Fiber Optics Illustrated Dictionary - Part 82 ppsx

A data storage, retrieval, and protection system using multiple disk storage devices, a system commonly used in networks.. remote accessAnimportant aspect ofnetworking in which access to

Fiber Optics Illustrated Dictionary

only devices in computer networking, since most

devices employhandshakingto negotiate a

transmis-sion For example, a computer printer may seem to

be a receive-only device, but a printer has to be able

to tell the computer when it is ready to receive, when

it is busy printing and can't receive more data, and

when it is available again for other jobs or other

us-ers on a network This involves two-way

communi-cation It may even signal the sender about its

capa-bilities and configuration parameters Most

receive-only devices are passive devices or broadcasting

de-vices such as simple PA speakers, buzzers, lights, etc

receiver 1.A device for receiving signals, impulses,

or data transmissions 2 Adevice which captures, and

sometimes converts electromagnetic waves or signals

into a form meaningful to humans Receivers are

of-ten combined with tuners to specify the frequency

desired, and amplifiers to increase the power of the

signal See telephone receiver

Recognized Private Operating AgencyRPOA.An

ITU-T designation for telephone companies

provid-ing internetworkprovid-ing services

Recommended Standard 232 See RS-232 for an

entry and accompanying chart of Recommended

Standards

RECONreconnaissance

reconnaissanceApreliminary or exploratory survey

to gain information or data that can potentially be

analyzed to yield information (it's often difficult to

know in advance what data might later be useful or

significant) Reconnaissance and surveillance are

closely related activities Reconnaissance is

distin-guished from surveillance in that sUIVeillance is

keep-ing watch over or observkeep-ing someone, somethkeep-ing, or

some activities or phenomena Reconnaissance is

often used to support surveillance activities

Surveil-lance may also be used to obtain some ofthe data

col-lected in reconnaissance activities

Typing a few exploratory passwords into a computer

system is a reconnaissance activity intended to see if

it would be easy to breach a secure computer system

Using a computer to remotely view a scene captured

by a video camera is an example of a surveillance

activity that may also be part of a larger

reconnais-sance operation

Recording Industry Association ofAmerica RIAA

Anational trade organization representing the

record-ing industry The organization supports and promotes

the protection ofintellectual property rights and

busi-ness prosperity ofits members who collectively

pro-duce the vast majority of commercial sound

record-ings in the trade The RIAA became prominent in the

media when it opposed the alleged distribution of its

members' copyright materials by unauthorized users

through the Napster Web site

InOctober 2000, the RIAA announced that it was

going to develop a globally standardized system for

identifying digital sound files in order for the

copy-right owner of the files to be able to track their use

and to collect any royalties rightfully due for the

ma-terials This was intended to enable the distribution

ofdigital editions ofthe recordings quickly and easily

over the Internet without jeopardizing the economic viability of the people creating and vending the mu-sic http://www.riaa.com/

rectification 1 A condition in which current flow-ing through a material or circuit in one direction en-counters greater resistance than current flowing through in the opposite direction 2 The one-direc-tional processing of an alternating current (AC) rectifier 1 A material or circuit that offers greater resistance to an electrical current flowinginone di-rection than in its opposite didi-rection 2 A device for converting alternating current (AC) to direct current (DC) Rectifiers are commonly used on power trans-formers for electronics devices with power require-ments different from the power coming directly from

an electrical source Vacuum tubes were used as rec-tifiers in early radios, with selenium recrec-tifiers begin-ning to supersede them in the mid-1940s See coherer, crystal detector, piezoelectric

recursion 1.Returning, moving back upon 2 A re-petitive succession of elements or operations that af-fects the preceding elements or operationsin a like (although not necessarily identical) manner accord-ing to a finite rule or formula Recursive algorithms often generate data or images with the characteristic

of "selfsimilarity," with fractal display programs be-ing a popular, visually appealbe-ing example 3 See re-cursion

red alarmIn telephone transmissions systems, a criti-cal failure alert signal which occurs if an incoming signal is lost or corrupted This is implemented in various T3, Tl, or SONET network systems Red Book1 The original Compact Disc digital au-dio (CD-DA) specification, developed in the late 1970s and introduced in the early 1980s by Sony and Philips Audio sectors, tracks, and channels are speci-fled, along with other physical parameters The for-mat enabled up to 74 minutes of digital audio to be recorded at a sampling rate of 44.1 KHz, a rate that

is sufficiently good to support the recording of clas-sical music The Red Book was followed, in the mid-1980s, by the Yellow Book, which specified CD-ROM parameters See Yellow Book 2 In telephony, books in the lTU-T (formerly CCITT) 1984 series of recommendations 3 The Adobe PostScript Lan-guage Reference manual

Red BoxAnenvironment for running Windows ap-plications under Apple's Rhapsody on Intel-based computers and possibly on PowerPC-based comput-ers, generally analogous to the Blue Box environment for running legacy Mac operating systems under Rhapsody This would make it possible to have full compatibility with Intel-based operating systems such

as Microsoft Windows on Apple hardware See Blue Box, Yellow Box

red signalAnalert or failure signal or "stop" indica-tor used in many industries and in association with many different types of devices, networks, and gauges See yellow signal for a fuller explanation or red and yellow signals

red wireA color designation used bymMto indi-cate wires used to establish a hardware patch to

wire, yellow wire.

