wanting to maximize

interoper-ability with other systems need to be aware of the

information disseminated by the lTU-T A full list of

general categories is in Appendix C and specific

se-ries topics are listed under individual entse-ries in this

dictionary, e.g.,TSeries Recommendations See V

Series Recommendations

U-band Astronomical emanations ranging from

3200 to 3950Athat are usually detected with U

po-larimetric filters from the U, B, V+R, I

Johnson-Cousins broadband photometric system U-band

fre-quencies are emitted by some celestial bodies and

help us gain apicture ofour universe V-band energy

emanating from some galaxies has been detected and

U-band flares are occasionally recorded

U-band, optical In optical communications, an

band in the 1625 to l675-nm range Distributed-feeback and continuous-wave laser diodes are avail-able in U-band frequencies U-band systems are not

as common as C-bandIL-band, but it has been sug-gested that U-band signals may be multiplexed with S-band signals in dense wavelength division multi-plexed (DWDM) systems in much the same way ItV~T • (j·.Seti~I~~tJ.D1endafl4Jbs

u-cuser-central In ADSL, the standardized inter-face between the twisted-pair local loop to the sub-scriber premises and the plain old telephone service (POTS) splitter on the network (usually the central office) side of the link U-C2is a less-standard inter-face between the POTS splitter and the ATU-C (net-workADSL Transmission Unit) While functionally

Fiber Optics Illustrated Dictionary

Sampling of UL Standards Related to Telecommunications

UL No Descriptions of UL Numbers from Underwriters Laboratory

UL1409 Low-Voltage Video Products Without Cathode-Ray-Tube Displays: Antenna signal amplifiers,

CATV adapters and digital converters, channel balancers and processors, distribution amplifiers, commercial TV cameras, disc players, electronic viewfinders, internal distribution amplifiers, laser disc players, modulators, picture tube degaussers, power packs, power supply-battery chargers, satellite receivers and dish controllers, single-channel converters, teletext and television decoders, television descramblers, tuner adapters and power supplies, UHF amplifiers, tuners, and converters, VHF amplifiers and tuners, video printers, video-production -processing, -receiving, and -recording equipment, and video tape recorders

UL1418 Cathode-Ray Tubes: Bonded frame, laminated, prestressed picture tubes (CRT), rebuilt

picture tubes, picture tubes for business equipment, dental, and medical equipment

UL1410 Television Receivers and High- Voltage Video Products: Household and commercial

television receivers and monitors, and health care facility television equipment

UL1412 Fusing Resistors and Temperature-Limited Resistors for Radio- and Television-Type

Appliances: For use in appliances that do not involve potentials greater than 2500V peale

UL1414 Across-the-Line, Antenna-Coupling, and Line-by-Pass Capacitors for Radio- and

Television-TYpe Appliances: For nominal 125- and 250-V, 50- to 60-Hz circuits, includes double

protection capacitors rated 1.0 B5F maximum

UL1419 Professional Video and Audio Equipment: Video tape recorders, audio/video editing

equipment, audio/video receiving and processing equipment, signal transmission equipment, television cameras, video digitizers, video monitors, metering equipment, and similar equipment

UL1492 Audio-Video Products and Accessories: Audio and video products intended for use on supply

circuits Audio products and accessories intended for household use and involved with the reproduction or processing of audio signals Video products that are intended for household

or commercial use, that receive signals in ways such as off the air, through a CATVIMATV cable system, from a video-recorded medium, and from image-producing units Auxiliary products and accessories intended for use with audio or video products wherein the auxiliary and accessory products are separate and do not perform the desired function, but are used in addition to or as a supplement to products mentioned above Cellular telephones and similar transceiving devices used on a vehicle, boat, or the like, where the telephone interconnects to the telephone network through a radio transmitter and receiver Portable audio or video products of the types described above that are intended for use with a vehicular, marine, or any other battery circuit as the power supply means

UL6500 Audio/Video and Musical Instrument Apparatus for Household, Commercial, and Similar

