Communication and network concepts.doc

8/14/2019 Communication and network concepts.doc

1/15

Chapter -16Computer Networking

1. NetworkA network is a collection of autonomous computers and devices connected to each other in order to allows computers to communicatewith each other and share resources(Printers, CD-ROMs, Modems etc. and information(!iles and pro"rams. ARPA#$% desi"ned for&' DOD was the first computer network.

A network in "eneral is composed of a wide variet of nodes that are connected ) transmission media. #etworks suppl their userswith communication channels. %he e*chan"e of messa"es is controlled ) communication protocols.

2. Need for Networking(Goals/Advantages

i !esour"e #haring. A network makes availa)le pro"rams or applications, data and peripherals availa)le to anone on thenetwork irrespective of the phsical location of the resources and the user, su)+ect to access permissions.ii Communi"ation and "olla$oration.A network allows users to share files, view other peoples work, and e*chan"e ideasmore efficientl. e can use e-mail and instant messa"in" tools to communicate uickl and to store messa"es for futurereference.iii !elia$ilit%.A network makes it easier to )ack up data on another computer( offsite server, a set of tapes, CDs, or other)ackup sstems which helps to recover data in case of an hardware or software failure.iv #e"urit%. 'ensitive files and pro"rams on a network are password protected and access is also restricted to authori/edusers. &hese "an also $e designated as '"op% inhi$it) in order to stop illegal "op%ing of programs.v Cost. Personal computers have )etter price0performance ratio than mini computers. 'everal PC1s can )e interconnected,with data stored on one shared file server machine. 2esides, networka)le versions of softwares are cheaper than individuallicensed copies of the software.vi !emote a""ess*A network allows "reater mo)ilit while maintainin" the same level of productivit. ith remote accessusers are a)le to access the same files, data, and messa"es even when there not in the office. %his access can even )e"iven to mo)ile handheld devices.

vii Centrali+ed software management.'hared pro"rams, on a network allows for easier installation and up"radin" of thepro"rams on one sin"le file server, instead of installin" and up"radin" individual workstations.viii ,orkgroup Computing.ork"roup software like Microsoft 2ackOffice ena)les man users to contri)ute to a documentconcurrentl. %his allows for interactive teamwork. Also workload on individuals can )e reduced ) distri)utin" work amon"different users on man workstations.

. isadvantages of Networksi 'erver faults stop applications )ein" availa)le to workstations.ii #etwork faults can cause loss of data or unavaila)ilit of resources.iii &ser work dependent upon network.iv 'stem open to hackers.v #etwork mana"ement can )ecome difficult.

. Appli"ations of Networksi !esour"e sharing. #etworks allow users to share3-

-Peripherals. $*pensive hardware can )e installed on a server computer and allow access to users in a controlled andcost effective manner. %his leads to efficient resource utili/ation.- !ile sharin". 'oftwares can )e installed centrall, instead of )uin" licenses for ever machine. Data can )e shared)etween applications and users.- 'hare stora"e. &sers can save their work on a central file server, which makes it easier to take )ackups also.

ii A""ess to remote data$ases. &sers can access remote data)ases over networks such as pu)lic li)raries, makereservations for airplanes, trains etc. 4t also promotes e-commerce.iii Communi"ation medium. $-mail, video conferencin", chattin" facilities makes it easier to transmit information andmessa"es around the "lo)e in a matter of seconds. #et meetin"s ena)le users to discuss issues without )ein" phsicallpresent at the same location.

0. volution of Networks%he precursor to the 4nternet, ARPA#$% was the first wide area packet switchin"network,created ) the &nited 'tates Defense

Advanced Research Pro+ect A"enc (DARPA in 5676 . ARPA#$% +oined computers of different tpes, runnin" various

operatin" sstems ) implementin" communication protocols common for all computers participatin" in the network.%he ARPA#et )e"an ) linkin" four locations3 'tanford &niversit, &C8A, &C 'anta 2ar)ara, and the &niversit of &tah.4n mid 9:1s, another federal a"enc, the #ational 'cience !oundation, created a new, hi"h-capacit network called #'!net,which was more capa)le than ARPA#$%.#'!net allowed onl academic research on its network. Another network called ;Commercial 4nternet $*chan"e (C4


2/15

or"ani/ations intranet tpicall includes 4nternet access )ut isfirewalledso that its computers cannot )e reached directl fromthe outside.