Reduced Instruction Set ComputingRISC Atype

ofprogramming and system architecture which uses

a set of simpler instructions performing single,

dis-crete functions to carry out an operation than would

be used in a comparable operation by a Complex

In-struction Set Computing (CISC) design Most of the

newer computers tend to incorporate RISC

architec-tures, although not all support circuitry enables the

full capabilities of RISC architecture to be used

Unlikeclsecommands, RISC commands are the

same size, which means that less time is required for

subsequent processing of the instructions, because

individual evaluation of the commands for size and

conversion to microcode is not required When RISC

software is compiled, it is evaluated to determine

which operations are not dependent on the operation

or results ofothers, and slates them for simultaneous

execution

Due to the reduced instruction set and processing that

takes place, the circuitry on RISC chips is simpler

than on mostelscchips, resulting in a smaller

physi-cal size and, usually, lower heat output

Not all chips are strictly RISC or CISC For example,

in the Intel line of processors, the Pentium chips are

a transitional architecture that maintains some

down-ward compatibility with the earlier CISC

architec-tures, while still incorporating some ofthe advantages

ofRiSC architectures The chips tend to be larger and

hotter than straight RISC chips, but meet a market

demand through a transition period

redundancyReplication, duplication, superfluity,

repetition Redundancy is important in computing

cess of transport, can have serious consequences to human safety, economics, or business transactions See redundant array of inexpensive disks

redundant array of independent netports RAIN ZNYX Network technology that provides a scalable, modular architecture for delivering high-perfor-mance, high-availability, customized intranet connec-tivity through clusters of network servers RAINswitch server switches were announced in 1997

to support RAIN implementation in Fast Ethemetworks

redundant array of inexpensive disksRAID A data storage, retrieval, and protection system using multiple disk storage devices, a system commonly used in networks RAID consists of multiple hard drive storage devices linked together to provide data mirroring or data striping and parity-checking across disks in order to record the information redundantly Duplication or data mirroring is primarily a function ofsoftware, whereas parity-checking requires a con-troller and is associated more closely with hardware Many RAID systems are SCSI-based

A basic low-end RAID center may consist of four drives, each with 2.1 Gbytes of storage, sometimes set up in a rack, talking through a centralized con-troller system, usually through a server

Although a certain amount ofstorage is inevitably lost due to duplication ofdata, the big advantage ofRAID systems is that they provide pretty good protection against data loss if a drive goes down There is less protection if several drives go down but, since this happens rarely and since companies are reluctant to back up data sufficiently often on systems like tape

Redundant Array of Inexpensive Disks (RAID) - Level Specifications in Brief

Level 0 Striping, no redundancy or error correction This can provide faster access, but does not

protect data from loss

Levell Disk mirroring Complete redundancy Provides data protection

Level 2 Byte striping, dedicates at least one drive for parity information Uses Thinking Machines,

Inc 's proprietary setup, which is not commonly used

Level 3 Generally used instead of level 2 Block striping will improve performance if data are

written in large blocks and simultaneous reads are used Distributed parity infonnation (originally required a dedicated parity disk, a stipulation removed in1994). In other words, when appropriately implemented, better performance and data protection can be achieved Level4 Similar to level 3, but larger data blocks are striped across disks; each drive is not

necessarily involved in each access

LevelS Block striping, parity information distributed across drives At least three drives are

required for a minimum implementation Each drive is not necessarily involved in each access Parity infonnation is also striped across disks Provides data protection and, in many cases, will improve performance This is a popular implementation ofRAID.

Level 6 Not consistently specified or implemented

Level 7 Similar to level4,with larger data blocks striped across disks Uses Storage Technology,

Inc 's proprietary caching mechanism and operating system

Fiber Optics Illustrated Dictionary

drives, the RAID alternative works well in~ractice.

Many RAID systems are "hot-swappable ' which

means that an individual drive can be pulled out and

replaced while the system is online, thus not

neces-sitating a system shutdown or inconveniencing

cur-rent users on the system

Specifications released in 1988 in the RAID paper

proposed five levels Since that time, changes and

enhancements have occurred; the levels are not

cut-and-dried since configuring various parameters, such

as stripe size, creates overlapping characteristics

be-tween the different levels Hybrid systems also

ex-ist Generally, however, to provide an introductory

understanding, the RAID levels can be summarized

as shown in the RAID Levels chart

In addition to redundancy and parity checking, a

RAID system may have some intelligent monitoring

incorporated into the system, which does periodic

checks and analysis and reports anomalies to the

con-troller The controller can then signal awarning which

allows the device administrator to check for

poten-tial problems, or swap out a drive before it fails See

dynamic sector repair, SMART

re-engineerTo step back from a system or process,

take a new look at it, and redesign it, sometimes from

the ground up, usually with the intention of making

it more efficient and cost effective Software often

has to be re-engineered, as legacy systems tend to be

slower and less efficient over time, due in part to the

way they are upgraded and, in part, because of

tech-nological improvements and changes in hardware

which are accommodated in a variety of ways

Mar-ket pressures also cause many software programs to

be released before their time, in which case, they may

be re-engineered before the next release Work

envi-ronments in companies that are growing or

down-sizing quickly often must be re-engineered as the

ways of organizing facilities and staff appropriate to

a small company are not necessarily appropriate to a

large company

reed relay switchA type of electronic telephone

switch developed in the 1960s Reed relay switches

began to supersede crossbar switches, which were

prevalent at the time, and some of the step-by-step

switches still in use Electronic switches opened up

possibilities for many new types of caller services,

such as Caller ID, Call Waiting, etc

reel-to-reel tapeMagnetic recording tape wound

onto separate round reels which are usually about

4-in to 8-in in diameter Although most tape is now

distributed on cassettes rather than reels, reel-to-reel

is still used in some professional recording studios,

especially ifeight or 16 tracks are required for sound

mixing and dubbing Gradually these reel-to-reel

sound recorders are being superseded by digital

re-cording media See cassette tape

Reeves, Alex H.ABritish engineer who is one ofthe

significant pioneers ofpulse code modulation (PCM)

or, as he calls it, "coded step modulation." PCM is a

fundamental quantization system used in audio

re-cording and transmission technologies Reeves

con-ceived the idea while working at the International

Telephone and Telegraph Corporation(lIT)in Paris

in 1937 and received several patents for the technol-ogy between 1937 and 1942 Reeves recognized the potential for PCM to counteract interference on trans-mitted speech communications In 1965, Reeves authoredThe Past, Present and Future ofPCM See