General Use: This standard applies to the following apparatus that is to be connected to the

supply mains, either directly or indirectly, intended for domestic and commercial and similar general indoor use and not subject to dripping or splashing: radio receiving apparatus fQr sound or vision; amplifiers; independent load transducers and source transducers; motor-driven apparatus which comprise one or more of the above-mentioned apparatus or can be used only in combination with one or more of them, such as radio-gramophones and tape recorders; other apparatus obviously provided to be used in combination with the above-mentioned apparatus, such as antenna amplifiers, supply apparatus and cable-connected remote control devices; battery eliminators; electronic musical instruments; electronic accessories such as rhythm generators, self-contained tone generators, music tuners and the like for use with electronic or nonelectronic musical instruments; video apparatus intended for entertainment purposes in health-care facility locations; cellular telephones and similar transceiving devices used on a vehicle, boat, or similar location where the telephone

interconnects to the telephone network through a radio transmitter and receiver; portable audio or video apparatus intended for use with a vehicle, marine, or any other battery circuit

as the power supply means

UL1685 Vertical-Tray Fire-Propagation and Smoke-Release Test for Electrical and Optical-Fiber

Cables: Limits for each fire test to make the tests equally acceptable for the purpose of

quantifying the smoke The cable manufacturer is to specify, for testing each "-LS" (limited-smoke) cable construction, either the UL vertical-tray flame exposure or the FT4/IEEE 1202 type of flame exposure The same test need not be specified for all constructions Cont

face due to the asymmetry of the link See U-R.

U-DSL The U interface in a Digital Subscriber Loop

(D8L) system

V-law, Jl-law A pulse code modulation (PCM)

cod-ing and compandcod-ing data ITU-T standard used in

au-dio systems on computer multimedia peripheral

cards This takes some of the load of specialized

ap-plications off the central processing unit (CPU).Itis

often implemented in addition to A-law companding

and is suitable for compression of voice

communi-cations Note, this is technically J,l-law, but many

key-boards don't support the Mu (J,l) character and so it

is altematelywritten as Mu-Iaw or U-Iaw In fact, it's

even sometimes written M-Iaw since the Greek

sym-bol for uppercase J,l isM.See A-law, Mu-Iaw

U-planeIn ATM networking, as it applies to

Broad-band-ISDN reference model, the U-plane is the user

plane, a higher-level plane including all of the ATM

layers, which bears user application information.It

sits adjacent to the C-plane (control plane) and shares

physical and ATM layers with the C-plane The

M-plane (management M-plane) enables the transfer

ofin-working as it applies to Frame Relay bearer services, the U-plane parameters, such as throughput, maxi-mum frame size, etc., are negotiated through the C-plane Synchronization and coordination between the U-plane and C-plane are described in ITU-T Recom-mendation Q.923 See the Appendix for more detailed information on ATM

U-R user-remote In ADSL, the standardized inter-face between the twisted-pair local loop to the sub-scriber premises and the plain old telephone service (POTS) splitter on the premises.U-~is a less stan-dardized interface between the POTS splitter and the ATU-R (premises ADSL Transmission Unit) While functionally similar, the U-R interface is distin-guished from the U-C interface due to the asym-metry of the link See U-C

U.K Education&Research Networking Associa-tion UKERNA The trading name for the JNT Asso-ciation, which has managed the development and operation of the Joint Academic Network (JANET), since 1994, under agreement with the Joint Informa-tion Systems Committee (llSC) of the U.K Higher

Sampling of UL Standards Related to Telecommunications, cont

ULNo Descriptions of UL Numbers from Underwriters Laboratory

UL 1577 Optical Isolators: Optically isolated switches and insulation systems, photocouplers.

UL 1651 Optical Fiber Cable: Single and multiple optical-fiber cables for control, signaling, and

communications as described in Article 770 and other applicable parts of the National Electrical Code

UL 1690 Data-Processing Cable: Electrical cables consisting of one or more current-carrying

copper, aluminum, or copper-clad aluminum conductors with or without either or both (1) grounding conductor(s) and (2) one or more optical-fiber members, all under an

overall jacket These electrical and composite electrical/optical-fiber cables are intended for use under the raised floor of a computer room (optical and electrical functions

associated in the case of a hybrid cable) in accordance with Article 645 and other

applicable parts of the National Electrical Code

UL2024 Optical Fiber Cable Raceway: Covers the following types of optical fiber cable

raceways and fittings designed for use with optical fiber cables in accordance with

Article 770 of the National Electrical Code:

Plenum Evaluated for installation in ducts, plenums, or other spaces used for

environmental air in accordance with the National Electrical Code as well as general purpose applications;

Riser Evaluated for installation in risers in accordance with the National Electrical

Code as well as general purpose applications;