4tranetAn e*tranet is a private network that uses 4nternet technolo" and the pu)lic telecommunication sstem to securel share partof a )usinesss information or operations with suppliers, vendors, partners, customers, or other )usinesses. An e*tranet can )eviewed as part of a compans intranetthat is e*tended to users outside the compan. An e*tranet reuires securit andprivac. %hese can includefirewall server mana"ement, use ofdi"ital certificates or similar means of user authentication,encrptionof messa"es etc.

Companies can use an e*tranet to3

$*chan"e lar"e volumes of data usin" $lectronic Data 4nterchan"e ($D4

'hare product catalo"s e*clusivel with wholesalers or those >in the trade>

Colla)orate with other companies on +oint development efforts

?ointl develop and use trainin" pro"rams with other companies

Provide or access services provided ) one compan to a "roup of other companies, such as an online )ankin"

application mana"ed ) one compan on )ehalf of affiliated )anks

'hare news of common interest e*clusivel with partner companies

6. 5ow does nternet work

%he 4nternet is network of networks. A computer is not directl connected to the 4nternet. Rather it is connected to smallernetworks which in turn are connected throu"h "atewas to the 4nternet )ack)one.

7a"k$one Network A )ack)one is a lar"er transmission line that carries data "athered from smaller lines that interconnectwith it. e.". a )ack)one is a line or set of lines that 8A#s connect to for a A# connection or within a 8A# to span distancesefficientl.

nternet 7a"k$one. 2ack)ones tpicall consist of network routersand switchesconnected ) fi)er opticor $thernetca)les.%he trunk line has multiple fi)er optic ca)les com)ined to"ether to increase the capacit. (%he National #"ien"e 8oundation(#'! created the first hi"h-speed )ack)one in [email protected] normall do not connect to a )ack)one directl. 4nstead, the networks of #etwork 'ervice Providers or #'Ps orconnect to these )ack)ones and computers access the )ack)one indirectl.

9. Network &erminolog%

i Nodes(,orkstations. Anodeis an active electronic device that is attached to a network, and is capa)le of sendin",receivin", or forwardin" information over a communications channel. #odes can )e computers, personal di"ital assistants(PDAs, cell phones, or various other network appliances.

ii#erver.A network serveris a computer desi"ned to process reuests and facilitate the sharin" of data, software andhardware resources (e.". printers, modems etc. on the network. #etwork servers tpicall are confi"ured with additionalprocessin", memor and stora"e capacit to handle the load of servicin" clients. A network ma have multiple servers each ofwhich is identified ) a uniue name.'ervers can )e of two tpes3

Dedicated #on-Dedicated

edi"ated #erversBA dedicated serveris a computerin anetworkreserved for servin" the needs of the network. 4t1s onl +o)is to help workstations access shara)le data, software and hardware resources. 4t does-not dou)le up as a workstation.Dedicated servers ma )e cate"ori/ed as !ile servers, Printer servers, Modem servers etc. A network that uses a dedicatedserver is known as Master 'lave networks.

Non-edi"ated #erver- 4t refers to a workstation that can dou)le up as a server also. 'ince it performs the +o) of )oth a

workstation and a server it is slower and reuires more memor. %he networks usin" such a server are known as Peer-to-Peernetworks.

iii Network nterfa"e :nit(N:. ANC/N:is a device that is attached to )oth the workstation and the server and helps toesta)lish communication )etween the server and workstations. %he #4& is also called the %erminal Access Point(%AP or#etwork 4nterface Card(#4C. %he #4C manufacturer assi"ns a uniue phsical address to each #4C card known as the MAC

Address. A MAC address isa 7-)te address with each )te separated ) a colon e.". 5:323:=37=3$3!CMAC addresses map to lo"ical 4P addresses throu"h theAddress Resolution Protocol (ARP.

;. #wit"hing &e"hni


3/15

circuit switchin" where a specific phsical path to the num)er ou are callin" is reserved for the duration of our call.Durin" that time, no one else can use the phsical lines involved.%here are three phases in circuit switchin"3

o $sta)lish

o %ransfer

o Disconnect

=a"ket #wit"hing. Packet switchin" is a method of transmittin" messa"es throu"h a communication network, in

which lon" messa"es are su)divided into short packets of fi*ed )lock si/e.