pulse code modulation

reference clockAclock considered very accurate or stable, which is used as a reference for other clocks

or processes, such as computer processes Quartz crystal clocks are considered very accurate due to their vibrational properties and are often used in com-puters and watches The speeds of various computer processes are describedinclock cycles Atomic clocks

are used to establish Coordinated Universal Time and

in satellite positioning systems which require accu-rate clock references

In multimedia editing environments, a reference clock is used to provide "house sync," that is, long-term synchronization of various audio or other sig-nals, which resolve to the reference clock rather than

to the time code signal See atomic clock, chase trigger, Coordinated Universal Time, quartz crystal, time code

reference vector equalizationRVE A derivative of transparent tone in band (TTIB) modulation and a basic aspect of linear modulation systems, RVE uti-lizes equalization for linear amplitude and phase cor-rection to improve transmissions It is suitable for trunked narrowband mobile radio systems, for ex-ample RVE enables a digital radio to equalize a trans-mission signal at the receiver increasing potential schemes for high bit-rate densities See linear modu-lation, tone in band

Referral WhoisSee RWhois

reflect1.To rebound from, to bounce off of, to im-pact and move away from as a result of the imim-pact

2 To provide a replicate image of, to mirror

reflector/director elementsOn antennas, two or more protruberances from the main rod that are usu-ally narrow and regularly spaced in an array Reflec-tor and direcReflec-tor rods help improve gain and directiv-ity of broadcast signals See Yagi-Uda antenna

reflectometerAdevice for measuring surface reflec-tance, that isradiantflux, the reflected radiant energy

per unit oftime This is useful for designing and test-ing reflective mirrors, parabolic reflectors, and other components that need to meet certain regulatory and operational standards The instrument may be pas-sive, measuring ambient reflectance, or active, sup-plying a light source (e.g., laser) and measuring the resulting reflection See interferometer

reflectometer, optical time domainOTDR A spe-cialized reflectometer for locating and assessing pos-sible sources of optical loss in longer fiber optic cables The instrument emits a light pulse and con-verts and analyzes the reflections from the pulse Depending upon the "echo" pattern, it may be pos-sible to more closely identify the source ofa problem

refractionThe change in the line of travel of an in-cident electromagnetic wave asitpasses from one form of matter (or lack of matter, as in a vacuum) to

energy encounters and interacts with the changed

environment having a different density and

compo-sition, the energy interacts with the surrounding

mol-ecules (or lack thereof) and its course is altered See

index of refraction for a full explanation See

bire-fringent; Ptolemaeus, Claudius

refractive indexSee index of refraction

refresh rate, scan rateThe rate per unit of time at

which information or an image is The rate is usually

dependent upon speeds that make it visible and

in-telligible to humans This phrase is frequently applied

to broadcast and computer display technologies,

es-pecially cathode-ray tube (CRT) displays in which the

action ofelectron beams on the phosphors is very

lim-ited and must be reinitiated (refreshed) in order for

the image to continue to be visible Refresh is a

gen-eral concept which applies to many different types

ofsituations in computing, from individual phosphor

refreshes to graphical user interface element

re-freshes

The refresh rates ofthe phosphors on the inside

coat-ing at the front of a cathode-ray tube will affect the

clarity and amount of flicker seen on the screen

Monochrome or gray scale monitors have longer

per-sistence; that is, the image from the excited phosphors

is visible longer, and thus do not need to be refreshed

as often as color images

Refresh of the entire CRT image is described as the

number of times per second the frame is redrawn

Refresh rates slower than about 20 to 40 frames per

second are perceived as flickering to the human eye,

especially if the image involves fast action Still or

slow-moving images do not need to be refreshed as

often

The refresh rate of a computer program image is a

combination of operating system and applications

programming, and is not simply dependent on the

hardware attributes of the system In order to

opti-mize speed on a computer display, the OS or

program-mer may choose to refresh only a section which has

just been manipulated or changed If the software

does not keep track of what is transpiring on the

screen or ifseveral processes are active at once, it may

seem that the display is slow to update or refresh a

new window, gadget, or element drawn in a paint

pro-gram

In general, quicker refreshes are desired over slower

ones, but the cost ofmore computing power and faster

hardware puts some economic constraints on the

re-fresh rates of various systems

refurbished equipmentUsed equipment that has

been serviced and tested by a technician to bring it

back to original operating condition If further work

is done and substantial numbers of parts replaced or

upgraded, it may also be referred to as

remanufac-tured equipment

Refurbished equipment, or refurbs, are usually

cleaned up and made to appear new or nearly new

Refurbished items are typically sold at a discount of

about 15 to 30% over the price of new ones

regenerate To restore, bring back to original

regeneration is an important issue Transmissions typically suffer from loss and interference over dis-tances, and any means that can be used to maintain a signal or regenerate parts or all ofa signal experienc-ing loss or change in some form is usually desired

There are many physical and digital schemes for re-generating systems In some digital systems, regen-eration may involve putting a signal back into its original form at the receiving end In a sense, single sideband transmissions are a type of regenerated transmission, since only a portion ofthe signal is sent

The opposite sideband and the carrier signal are math-ematically constructed, and the original signal thus reconstructed at the receiving end See regenerative repeater, relay, repeater, single sideband

regenerative repeaterA type of repeater used in communications that are characterized by uniformity

of length and signal to correct the timing of the sig-nal and retransmit the cleaned-up impulses These are common in older teletype communications See re-peater