General Use Evaluated for general purpose applications only

UL 1459 Telephone Equipment: Cordless telephones, key systems private branch exchange

equipment, telephone answering devices, dialers, and telephone sets

UL 1863 Communication Circuit Accessories: Telecommunications equipment such as jack and

plug assemblies, quick connect assemblies, telephone wall plates, cross connect

enclosures, network interfaces, and connector boxes

UL 1950 Practical Application Guidelines On-Line Service (PAGOS): A reference service

providing information for understanding and applying the requirements ofUL Standards for Safety Of interest is the UL 1950 Standard for Safety of Information Technology Equipment, Including Electrical Business Equipment

Fiber Optics Illustrated Dictionary

and Further Education Funding Councils Thus,

UKERNA has responsibility for the education and

research communities' networking programs in the

U.K It further researches and develops advanced

electronic communications facilities See JANET

UA See User Agent

UAC User Agent client See User Agent

UART See universal asynchronous

receiver-trans-mitter

UASs unavailable seconds A measure of duration,

in seconds, during which a service or entity is not

available

UAT See user acceptance testing, user application

testing

UAWG See Universal ADSL Working Group

UBR See unspecified bit rate

UCA See Utility Communications Architecture

UCC See Uniform Commercial Code

UCF See UNIX Computing Forum

UCITA See Uniform Computer Information

Trans-actions Act

UCM 1 universal controller module 2 See

Univer-sal Call Model

Uda, Shintaro One ofthe designers of the Yagi-Uda

antenna, a sensitive, directional antenna which

worked in the higher frequency ranges and became

the model for thousands of antennas that came later

and are still in use See Yagi-Uda antenna

UDLC See Universal Digital Loop Carrier

UDP See User Datagram Protocol

UECT See Universal Encoding Conversion

Tech-nology

UFO 1 See UHF Follow-On 2 unidentified flying

object

UHF See ultra-high frequency

UHF On, Ultra-High Frequency

Follow-On UFO A U.S Naval, Air Force, and Command

communications satellite constellation intended to

supersede the aging FLTSAT and LEASAT satellite

systems The system is designed to provide interim

Global Broadcast Service (GBS), EHF, and Ka-band

transmissions UFO provides more modem

capabili-ties and more secure communications than the older

satellite communications systems Increased channel

capacity is available with Demand Assigned Multiple

Access (DAMA) technology UFO is intended to

pro-vide global coverage of four significant geographic

areas, including the U.S and three major oceans See

FLTSAT

UHTTP See Unidirectional Hypertext Transfer

Pro-tocol

m I Unix International A consortium of computer

software and hardware vendors promoting the

devel-opment and implementation of Unix, and of related

and other open software standards See Unix, UNIX

2 See user interface

uk.telecomAnonline USENET newsgroup

estab-lished in August 1991 to discuss topics related to

tele-communications in the U.K Topics include services,

prices, technical specifications, equipment

function-ing and options, ISDN, and the various telephone

carriers providing services

956

mffiRNA Seeu.K.Education&Research Network-ing Association

UL See Underwriters Laboratories Inc

U1ex, Georg Ludwig (1811-1883) A German chem-ist, Ulex is remembered for having discovered Ulex-ite, the "TV rock," a unique mineral that projects light through its structure by internal reflection Ulex found this rock in Chile in the mid-1800s The mineral was named in his honor by renowned geologist/mineralo-gist James Dwight Dana (1813-1895), a correspon-dent of Darwin See Ulexite

U1exite A fibrous substance of hydrated sodium cal-cium borate hydroxide It is named for its discoverer, Georg Ludwig Ulex Ulexite is a borate from the class

of carbonates The natural substance is found in the American southwest, South America and Kazakhstan

Itranges from translucent white to transparent and the chains ofsodium, water, and hydroxide are linked

in an interesting way

Like Iceland spar, Ulexite is a somewhat brittle, com-plex mineral with unique optical properties; when it has a veined structure, it can channel light through its fibers For example, if a I-in chunk of polished Ulexite is placed over an image, with the fibers per-pendicular to the image plane, the image is channeled through the mineral and projected virtually un-distorted upon the opposite (top) surface, much to the delight of the viewer This capability has caused it to

be dubbed the "TV rock."