2reakin" communication down into packets allows the same data path to )e shared amon" manusers in the network.

$ach packet carries the identification of the intended recipient, data used to assist in data correctionand the position of the packet in the seuence.

$ach packet is treated individuall ) the switchin" centre and ma )e sent to the destination ) atotall different route to all the others.

Packet switchin" is a form of store-and-forward switchin" sstem in which messa"es are stored inthe memor at the switch nodes and then transmitted to their destination and then deleted as soon as thereceipt at the ne*t node is acknowled"ed.

>essage #wit"hing. 4n this techniue no phsical path is esta)lished in advance in )etween sender and receiver.

4nstead, when the sender has a )lock of data (no limit on the si/e of a )lock to )e sent, it is stored in the first switchin"office (i.e. router then forwarded later at one hop at a time. 4t is a form of store-and-forward network. %he datapackets are stored on the disk till the are forwarded. Messa"e switchin" is thus an e*ample of a dela sstem or aueuin" sstem. Messa"e switchin" is still used for tele"raph traffic.
http://www.answers.com/topic/routerhttp://www.answers.com/topic/router


4/15

?. &ransmission >edia

%ransmission media or communication channel refers to the media used to connect two or more workstations in a network forthe purpose ofconvein" informationfrom asender(or transmitter to areceiver. %ransmission media can )e divided into twocate"ories3 "uided (ca)les and un"uided (waves throu"h air, water or vacuum. $*amples ca)les, microwave transmission,radio waves, infrared, telephone lines, satellites etc.

G: >A

Twisted pair cable.

Twisted-pair cableis a EFM(Eoice "rade medium ca)lin" that is used for telephone communications and most modern$thernet networks. 4t consists of a pair of identical wires wrapped to"ether in a dou)le heli*. %he pairs are twisted to provideprotection a"ainst crosstalk, the noise "enerated ) ad+acent pairs.

Crosstalk- %he )leedin" of a si"nal from one wire to another and which can corrupt si"nal and cause network errors. %his formof si"nal interference is called crosstalk.

Advanta"es Disadvanta"es

'imple structure Cannot carr si"nals over lon"distances without repeaters

!le*i)le 8ow )andwidthG unsuita)le for)road)and applications

$asil connected Ma*imum data rate of 5: m)ps

$as to install and maintain

8ow wei"ht and ine*pensive

,h% are "a$les twisted hen electrical current flows throu"h a wire, it creates a small, circular ma"netic field around thewire. hen two wires in an electrical circuit are placed close to"ether, their ma"netic fields are the e*act opposite of each other%hus, the two ma"netic fields cancel each other out. %he also cancel out an outside ma"netic fields. %wistin" the wires canenhance this cancellation effect. &sin" cancellation to"ether with twistin" the wires, ca)le desi"ners can effectivel provide self

shieldin" for wire pairs within the network media.

%wo )asic tpes of twisted-pair ca)le e*ist3 unshielded twisted pair (&%P and shielded twisted pair ('%P.

UTP Cable

&%P ca)le is used for variet of electronic communications. %he &%P ca)les can have ma*imum se"ment len"th of 5:: metersand is availa)le in followin" five cate"ories3

STP Cable

%pe &se

Cate"or 5 Eoice OnlG #o data (%elephone ire

Cate"or Data to H M)ps (8ocal%alk

Cate"or = Data to 5: M)ps ($thernet

Cate"or H Data to : M)ps (57 M)ps %oken Rin"

Cate"or Data to 5::: M)ps (!ast $thernet
http://en.wikipedia.org/wiki/Information_transferhttp://en.wikipedia.org/wiki/Information_transferhttp://en.wikipedia.org/wiki/Informationhttp://en.wikipedia.org/wiki/Senderhttp://en.wikipedia.org/wiki/Senderhttp://en.wikipedia.org/wiki/Receiver_(information_theory)http://en.wikipedia.org/wiki/Receiver_(information_theory)http://en.wikipedia.org/wiki/Receiver_(information_theory)http://en.wikipedia.org/wiki/Information_transferhttp://en.wikipedia.org/wiki/Informationhttp://en.wikipedia.org/wiki/Senderhttp://en.wikipedia.org/wiki/Receiver_(information_theory)


5/15

Shielded twisted-pair (STP)%his tpe of ca)le comes with shieldin" of the individual pairs of wires, which further protects it frome*ternal interference and crosstalk. Iowever it is more e*pensive and difficult to install and reuires proper "roundin" at )othends. 8ike &%P, this also has a ma*imum se"ment len"th of 5:: meters.