Regional Bell Operating CompanyRBOC One of

a number of companies which were formed by the divestiture ofAT&T, which originated from the origi-nal Bell Telephone Company through a long, color-ful history of mergers and splits In the mid-1980s Judge Harold Greene broke AT&T into seven RBOCs For more detail, see divestiture, Consent De-cree of 1982, Modified Final Judgment

regional test bedRTB A regionally allocated loca-tion, lab, or systems setup that enables designers, de-velopers, or implementors to test their systems Test

Test beds are important in almost every industry, since testing can be a complex activity involving special-ized equipment and skills Most designers and devel-opers don't have the resources to set up individual test beds Test beds are often funded by universities, consortiums, and government grants, especially when they are designed to test products that have a big chance ofpromoting the common good or being com-mercially successful and widespread

registerA repository for data, a storage area which mayor may not also be used for data manipulation

There are many areas of telecommunications where registers are used Many computer chip architectures have registers for holding information about to be moved or manipulated Palette configurations for computer displays may be saved in color registers

Data modems have registers for setting various pa-rameters, with Hayes AT command"s"registers common Flags, configuration settings, etc are stored

in registers

Registration NumberAs part of the Federal Com-munication Commission's (FCC's) jurisdiction over equipment which may emit radiant waves that inter-fere with other equipment, appliances, radios, etc

There is a process ofsubmission, evaluation, and cer-tification which warrants that the equipment has

Fiber Optics Illustrated Dictionary

passed FCC requirements This Registration

Num-ber is not related to quality, suitability for a

particu-lar use, or other usability issues; it simply confirms

that the equipment falls within acceptable emission

standards

Reis, Johann Philip (1834-1874) AGerman

inven-tor who pioneered the transmission oftones and

pos-sibly also voice over wires Reis accomplished this

with various transmitters and other equipment that

he developed and publicly demonstrated in Frankfurt

to the Physical Society in 1861 No directly

verifi-able evidence indicates whether voice was

transmit-ted at the 1861 demonstration, but Reis' subsequent

work indicates that he recognized the potential for

voice communications and concentrated many ofhis

efforts in that direction, eventually developing a

tele-phone design that was not unlike teletele-phones actually

put into production in the United States some years

later

Subsequent inventors, excited about the

break-through, made improvements on Reis's early crude

mechanisms, while Reis himself continued to study

and improve the technology until his early death in

1874 See telephone history

relative intensity noise RIN The ratio of the mean

square optical intensity noise to the square of the

av-erage optical power, frequently described in decibels

(dB) A spectrum analyzer may be used to measure

RIN See Allan variance, Fourier transform

relayn. 1 To resend signals, objects, or

communi-cations to another node after which they are further

transmitted or transported 2.An electromagnetic

device in a circuit for providing automatic control,

which is activated by varying electrical impulses A

relay is usually combined with switches to control

when they open and close, and widely used to

auto-mate older telephone switching centers Thus, it was

important to design relays for durability, since they

had to open and close circuits many millions oftimes

Because the relay is essentially a simple mechanism,

it can be greatly varied by adjusting contact springs

and windings, thus producing a large variety oftypes

of relays Multicontact relays were developed in

or-der for numerous switching contacts to operate

simul-taneously See crossbar switch

Release to Pivot RTP A number portability

mecha-nism, similar to Query on Release (QoR), in which a

telephone number that has been ported from a release

switch returns the addressing information for

rout-ing a call (as opposed to the previous switch) If the

number has been transferred, the information may be

contained in the release switch or in an external

da-tabase See Query on Release

reliability An expression of the dependability of a

system under actual conditions ofuse See

availabil-ity, mean time between failures (MTBF)

Reliable Asynchronous Transfer Protocol RATP

A packet-based serial communications transfer

pro-tocol described by G Finn in 1984 RATP is intended

to facilitate reliable, easy-to-use communications

between computers through public telephone circuits

Based on the ubiquitous RS-232 standard, RATP

enabled full-duplex, point-to-point communication more simply than some of the other protocols at the time as well as some capabilities not found in others RATP is now considered a historic protocol See RFC 916

Reliable Data Protocol RDP Adata protocol for pro-viding reliable packet-based data transport services such as remote loading and debugging It is, in part, adapted from Transmission Control Protocol (TCP), and was submitted as an RFC by Velten et al in 1984 RDP supports the bulk transfer of data for various monitoring and control applications, as needed, with

a simpler set of functions than TCP Version 2 was submitted by Partridge and Hinden in 1990 to address some problems discovered in testing in 1986 and

1987 It makes changes to the protocol header and corrects some minor errors See RFC 793, RFC 908, RFC 1151

Reliable SAP Update Protocol RSVP Abandwidth-saving protocol developed by Cisco Systems for propagating services information RSUP enables rout-ers to reliably transmit standard Novell SAP packets only when a change in advertised services is detected

by the routers Network information can be trans-ported in conjunction with, or independently of, the Enhanced IGRP routing function for IPX

reluctance Opposition, or resistance in a magnetic circuit against the creation of magnetic flux Similar

to the concept ofresistance in an electrical circuit See resistance Contrast with permeability

REM 1 remote equipment module 2 See ring error monitor

remailer Any online electronic mail transit station which changes or prepends the header in such a way that the originating information is changed or ob-scured, or which intercepts mail and then forwards it

on to its destination Sometimes these remailers are LAN servers configured so that the header changes when incoming mail is served out to the local recipi-ents This is unfortunate in that the recipients cannot automatically reply to the sender and must manually type in the return email address in order to respond

to their correspondents This is not a recommended way of configuring a mail server and should only be done when a specific reason warrants it

Remailers are sometimes used irresponsibly Thou-sands ofget-rich-quick and commercial products pro-moters use remailers to obscure the origin of their online postings because there is much legitimate op-position to unsolicited commercial messages on pub-lic forums and in private email