Synthetic versions ofUlexite are fabricated in a va-riety ofmarbled colors to have aesthetic appeal while still retaining some of the optical qualities ofthe natu-ral substance Synthetic Ulexite may be coated on one side to maximize its light transmission properties See Iceland spar

ULP See upper layer protocol

Ultra Sniffer A kit-based, handheld radio commu-nications receiver designed to facilitate radio direc-tion finding, especially for "fox hunts," during which hobbyists get together totryto find a hidden trans-mitter This unit, from VK3TJNNKJXAJ, is a little larger than a deck ofcards.Itis attached to a 2-m cen-ter beam with three elements attached in the cencen-ter

at 90° from the center beam The unit is designed to overcome some of the limitations of other radio di-rection finders in terms of overcoming interference and selective tuning without increasing complexity (and knobs) See fox, sniffer

ultra-high frequency UHF A designation for a range within the radio frequency spectrum commonly used for broadcast communications, which ranges from

300 to 3000 MHz

ultra-high frequency(UHF)antenna Acategory of antennas which are designed to take advantage of the particular characteristics of ultra high frequency (UHF)waves Because ofthe wavelength differences between UHF and very high frequency (VHF) waves and the relationship of the rods on the antenna to the length of the wave, it is possible to make UHF an-tennas relatively small, with more branching elements comparedtoVHF antennas However, as UHF tele-vision broadcast signals are generally weaker than

and they must be designed and installed with greater

care to be effective See antenna, combination

anten-nas, VHF antennas

ultraviolet Electromagnetic radiation with shorter

wavelengths, between the violet part of the visible

spectrum and X-rays Although it cannot be seen by

humans, ultraviolet radiation is of commercial

sig-nificance because it can degrade many types of

ma-terials and pigments Commercially, it is used in a

variety of lamps, such as arc lamps, and can be used

to remove data from erasable/programmable

com-puter chips

In astronomy, ultraviolet sensing devices use

ultra-violet radiation focused through a spectrograph to

study the characteristics of celestial objects

Tele-scopes and some satellites are equipped with this

capability The Hubble Space Telescope and the

International Ultraviolet Explorer satellite enable

study of objects using ultraviolet light near the

vis-ible spectrum The Johns Hopkins Ultraviolet

Tele-scope extends the range to the far ultraviolet, that is,

the region further from the visible spectrum See

in-frared

umbrella antenna An antenna that resembles an

umbrella in that the lines extend out and down from

a central pole

UMLSee Unified Modeling Language

UMPIX The USOC code for telephony-related

main-tenance plan, tier 1, per line

VMSP See Unified Memory Space Protocol

VMTS See Universal Mobile Telecommunications

Systems

unattended call A situation that occurs when, for

example, an automatic dialing system dials a line,

then tries to pass the call to the first available human

agent, but no agent is available Consequently, the call

is abandoned This type of calling occurs in the

tele-marketing industry and the call is terminated in

or-der not to irritate a potential customer Unattended

calls are also used by collection agencies and the

sys-tem hangs up if no agent is available or if the call is

answered by an answering machine, thus not

imping-ing on the agent's time

unattended systems Devices or systems which

func-tion without a human operator or without significant

human attention except for installation and routine

maintenance and upgrades Unattended systems have

become prevalent since the late 1970s, when

com-puter automation became inexpensive enough to

in-corporate into a wide variety ofcomponents and

ma-chines Computer bulletin board systems were some

of the frrst information-rich systems to function 24

hours a day, and phone systems now are frequently

automated with menu selections and voice mail

op-tions Recently, faxback systems allow users to

re-quest product information or technical support in the

form of fax documents The system logs the phone

call, gets the customer's document selections from a

list ofoptions, then dials back the user's fax machine

and transmits the requested documents Unattended

systems generally function24hours per day at a

sig-businesses are willing to give up personalized service

in favor of the economy offered by automated sys-tems See Auto Attendant

unbalanced line A transmission line with two con-ductors (such as coax or a telephone circuit) with unequal voltages with respect to the ground In phone circuits, this is generally an undesirable condition unblanking The portion of the sweep in a cathode-ray tube (CRT) where the beam is turned on, with pulses from the generator See blanking

unbundled Products or services which are sold sepa-rately For example, a company may release a graph-ics card/monitor combination as a package deal, and later unbundle the items, that is, allow them to be sold separately in order to clear the products, get a higher return, or respond to market demand for one product over the other Contrast with bundled

Unbundled Network Elements UNE Telephone network services that are sold or leased through com-petitive local exchange carriers (CLECs) as un-bundled services from an incumbent local exchange carrier (!LEC) These physical and functional ser-vices, when broken down (unbundled) into discrete components, make it possible for them to be mixed and matched into a variety of new services that may

be optionally resold or leased to endusers by a vari-ety of providers UNEs came about as a result of the competition-supporting provisions of the Telecom-munications Act of 1996 UNEs include such aspects

as local loops, switches, information (databased) ser-vices, etc

The UNE model and Congressional decisions regard-ing UNE were controversial In 1997, AT&T re-sponded to a Circuit Court decision that defeated key provisions of the Federal Communications Commission's (FCC's) rules on UNEs AT&T's po-sition was that the rulings could open the door to com-petitive restructuring of existing services and mo-nopolization of new services by competing provid-ers, but at a higher cost, which would not result in the desired competitive benefits to users