Coaxial Cable

Coa4ial "a$le, or "oa4, is a ca)le with a white insulator which surrounds the central copper wire and that this is surrounded )metal foil. A)ove this there is electrical shieldin" consistin" of laers of )raided wire, and, finall, a ru))eri/ed coatin". Coa*ialca)lin" is the primar tpe of ca)lin" used ) the ca)le television industr and is also widel used for computernetworks, suchas$thernet.Althou"h more e*pensive than standard telephone wire, it is much less suscepti)le to interference and can carrmuch more data. %he two tpes of coa*ial ca)les are i &hi"knet(ma4imum segment length- 0@@m ii&hinnet(ma4imum segment length-1;0m

Optical Fibre

An opti"al fi$er(or fi$re is a"lassorplasticfi)er that carriesli"htalon" its len"th. !i)re optic ca)les are increasin"lreplacin" copper conductors in A#sandMA#s)ecause of their uniue properties3

8ower si"nal loss per unit distance (resultin" in lon"er distances )etween repeaters

Ii"her Capacit (allowin" operation at hi"her data rates

'maller phsical si/e (allowin" more fi)res in a duct or trunk

4mmune to interference

Provides electrical isolation )etween local and remote nodes

Refer also to comparison ta)le for "uided media in )ook

Micro wave

hen a freuenc is hi"her than = FI/, it is named microwave. Microwave si"nals can )e transmitted alon" a strai"ht,uno)structed line from a transmitter to a receiver and can carr audio and video information. Microwave transmission consistsof a transmitter, receiver and the atmosphere. Distances of 5::Jm )etween towers are feasi)le. %he microwave transmissionis a line-of-si"ht transmission.

!eatures3

&se a hi"hl directional antenna to minimi/e interference.

!reuencies used for transfer of information are dedicated.

&suall supports point- to-point transmission.

Microwave si"nals can cross throu"h walls and phsical )arriers.

4n "eneral, it is relativel e*pensive )ut it ma )e the cheapest form of transmission over rou"h and

mountainous terrain.

Data rates up to :: M)ps are possi)le.

Microwave propa"ation is suscepti)le to weather effects like rains, thunder storms etc.

4t is an insecure communication

Radio Wave

%he transmission makin" use of radio freuencies is termed as radio-wave transmission. Radio freuencies are allocated todifferent operators normall in the ran"e of a)out 5: miles. $ach different radio si"nal uses a different sine wave freuenc.Radio waves are used for wireless transmission of sound messa"es, or information, for communication, as well as for maritimeand aircraft navi"ation. A radio setup has two parts3 %he transmitter and %he receiver. Radio wave can )e classified )freuenc and wavelen"th.

Satellite
http://www.webopedia.com/TERM/c/computer.htmlhttp://www.webopedia.com/TERM/c/computer.htmlhttp://www.webopedia.com/TERM/c/network.htmlhttp://www.webopedia.com/TERM/c/Ethernet.htmlhttp://www.webopedia.com/TERM/c/Ethernet.htmlhttp://www.webopedia.com/TERM/c/Ethernet.htmlhttp://www.webopedia.com/TERM/c/data.htmlhttp://www.webopedia.com/TERM/c/data.htmlhttp://en.wikipedia.org/wiki/Glasshttp://en.wikipedia.org/wiki/Glasshttp://en.wikipedia.org/wiki/Glasshttp://en.wikipedia.org/wiki/Plastichttp://en.wikipedia.org/wiki/Plastichttp://en.wikipedia.org/wiki/Lighthttp://en.wikipedia.org/wiki/Lighthttp://www.erg.abdn.ac.uk/users/gorry/course/intro-pages/wan.htmlhttp://www.erg.abdn.ac.uk/users/gorry/course/intro-pages/wan.htmlhttp://www.erg.abdn.ac.uk/users/gorry/course/intro-pages/man.htmlhttp://www.erg.abdn.ac.uk/users/gorry/course/intro-pages/man.htmlhttp://www.webopedia.com/TERM/c/computer.htmlhttp://www.webopedia.com/TERM/c/network.htmlhttp://www.webopedia.com/TERM/c/Ethernet.htmlhttp://www.webopedia.com/TERM/c/data.htmlhttp://en.wikipedia.org/wiki/Glasshttp://en.wikipedia.org/wiki/Plastichttp://en.wikipedia.org/wiki/Lighthttp://www.erg.abdn.ac.uk/users/gorry/course/intro-pages/wan.htmlhttp://www.erg.abdn.ac.uk/users/gorry/course/intro-pages/man.html