Anonymous remailers are mail transit points which deliberately obscure the identity of the poster in or-der to ensure his or her privacy See anonymous remailer, spam

remapping On a computer system, remapping is moving data, often in the form of blocks, arrays, or tables, from one area of storage to another Memory remapping, address remapping, file location remapping, and keyboard remapping are some com-mon examples Remapping is sometimes used to

double-buffercomputer graphics screens - building

viewed by the user and then displaying it by

remapping the entire image to the video display area

Itcan improve the likelihood offast, clean transitions

See frame buffer

remote accessAnimportant aspect ofnetworking in

which access to computing services, devices, and

in-formation can be gained through a remote device on

the network, usually a computer tenninal or phone line

On a phone line, remote access to an answering

chine can enable a user to dial up the answering

ma-chine from a different phone, punch in some codes

to see if there are messages available, retrieve those

messages remotely, and even change the message on

the answering machine through the phone line

Remote access does not imply the level ofoperations

that can be accomplished, only that the device can be

accessed in some basic way Remote access terminals

vary greatly in their ability to interact with a server

or other user functions For example, on a basic

text-oriented "dumb terminal" connected to the main

com-puter with a serial line, the user may only be able to

execute simple text commands and won't be able to

display graphics or run sophisticated applications

locally

On the other end of the spectrum, some systems

pro-vide full access to remote applications, especially if

they are connected with a fast transmissions

proto-col over fiber In other words, there may be a

graphi-cal database program available on the server that the

user can run on a smart terminal as though the

termi-nal was the main computer Not all operating systems

can do this The X Window System is designed to

provide this type of capability in conjunction with

various Unix systems It has also been upgraded to

provide similar services over the Internet See X

Win-dow System 11

remote access concentratorRAC A network

sys-tem for interconnecting numerous multiple remote

telecommunications links to a local system such as a

local area network (LAN) Businesses with wide area

networks (WANs) and telecommunications

provid-ers make wide use of concentrators, as they aid in

channeling and aggregating many types ofequipment

in order to serve broader needs such as large

num-bers of employees or telecommunications clients

High-perfonnance concentrators may support several

services, including access, switching, and routing

Commercial RACs are created for many purposes

such as interconnecting multiple ISDN B-channel

lines to LANs through Ethernet or multiple computer

modems to TIIEI networks Multiple RACS can

sometimes be attached to one access switch

Depend-ing upon the protocols supported by a RAC, it may

be connected indirectly or directly to the public

switched telephone network (POTS)

Many vendors promote a similar product called a

re-mote access server (RAS), which is basically a

lower-end version of a remote access concentrator (usually

with fewer ports) Others refer to the operating

soft-ware for a RAC as remote access server softsoft-ware See

remote access server

cated to the provision and management of remote access transmissions.AnInternet Services Provider

is a type ofRACF that provides multiple subscribers with remote access to Internet services A telephone switching office is another type ofRACF, providing access to multiple remote telephones to its local sub-scribers

Within a particular business, a remote access facility can be established as a management or security sys-tem to control, authorize, log, and secure data and physical resources (printers, modems, etc.) used by

a variety of in-house or contract employees

mM provides the commercially trademarked Remote Access Control Facility system, first introduced for mainframes in 1976 The system is promoted to busi-nesses for the management and securing of valuable corporate data RACF supports OS/390 and z/OS software systems See remote access

remote access PBX Aprivate branch telephone ex-change which can be accessed from an outside line with appropriate authorization codes Once logged

on to the internal branch system, various features can

be used such as voice mail messages, long-distance calls connected and billed through the PBX, etc

remote access serverThe software and generally also the hardware on which the server software runs for managing transmissions between remote and lo-cal devices Remote access to the Internet and off-site printers, security monitors, and other network-able devices can be facilitated by a dedicated server, especially in situations where numerous people will access the service through limited resources (e.g., a limited number ofmodems) See remote access con-centrator

Remote Authentication Dial In User ServiceSee RADIUS

remote batch processingA means of submitting a computing job remotely to a processing system and receiving it back as or when the job is processed This

is rarely done at the consumer level, but it is still com-mon for high-end mathematical calculations, scien-tific research, and other intensive computing appli-cations which may require large amounts ofcomput-ing time or more sophisticated computofcomput-ing resources

In the earlier days of computing, remote batch pro-cessing, especially with punch cards, was the only type of service available, and it could take hours or days to receive the results of a simple calculation

Remote Call ForwardingA service in which a phone number is located in the central office of one exchange and any calls made to that number are for-warded (essentially by internally making a second call) to a line in another exchange This may be of value to businesses that want to maintain a local pres-ence without the expense of a local office, so that customers can call a local number instead of long-distance

remote concentration unitRCU.Anoff-site facil-ity or device in which multiple devices/services of the same basic type are aggregated and handled together within one basic management device

Fiber Optics Illustrated Dictionary

housing Telecommunications services (such as

In-ternet access or cable TV) and electrical power

dis-tribution are two examples ofRCD applications

remote controln A device to allow control of

an-other device without making direct physical contact

The control of the device may be through indirect

physical means (through a remote controller and

cable), a network (computer-controlled vending

ma-chines in another part of a building), or various

wire-less methods (infrared, FM, audible sound control,

etc.) Remote control of computers on a network can

be done through various telecommunications

prod-ucts, specialized remote applications and file

serv-ing software, or through operatserv-ing systems which

support this capability

remote control access RCA Access to restricted

ar-eas, rooms, or pieces of equipment through wired or

wireless remote devices Many environments and

types ofbuildings control access through remote

de-vices Examples include remote garage door

open-ers, key cards, parking barrier remotes, audio/video/

computer components with security feature remotes

and home automation remotes

remote diagnostics Systems diagnostics which can

be run from a remote location It is common for

higher-end routing and switching devices on a

com-puter network to be controlled through software at a

main administrative location This software typically

permits the running of test and diagnostic routines

and may show graphical diagrams ofproblems or

po-tential problems or bottlenecks On phone systems,

diagnostic checks can sometimes be carried out with

devices that generate specific tones or signals, which

can initiate processes at the other end ofa phone line

remote me access RFA A capability for accessing

electronic files from a system/terminal separate from

the file server RFA may be at some distance from

the file repository The Internet provides a

transmis-sion link to millions of file repositories around the

globe that can be accessed and downloaded by

vari-ous Web browsers and file transfer utilities See File

Transfer Protocol, ftp, Gopher

Remote Imaging Protocol RIP A protocol for

fa-cilitating the implementation of EGA-resolution

color images and mouse control from a remote

sys-tem RIP was developed to overcome the limitations

of text-based bulletin board system (BBS)

commu-nications (in the days before the World Wide Web)