Unbundled Network Elements - Platform In tele-phony parlance, UNE-Platform (UNE-P) services are combinations of Unbundled Network Elements (UNEs) that provide finished (end-to-end) services

to Competitive Local Exchange Carriers (CLECs) that are functionally equivalent to retail service of-ferings UNE-P products are intended only for resale

to endusers, not for the use of carriers themselves Examples of UNE-P services include plain old tele-phone service (POTS), public access line (PAL), ISDN Pri and Bri, digital switched service (D8S), and Centrex services

UNCSee Universal Naming Convention

underfill In semiconductor circuit assembly, mate-rial that seals components or fills holes or gaps, of-ten around solder joints where chips attach to circuit boards Underfill may insulate from possible electri-cal shorts or may provide structural support It may also help prevent abrasians and corrosion Underfill requires extra materials and time, and may need to

Fiber Optics Illustrated Dictionary

be cured, and thus is not always used, even when it

might improve fabrication quality

underfill, optical A situation in which the amount

or intensity oflight present does not fully fill an

ap-erture or grating structure or meet operational

mini-mums ofa component.Ifa point light source is much

narrower than an opening through which it is

shin-ing, the opening is said to be underfilled Similarly,

if a light source is smaller than theacceptance cone

of a light-carrying component, it is said to be

underfilled In grating structures, which have

differ-ent geometries depending upon the direction of the

incident light, the structure may be optimally filled

or overfilled in one plane and underfilled in others

In coupled optical fibers, particles or back reflection

may result in loss of light at the junction and

under-fill of the succeeding link in the light path

There is a relationship between the F number

(aper-ture diameter) and an illumination target (grating,

mirror, light pipe, etc.) such that a higher F number

may underfill the aperture Sometimes underfilling

is desired and may improve resolution At other times

it may result in incomplete or ineffective

function-ing of a system See acceptance cone, overshoot

Undersea News ServiceAninternational submarine

fiber optics news service that features selected press

releases from major newswire services, compiled and

published by KMI Corporation See KMI Corporation

undershoot See overshoot

Underwriters Laboratories, Inc UL UL is a

not-for-profit organization established in 1894.Itprovides

conformity, safety, and quality assessment services

and publications to a variety oforganizations,

includ-ing manufacturers In addition, UL provides

educa-tional materials, input to internaeduca-tional safety systems,

and assistance to various regional authorities

UL publishes a catalog of its standards and the

stan-dards themselves in print, on microfilm, CD-ROM, and diskettes The UL also sponsors a UL Standards Electronic BBS (accessed directly, or through the Web) The majority of the UL published standards have been approved as American National Standards

by the American National Standards Institute (ANSI)

UL has a number of publications of interest to pro-fessionals in the communications industry, including WireTalk for the wire and cable industry

http://www.ul.com/about/wtalk/index.htrnl

UL provides ISO 9000 standards quality registration through its accredited RvA, Registrar Accreditation Board(RAE)and other international quality affilia-tions It provides information on new international environmental management standards through ISO 14001

The full UL catalog is available on the Web, but the Sampling of UL Standards chart shows some tele-communications-related UL Standards which may be

of interest and which provide an idea of the types of use and safety issues concerned http://www.ul.com/ Underwriters Laboratory Inc assessment The UL provides a number ofconformity assessment services for product certification These include listing, clas-sification, field engineering, and various types of safety and performance testing The UL Conformity Assessment services chart shows some ofthe services relevant to telecommunications

Underwriters Laboratory Inc Mark UL Mark UL provides a number of listing marks to indicate that products or systems have been evaluated by UL and conform to certain specifications Those shown in the

UL Listing Marks chart are relevant to telecommu-nications

UNE See Unbundled Network Elements

UN!User Network Interface, User-to-Network Inter-face As specified by the ATM Forum, an ATM network

UL Conformity Assessment Services Related to Telecommunications

Service Brief Description

Listing Service A UL Listing Mark indicates that representative samples have been tested

and evaluated according to nationally recognized safety standards

Classification Service A UL Classification mark indicates that products have been evaluated for

certain properties under specified conditions

Component Recognition A service for factory-installed components in complete products