6/15

'atellite communication is special case of microwave rela sstem. 4t uses the snchronous satellite to rela the radio si"naltransmitted from the "round station. 4n satellite communication the earth station consists of a satellite dish that functions as anantenna and communication euipment to transmit and receive data from satellites passin" overhead. A num)er ofcommunication satellites, owned ) )oth "overnments and private or"ani/ations, have )een placed in stationar or)its a)out,=:: miles a)ove the earth1s surface. %hese satellites act as rela stations for communication si"nals. %he acceptdata0si"nals, amplif them, and retransmit them to another earth station. &sin" such a setup, data can )e transmitted to otherside of the earth in onl one step. Most communication satellites have multiple, independent reception and transmissiondevices known as transponders.

Infrared

nfraredtechnolo" allows computin" devices to communicate via short-ran"e wireless si"nals. ith infrared, computers can

transfer files and other di"ital data )idirectionall. %he infrared transmission technolo" used in computers is similar to that usedin consumer product remote control units such as %E remotes, automotive doors, wireless speakers etc. %he infrared li"httransmits data throu"h the air and can propa"ate throu"hout a room, )ut will not penetrate walls. %he infrared transmission has)ecome common in PDAs. 4t is a secure transmission.

Laser

8aser transmission reuires direct line-of-si"ht. 4t is unidirectional like mircrowave, )ut has much hi"her speed thanmicrowaves. %he laser transmission reuires the use of a laser transmitter and a photo-sensitive receiver at each end. %helaser transmission is point-to-point transmission, tpicall )etween )uildin"s.

1@. ata "ommuni"ation terms

ata Channel. A channel is the medium used to carr information or data from one point to another.

8re)road)and> usuall refers to hi"h-speed 4nternet access usin" this transmission techniue. 2oth D'8 and ca)lemodem are common )road)and 4nternet technolo"ies. %o ualif as a )road)and 4nternet service, the technolo" should as a"eneral "uideline supportnetwork )andwidthof at least 7 J)psin one direction.

7ase7and. A tpe of data transmission in which di"ital or analo" data is sent over a sin"leunmultiple*edchannel, such as an

$thernet 8A#. 2ase)and transmission use %DM(%ime Division Modulation to send simultaneous )its of data alon" the full)andwidth of the transmission channel. (4n other words it refers to analo" or di"ital data prior to an modification i.e. )efore theare mer"ed with other si"nals (multiple*ed or intermi*ed into a carrier wave (modulated.

7us. Device on a computers mother)oard that provides a data path )etween the CP&and attached devices (ke)oard,

mouse, disk drives, video cards, etc.. A computer )us receives a data si"nal from the CP& and drops it off at the appropriatedevice (for e*ample, the contents of a file in RAM are sent, via the )us, to a disk drive to )e stored permanentl. Conversel,data si"nals from devices are sent )ack to the CP&. On a network, a )us provides the data path )etween the variouscomputers and devices.

ata &ransfer !ate. D%R is the speed at which data can )e transmitted )etween devices. %his is sometimes referred to as

throu"hput. %he D%R of a device is often e*pressed in kilo)its or me"a)its per second, a))reviated as k)ps and m)psrespectivel. 4t mi"ht also )e e*pressed in Jilo)tes or Me"a)tes, or J20sec and M20sec.(Directl proportional to )andwidth