Vector-based commands are sent and rendered

through a point-to-point network connection The

system has some limitations but is an interesting

so-lution to text-based remote terminal connections

through dialup links See Remote Imaging Protocol

script language

Remote Imaging Protocol script language

RIPscrip A scripting tool from TeleGrafix

Commu-nications, Inc for facilitating the development of

graphical user interfaces for computer bulletin board

systems (BBSs) supporting Remote Imaging

Proto-col (RIP) It is a 7-bit system to maintain

compatibil-ity with the many 7-bit communications systems

common through dialup connections (e.g., X.25)

RIPscrip works in conjunction with RlPaint and RlPterm for developing graphical interface screens and protocol needs See Remote Imaging Protocol remote job entry RJE Generically, this is the entry

of computer commands from a remote entry termi-nal, that is, a local termitermi-nal, for execution on a re-mote machine (e.g., a timeshared mainframe) This applies to individual job requests and to batch re-quests

The term has changed meaning somewhat as com-puters have become more common and less expen-sive Historically, remote job entry was a batch re-quest submitted on computer punch cards The cards were punched at a card-punching terminal by the pro-grammer, then physically handed together as a "job"

to a computer operator The operator queued the job with others that were pending and then inserted the card bundle into the computer's card reader for ex-ecution When the job was completed (or "crashed" due to errors), the operator would return the job cards

to the programmer along with any relevant results (or error messages) These days, jobs are usually submit-ted electronically through software requests rather than physically through punch card stacks See Re-mote Job Entry Protocol, reRe-mote programming Remote Job Entry Protocol RJEP RJEP was first submitted as an RFC by Chuck Holland in the early 1970s This generated quite a bit of interest and was corrected and developed further in RFC 407 in 1972 Remote job entry is a means by which a user can ex-ecute a computer processing job at a location (e.g., a mainframe) other than the local computer (e.g., a re-mote terminal) The user can thus submit ajob to an-other system acting as ajob server, which would pro-cess the job and deliver the results to the remote ter-minal through a TELNET connection File Transfer Protocol (FTP) served as the file transfer mechanism RJEP enables connections to be established indiv1du-ally or may leave the connection open for multiple submissions See File Transfer Protocol, remote job entry, RFC 360, RFC 407

Remote Mail Checking Protocol RMCP This low-overhead mail checking protocol was submitted as

an experimental RFC by Domer and Resnick in 1992

It provides a client/server-based mail checking ser-vice A program on the client's workstation uses RMCP to query a server to see if new email has been received for a specific user It is suitable for use with remote mail servers, such as those implementing Post Office Protocol (POP) The protocol is based on the User Datagram Protocol (OOP) port 50 Some au-thentication in the initial communication between client and server, at the cost of complexity See RFC 1339

Remote Operations Service Element ROSE.An

application layer service that provides the capability

to perform interactive remote operations through a request/reply mode ROSE is a generic information exchange technique which is not application-specific and not intended to define the operations it facilitates; this is left up to those implementing remote services

Itis defined as ISO 9072-1, and as an X Series

Syntax Notation One, X Series Recommendations.

remote procedure call RPC A means of making a

request to a remote system so that it appears to the

user as though the request is being fulfilled on the

local machine.Inother words, a user may open aword

processing program and load in a file The file may

actually reside on a computer in another room or

an-other city, but the user is unaware of any difference

in using the file from the remote system or using a

file from the local system as the RPC is transparent

to the user Another example would be the use of a

terminal communications program which accesses a

modem on another computer as though it were

physi-cally attached to the local machine Anumber

ofcon-ventions for making requests to a remote system, and

fulfilling those requests, have been developed The

RPC standard is a system for defining the parameters

of a remote communication

Remote Procedure Call Model RPC Model Based

on concepts of remote procedure calls (RPCs) in

which the caller and called procedure are typically

on physically separate systems exchanging data

through a communications link, the RPC Model

op-erates as a control mechanism functioning through the

caller's process and the server's process.AnRPC

in-terface provides a set ofremotely callable operations

provided by the server and provides a means to

man-age server resources made available to the remote

caller

As an example of one implementation, the caller

sends a call message with parameters to the server

process and holds for a reply When a reply message

is received, procedure results are extracted from the

data and the caller resumes execution of local

appli-cations (or makes further calls) While the model does

not exclude the possibility ofconcurrent processes on

the part ofthe client and server, it is sometimes

imple-mented with only one being active at a time

remote programming The capability whereby a

sys-tem can be programmed from a remote location,

ei-ther through a data network or phone lines, usually

after input ofappropriate authorization codes Remote

programming enables a field worker or telecommuter

to administer a system without being physically

present.Incomputing, remote programming is often

done by BBS operators who want to check and

man-age their systems when out of town By dialing their

own BBSs and logging in as the Sysop, they can

vali-date new users, check mail, configure the bulletin

board, and accomplish various maintenance tasks

throughaphone connection

Remote programming is often implemented in

high-end corporate and industrial software programs The

software is set up with security mechanisms so an

authorized programmer working for the software

ven-dor can dial into the customer's machine and do

rou-tine maintenance, software tune-ups, diagnostics, and

configuration without having to travel to the

customer's site, and during nonbusiness hours, if

needed This type of service is usually provided

through a separate service contract for a specified

remote site A facilities or equipment location which

is distant from the one presently occupied, or from which certain maintenance or administration tasks may be carried out Asales representative with a lap-top, a scientist withanintercom radio doing field re-search, and a computer terminal in an annex build-ing are remote sites often directly or indirectly com-municating with or through a main system at another location Remotes sites may be fixed or mobile