Certificate Service A service for completely installed systems

Field Engineering Service A service for installed products without UL Listing Marks or UL

Classification Marks

Testing Environ Products Evaluation of innovative environmentally friendly products

LAN Cable Performance Safety evaluations and evaluation of LAN cable according to industry

performance specifications, including TlAIEIA standards

Energy Efficiency Electrical appliances are certified according to U.S or Canadian standards

for energy efficiency through the UL Energy Verification

SDS Verification Testing Verification of input/output products to Honeywell's Smart Distributed

System (SDS) for compatibility of components to an industrial control communications network

958

public ATM network equipment, or connects between

Customer Premises Equipment (CPE) and public

net-work equipment See PMP, PCR, OeD, SCR

Unicamp A group at the State University of

Campinas, Brazil, formed in 1975 to deveop optical

fibers for TELEBRAS (Telecommunica~oes do

Brasil) The majority of optical fiber produced in

Brazil is based upon research in optical

communica-tions, nonlinear optics, and other phenomena

re-searched by Unicamp

unicastAtype oflntemet Protocol(IP)address

iden-tifier for a set ofinterfaces Unicast transmits a single

Protocol Data Unit (POD) to a single destination

(un-like multicast, where it may go to multiple

destina-tions) The fonnat of the ATM subinterface unicast

command is: atm smds-address <address> See

anycast, IPv6 addressing, multicast

UnicodeA character-encoding standard to support

text-encoding in data files Unicode, Inc was

origi-nallya collaboration between Apple and Xerox, who

produced the original specification They were later

joined by Adobe, Aldus, Borland, ffiM, Microsoft,

NeXT, Novell, Sun, and others Unicode has been

rolled in with an ISO specification as a subset ofISO

10646 Unicode is loosely based upon the widely

sup-ported Ascn standard, but in a greatly extended fonn

to include major world languages not represented

with Roman characters, including Cyrillic, Greek,

Arabic, Hebrew, Japanese Kana, Chinese bopomofo,

Korean hangul, and others Symbols, punctuation

marks, mathematical symbols, and technical symbols

are also supported Unicode uses a 16-bit character

set, supporting over 65,000 characters Each

charac-ter is assigned a unique 16-bit value No special

modes or control or escape sequences are needed

Unicode comprises the first 65,536 code points ofthe

use See Unicode Consortium

Unicode Consortium A nonprofit association founded in 1991 to promote and support the accep-tance and implementation of the Unicode character-encoding standard The Consortium publishes a pam-phlet on the Unicode specification The Unicode Technical Committee, descended from Unicode, Inc., now functions as part of the Consortium to actively maintain the standard See Unicode

unidirectionalMoving, responding, or transmitting

in one direction, or in only one direction at a time Unidirectional Hypertext Transfer Protocol UHTP A robust, unidirectional IP multicasting re-source transfer protocol suitable for one-way broad-casting over the Internet or over the television verti-cal blanking interval The protocol allows many view-ers to simultaneously access the broadcast site See broadcast data trigger

unified memory architectureAsystemo~which the video display drivers are integrated into the mother-board, and system random access memory(RAM)is used to buffer graphics displays, rather than having them as separate systems Some systems use this very effectively, providing graphics coprocessor chips, and allowing greater video graphics memory and more control over memory for programmers, applications, and users On other systems, this type of integration slows down the graphics rendering and overloads the CPU This is not the fault ofthe concept, but rather a result of how it is implemented

Unified Memory Space ProtocolUMSP Aconnec-tion-oriented network protocol corresponding to the session and presentation layers of the Open Systems Interconnect (OSI) model UMSP was submitted as

an Experimental RFC by A Bogdanov in December 2000

UL Listing Marks Related to Telecommunications Listing Mark Brief Description

UL Listing Mark Commonly seen, and indicates that samples of the product conform to UL

safety requirements according to UL published standards for safety

C-UL Listing Mark Canadian market products evaluated according to Canadian safety

requirements

Classification Mark Products evaluated for specific properties under specified conditions

These usually consist of industrial and building materials and equipment C-UL Classification Mark Classification Mark products intended for the Canadian market

Recognized Specific to components used in products sold as complete units, and thus Component Mark not usually seen from the outside There is also a Canadian version

International emc-Mark Products which conform to electromagnetic compatibility requirements of

Europe and/or U.S and/or Japan and/or Australia

Field Evaluated A product which is evaluated in the field rather than in a laboratory

Product Mark

Facility Registration A facility which has passed UL quality assurance standards,

Mark specifically ISO 9000-series and ISO 14001 (environmental)

Fiber Optics Illustrated Dictionary

UMSP uses transport layer service for reliable

deliv-ery (with acknowledgment data) UMSP creates a

network environment for organizing 128-bit address

space distributed among Internet nodes The

proto-col defmes connections management algorithms and

network primitive formats; it does not control local

node memory Connection parameters may be set in

a number of ways and systems with high protection

levels may be configured without restricting

appli-cation functionality See RFC 3018

unified messaging See integrated messaging

Unified Modeling Language UML A widely used

modeling language for specifying, constructing,

vi-sualizing, and documenting the artifacts of software

systems UML is intended to streamline and simplify

the process of software design It is a product of the

Object Management Group See Object Constraint

Library, Object Management Group

Unified User InterfaceDill.In the Envisat satellite

data communications services, theDillis a single

interface to User Service Facilities that enables

us-ers to access Envisat data services from any station

or access node using a standard Web browser The

UUI interprets the browser commands to the service

functions in the Envisat-l Payload Data Segment

(PDS)

Uniform Commercial Code UCc.Anadopted code

for conveying, clarifying, and permitting commercial

activities within the provisions ofthe UCC Act as they

apply to commerce within the 50 U.S states and some

of its territories The Act sets forth the terms and

con-ditions for commercial policies and activities

de-scribed within the Act, concepts applicable to law,

including actions, contracts, and remedies related to

commercial endeavors and disputes The UCC does

not strictly dictate the terms of contracts and

agree-ments between parties, but it helps to provide

guide-lines and default terms that provide a measure of

con-sistency and security for those conducting

commer-cial transactions The Permanent Editorial Board for

the Uniform Commercial Code provides oversight

and permission for the distribution ofUCC

informa-tion The Board publishes reports and drafts related

to UCc See Uniform Computer Information Trans-actions Act

Uniform Computer Information Transactions Act UCITA This was formerly an Article ofthe Uniform Commercial Code However, with the growth and prevalence of concerns specific to computing, it was felt that there was a need for a separate, related Act This became especially true when a large amount of electronic commerce begantoflow across the Inter-net UCITA is a uniform commercial code for soft-ware licensing and other computer information-re-lated transactions adopted by the National Conference

of Commissioners on Uniform State Laws in July

1999 See Uniform Commercial Code

http://www.ucitaonline.com/

uniform line A line which has essentially identical electrical characteristics throughout the transmission path

Uniform Resource Agent URA An architecture for

an agent system to provide Internet information ac-cess and management Encapsulation of protocol-specific actions enables the addressing of high-level Internet activities.Itis a structured mechanism for abstracting characteristics of desired information and distancing access processes from the client

The URA system was submitted as an experimental RFC by Daigle et al in October 1996 See RFC 2016 Uniform Resource Characteristic URC Adata for-mat for including meta-inforfor-mation, inforfor-mation out-side the resources in question, for the identification and location of these resources on the Internet See Uniform Resource Identifier When URCs were pro-posed, in the mid-1990s, it was suggested that they

be used in conjunction with Uniform Resource Names (URNs) instead ofURLS, to remove location dependencies

Uniform Resource Identifier URI Ameans to iden-tify resources on the Internet Because of the size and structure of the Internet, these resources may exist in one or more locations concurrently or may at times not be available at all

The syntax and encoding of the names and addresses

of objects has been gradually developed since 1990,

Common Uniform Resource Locator(URL)Schemes

ftp File Transfer Protocol Files and directories

http Hypertext Transfer Protocol Internet resources, Web pages

gopher Gopher Protocol File directories in Gopherspace

mailto Electronic mail address Internet electronic mail address

nntp USENET news using NNTP access Alternate means of accessing news

telnet Reference to interactive sessions Interactive telnet remote logon sessions