remote switching center RSC RSC has three gen-erally accepted meanings:(1)a secondary telecom-munications switch facility located at some distance from a main facility (at a remote location), (2) a switching center that is designed to serve remote sub-scribers who are often hundreds of miles away, (3) a switching center in a central or remote location that

is remotely managed and controlled through telecom-munications links from another center intended for that purpose

The first two meanings are traditional me"nings, es-tablished before sophisticated software and digital links were available, and are still relevant The third meaning is becoming more prevalent as telecommu-nications networks such as the Internet make it prac-tical to configure, manage, log, and maintain switch-ing services from a (remote) location offsite from the

actual switching facility Spelling the third as remote-switching centerhelps prevent ambiguity with tradi-tional meanings

Remote Telescope Markup Language RTML Just

as HTML is a markup language for representing in-formation and handling user requests on the Web, RTML is a markup language for handling user

re-:~~~~~~::~~~~~fs~ O::s~~~~~~s~~ special- ' RTML was initiated and has been adopted by the

Hands-On Universe (HOU) Project as a proposed standard for users to send requests to observatory re-motely controlled telescopes RTML 2.0 was released

by F Hessman in May 2001 This version had changes and additions to RTML 1.1 and subsequently was refined by Denny and Downey Denny then con-currently developed XRTML as an interim format;

this came to be called RTML 2.0 while Hessman's fuller implementation, called RTML 2.0b, was re-named RTML 3.0 Objects were removed from RTML 2.0 to create RTML 2.1, which is specifically

a request mechanism, with no support for the return

of data RTML 3.0, (released as 2.0b in July 2001) fully specifies a two-way communications protocol for submitting, updating, and acknowledging astro-nomical data requests, and for returning status infor-mation anddatarelated to these requests See Robotic Telescope Markup Language for the events leading

up to RTML

remote terminal A local computer terminal that en-ables remote access to services or accounts not avail-able on the local terminal Thus, a remote terminal

in a branch office could be used to communicate with

a centralized databank in the main office, for example Remote terminals may be wired or wireless,

Fiber Optics Illustrated Dictionary

or may be connected through a combination of

wire-line and wireless services (e.g., from the terminal to

a wireless access concentrator to a satellite link to the

main office)

Remote terminals are often classified asdumb or

smart terminals In general, dumb terminals are those

which have limited capabilities and may have few

applications that can be executed locally Dumb

ter-minals are used in situations where cost or security

are concerns Smart terminals are those that have

sig-nificant functionality on their own, even if not

con-nected remotely to another system

Remote User Telnet Service A means by which a

specific service of User Telnet may be accessed by

opening a port connection (107), a mechanism

sug-gested by M Mulligan and submitted as an RFC in

1982 by Jonathan Postel This enables remote access

to another system for logging in and executing

com-mands.Itis now considered a historic service See

RFC 764, RFC 818

remotely piloted vehicle RPY A land, water, air, or

space-based vehicle piloted from a remote location,

usually through radio control signals (though other

methods are theoretically possible) Military drones,

children's toys, and robots may be controlled this way

removable media Storage cartridges, drives, or

dis-kettes which can be swapped out and replaced with

another This provides a less expensive, portable

op-tion to numerous fixed storage devices In the

mid-1990s various cartridge drives became very popular,

as it was possible to store from 100 to 1000 Mbytes

on a cartridge not much bigger than a floppy The

problem was that every cartridge drive had a

differ-ent format and the formats were not intercompatible

More recently, super diskettes have been introduced,

which use normal floppy-sized disks that can store

100 MBytes, but the drives are still downwardly

com-patible with 1.44 floppies, so that it's not necessary

to have several devices attached to the computer It

is not clear, as of this writing, which of these

tech-nologies will prevail or whether another new one wi II

leapfrog them before one or the other is firmly

es-tablished

REN See Ringer Equivalence Number

REO removable erasable optical

repeat dialing This is both a function ofsome phones

and telephone/computer software programs, and a

service of some phone companies in which a

num-ber found to be busy can be repeatedly dialed until

the connection goes through, without the user

dial-ing the number again Repeat dialdial-ing is very

com-monly used in telecommunications software

pro-grams to dial up BBS numbers that are frequently

busy

repeater A device for receiving signals and

retrans-mitting those signals in order to propagate or amplify

the signal Repeaters are commonly used in

technolo-gies with signal attenuation and fade Repeaters are

used in digital and in analog systems and are often

spaced at intervals over paths that cover

long-dis-tances In digital systems, it is possible to reconstruct

the informational content of the signal; in analog

systems, more often the signal isamplified, which means that accumulated noise and degradation are still limiting factors Radio broadcast repeaters and microwave repeaters are examples ofcommon imple-mentations

In networks, a number of devices assist in the con-version and propagation of signals (bridges, routers, etc.) Arepeater is simpler than most ofthese devices, serving only to continue the signal and extend its range, or to clean it in its most basic sense, rather than

to change the informational content of the data See amplifier, bridge, doping, regenerative repeater