wais Wide Area Information Servers WAIS databases, searches, documents

file Host-specific file names Accessible files from various hosts

prospero Prospero Directory Service Resources on the Prospero service

name spaces A URI uses network protocols to

ex-press an address which maps onto an access

algo-rithm This is important because the Internet functions

with many different protocols for the transmission

and sharing of data In most cases, the data can be

converted to accommodate diverse formats

How-ever, some types of information are impractical to

convert, such as names and addresses of resources

By creating a type of object that can be labeled for

recognition and retrieval and a name space in which

these objects can reside, access and use ofthis

infor-mation can be facilitated A Uniform Resource

Lo-cator is an example of a URI

One of the more interesting developments on the

In-ternet has been the establishment of broadcasting

channels over which video and audio radio and

tele-vision programming can be viewed through Web

browsers and various other specialized software

pro-grams This has necessitated the definition and

orga-nization ofURIs appropriate for digital broadcasts

See Uniform Resource Characteristic, Uniform

Re-source Locator, Uniform ReRe-source Name, RFC 1630,

RFC 1736, RFC 1737, RFC 2396, RFC 2838

Uniform Resource LocatorURL Acompact string

representation for a resource available on the

Inter-net URLs have been in use since 1990 as Universal

Resource Identifiers in WWW A URL is a means to

locate resources, by providing an abstract

identifica-tion of its locaidentifica-tion Generally, a URL follows this

format:

<scheme>:<scheme-specific-part>

Examples:

http://www.abiogenesis.com/telecomdict

ftp://www.peanut.org/

Scheme names consist of a sequence of lowercase

characters from a to z, numerals0to9and the

char-acters"+"(Plus), "." (period), and "." (hyphen) It is

recommended that upper case be treated as lower case

in resolving a URL

A number of specific schemes for particular

proto-cols are standardized or commonly used and there is

a process for registering new ones Common schemes

(typed in lower case when used in a URL) are shown

in the Common Schemes chart See RFC 1630,

RFC 1738, RFC 1808, RFC 2396

Uniform Resource NameURN Similar in concept

to Uniform Resource Locators as a means to

iden-tify a resource or unit of information on the Internet,

but intended to manage an object space ofnames

ex-pected to have a longer shelf life URNs provide a

globally unique means of identifying information

about a resource or access to the resource itself

Func-tional specifications for URNs were proposed by

Sollins and Masinter and presented as a Request for

Comments in 1994 See Uniform Resource

Charac-teristics, Uniform Resource Identifier, RFC 1737

Uniform Resource Name Namespace for Object

IdentifiersURN Namespace for OIDs On the

In-ternet, an Object Identifier is a tree ofnodes,

syntac-example, the Internet OlD is 1.3.6.1 The OlD name-space specifies how an Object Identifier (ASN.l) is encoded as a Uniform Resource Identifier The ISO/

IEC Joint Technical Committee is the declared reg-istrant of the namespace

The scheme was originally submitted by M Mealling

as an Informational RFC, in November 2000, and up-dated in February 2001 See RFC 3061 which obso-letes RFC 3001

Uniform Resource Name Namespace for Public IdentifiersURN Namespace for PIDs Anamespace designed to enable Public Identifiers to be expressed

in Uniform Resource Identifier(URI)syntax Within XML, a public identifier is a simple string and, his-torically, public identifiers are not legal URIs in the context of the Web The URN namespace enables public identifiers to be encoded in URNs in a reli-able, comparable way through introduction of a for-mal public identifier namespace (publicid) The URN namespace scheme was submitted as an Informa-tional RFC by Walsh et a1 in August 2001 See RFC 3151

uniformityThe capability of a broadcast or other communications medium to deliver a steady and con-sistent signal within the desired range

uninterruptible power supplyUPS A safety and steady-service device which protects equipment and data by guaranteeing a sufficient and steady source

of electrical power in the event that other power sources are interrupted or lost

UPS systems may take their current from an alter-nating power supply while the system is up, store charges from this source, and then switch to an alter-nate source, such as a direct current storage battery

or separate alternate current generator in the event of power disruptions to the normal supply

UPSs are used on computers, phones, lighting sys-tems, and in emergency centers

:~~~rs;~eg~~,c~~~~fa~~;e[~ ~~~~~~~ ~:~~~~!.

queues, backup file systems, and applications which are reading or writing to storage media at the time of apower outage UPS systems can prevent loss offiles

in the process of being saved and prevent possible corruption to the medium on which they are being written

unipolarHaving only one pole, direction, or polar-ity

unique user identifierUUI.Anadministrative func-tion for uniquely recognizing or storing data on be-half ofan individual user This may be a name, num-ber, symbol, token, or biometric equivalent,

depend-ing upon the system A username is a type of UUI

commonly used to enable access to restricted com-puter systems UUIs are usedinassociation with thou-sands of different types of secured systems and ser-vices The New Zealand Customs Service, for ex-ample, uses a UUI system to register users and to administer their EDI clients using the Customs Computerized Entry Processing System

unit vectorIn mathematics/geometry, a vector