Repeatered Submarine Fiber Optic Cable Systems

RSFOCS A market study on underwater fiber optic cable systems published spring 1999 by IGIC as an update to a previous study

reperforatorAninstrument that translates received signals into a geometrically coded series of locations that are punched or otherwise impressed onto a pa-per tape Early telegraph systems and most of the early computing devices used reperforators These were then read with optical or tactile sensing devices

to turn the code back into human-readable form See chad

reperforator/transmitter RT A teletypewriter de-vice which includes both a reperforator for punch-ing received codes on paper tape, and a tape trans-mitting unit for sending the codes to a tape punching mechanism

repetitive pattern suppression RPS Ameans ofdata optimization which compresses digital communica-tions by removing repetitive patterns and reproduc-ing them at the receivreproduc-ing end

replication A process commonly used on computer systems for security, redundancy, distributed access,

or other backups In large companies and on the In-ternet, whole file archives are often replicated or mir-rored in order to provide access at a reasonable speed

to a larger number of uses Replication of data is a means to protect data in case of a serious problem with a system or storage device RAID systems are a means of replicating data to preserve data in case of

a fault Replication in the form of regular backups is recommended for all important computer data that need to be preserved In radio communications, trans-missions are sometimes repeated to improve the chances of a message getting through The replica-tion may be of individual small units of transmission

or may be repetition of a short message or signal See ALOHA

reprography Copying and replicating

REQ request

Request for Comments RFC A significantly influ-ential, formatted, open communications forum for technical experts which accepts, edits, numbers, pub-lishes, and disseminates Internet-related documents including protocols, draft and official standards, no-tices, opinions, and research Known as RFCs, these electronic documents form a body of more than 2200 contributions that provide a remarkable overview of the evolution of the Net, its structure, functioning, and philosophies

them are tiered and cannot be submitted without

pass-ing through previous categories in a specified order,

with specified waiting periods for comments and

re-visions from the RFC community

RFCs are not changed once they have been

submit-ted, assigned a number, and distributed Any changes

regarding an RFC must be submitted as a new RFC

There are many excellent RFC repositories on the

Internet, with good indexes and abstracts Anyone can

submit an RFC provided it is topical and follows the

official format and procedures This dictionary

in-cludes references to specific RFC numbers where the

author felt the technical origin of the information

would be of interest, and there is an overview of

sig-nificant RFCs in the Appendix For information on

submitting RFCs, see RFC 1543

Request for DiscussionRFD Similar to a Request

for Comments (RFC) in that it is a means on the

In-ternet to solicit and generate discussion on a

speci-fied topic However, it focuses on

intercommunica-tion on a topic in a slightly less formal or definitive

manner as opposed to specifying or defining a topic

once certain conclusions or draft/final working

mod-els have been developed, as in RFCs RFDs often

pre-cede RFCs but do not necessarily result in RFCs See

Request for Comments

Request for InformationRFI A solicitation and

notification of interest in receiving feedback or

in-formation on a specified topic, product, or process,

without implying that the requester necessarily wishes

to purchase or use that for which the information is

solicited See Request for Comments, Request for

Discussion

Request for ProposalRFP A call for proposals for

solving a problem or participating in a project

ARe-quest for Proposal process is used by many

institu-tions to initiate a project such as building a facility,

setting up a new organization, or developing a new

product or service People who submit RFPs usually

have a community or economic interest in shaping

or otherwise participating in the project A Request

for Proposal mayor may not be accompanied by a

Request for Quote See Request for Quote

Request for QuteRFQ A call for monetary

quota-tions for a particular project or venture The RFQ

pro-cess is commonly used by institutions to assess

various aspects of implementing a project and what

that project will cost Vendor input in the form of

Code

(no code)

I

H

E

PS

DS

S

Category Unclassified Informational Historical Experimental Proposed Standard Draft Standard Standard

may also give some idea of the timeline and type of materials involved It also serves as a fonn of pre-liminary contract (and is sometimes the only contract) once a vendor has been selected to undertake a job

An example of a simple RFQ would be a faxed page explaining that the cost of purchasing and installing

a new modem might be $200 An example of a more complex RFQ would be a 12-page document detail-ing the costs involved in settdetail-ing up a video security system in a business office or factory that can be monitored and controlled (through pan and tilt con-troIs) from a remote location through the Internet A Request for Quote may accompany a Request for Pro-posal or may sometimes be combined with a Request for Proposal See Request for Proposal

rerouteTo make a temporary or permanent change

in a data path Rerouting frequently occurs in large, dynamic networks like the Internet Systems where rerouting is common usually use a hop-by-hop method of routing in order to accommodate changes and to create new paths as needed In electronics, re-routing of a circuit may be accomplished by a patch

or shunt, a wire which bypasses the original path On Fiber Distributed Data Interface (FDDI) networks using dual rings, rerouting to the second, backup ring

is carried out ifa problem is detected on the primary ring

RES1 regional earth station 2 See Residential En-hanced Service

Resale and Shared Use decisionA decision of the Federal Communications Commission (FCC) to al-low competition in value-added networks

resamplingThe process of subsequent sampling of data, as image or sound data, and re-encoding it Re-sampling usually occurs when the original sample was not of the resolution level or compression rate desired Resampling may also occur in order to up-date or refresh information that may be changing, as

in Internet videocam shots, videoconferencing, etc See sampling

research and developmentR&D The study and associated development of theories, sciences, and technologies In communications, much R&D fo-cuses on creating marketable products R&D often consumes a huge proportion of a startup business's budget Many large corporations have R&D facili-ties to enable them to develop new products, includ-ing ffiM, Lucent Technologies (Bell), and Xerox

In many cases, R&D does not directly result in prod-ucts that can be manufactured and distributed, but the process of R&D indirectly contributes in surprising ways or, sometimes, decades later, when manufac-turing processes or needs change or catch up to the theories As an example, Charles Babbage's historic analytical engine (a pioneer computer concept) re-search and design was apparently theoretically sound, but the technology to build his machines did not ex-ist during his lifetime As a more recent example, space research has resulted in many portable and wireless communications technologies that might not have developed otherwise