4tra e4planation - 7andwidth e4ample*4f ou think a)out a ca)le with si"nal )ein" sent across it as a hi"hwa and the data )its

in the si"nal as the cars. 4f two car len"ths is one wave len"th and )oth cars travel from point A to point 2 in one second, then thefreuenc would eual 5I/ )ecause one wave ccle was completed in one second. #ow, if we needed two )its of data (cars to )e
http://www.webopedia.com/TERM/b/digital.htmlhttp://www.webopedia.com/TERM/b/device.htmlhttp://www.webopedia.com/TERM/b/device.htmlhttp://www.webopedia.com/TERM/b/bps.htmlhttp://www.webopedia.com/TERM/b/byte.htmlhttp://www.webopedia.com/TERM/b/byte.htmlhttp://www.webopedia.com/TERM/b/analog.htmlhttp://www.webopedia.com/TERM/b/analog.htmlhttp://compnetworking.about.com/library/glossary/bldef-dsl.htmhttp://compnetworking.about.com/library/glossary/bldef-dsl.htmhttp://compnetworking.about.com/od/speedtests/g/bldef_bandwidth.htmhttp://compnetworking.about.com/od/speedtests/g/bldef_bandwidth.htmhttp://compnetworking.about.com/od/speedtests/g/bldef_bandwidth.htmhttp://compnetworking.about.com/library/glossary/bldef-kbps.htmhttp://compnetworking.about.com/library/glossary/bldef-kbps.htmhttp://www.webopedia.com/TERM/b/multiplexing.htmlhttp://www.webopedia.com/TERM/b/multiplexing.htmlhttp://www.webopedia.com/TERM/b/TDM.htmlhttp://www.webopedia.com/TERM/b/TDM.htmlhttp://www.answers.com/topic/cpuhttp://www.webopedia.com/TERM/b/digital.htmlhttp://www.webopedia.com/TERM/b/device.htmlhttp://www.webopedia.com/TERM/b/bps.htmlhttp://www.webopedia.com/TERM/b/byte.htmlhttp://www.webopedia.com/TERM/b/analog.htmlhttp://compnetworking.about.com/library/glossary/bldef-dsl.htmhttp://compnetworking.about.com/od/speedtests/g/bldef_bandwidth.htmhttp://compnetworking.about.com/library/glossary/bldef-kbps.htmhttp://www.webopedia.com/TERM/b/multiplexing.htmlhttp://www.webopedia.com/TERM/b/TDM.htmlhttp://www.answers.com/topic/cpu


7/15

transfered in one second from point A to point 2 across the ca)le (hi"hwa then the )andwidth would )e 5I/. 4f we needed to "et morecars across the hi"hwa in the same amount of time then the distance of the hi"hwa (ca)le or the distance )etween the cars (data )itswould have to decrease and the speed of the cars could sta the same.

7aud !ate vs 7itrateAs ou ma have alread "uessed ) )oth terms containin" the word rate, these are used to measure speeds inconnectivit. %he )aud rate is a measure of how man sm)ols are )ein" transmitted each si"nal. A sm)ol is an waveform chan"e orelectrical pulse that is used to transmitdata alon" the medium. On the other hand, the )itrate is a measure of the num)er of )its that are)ein" transmitted. Previousl, )aud and )itrates are used interchan"ea)l )ecause older modulation techniues onl allowed one )it to)e contained in each sm)ol. #ow, each sm)ol can contain more than )its resultin" in the )itrate )ein" much hi"her than the )aud rateith these cases, it is no lon"er accurate to interchan"ea)l use )itrate and )aud rate as the are no lon"er eual. %he "ross )itrate iseual to the )aud rate multiplied ) num)er of )its contained in each sm)ol. 'ince the )aud rate does not discriminate whethertheinformation it is transmittin" is data or +ust si"nalin" information used ) the hardware to snc, determine the path, and man otherthin"s. %he )aud rate includes overhead. 'o if each sm)ol contains H )its, the net )itrate is sli"htl less than four times of the )aud rate

%he difference is usuall ver small and should not affect the data transmission too much.

#ummar%* 5. %he )aud rate is a measure of the num)er of sm)ols )ein" transmitted each second while the )itrate is a measure of thenum)er of )its )ein" transmitted each second . $ach sm)ol that is )ein" measured ) the )aud rate can contain one or more )its =.%he )aud rate alwas includes the overhead in the measurement while the )itrate does not H. %he ma*imum )aud rate is eual to thepass)and )andwidth while the )itrate can )e much hi"her

11. &%pes of NetworkOne wa to cate"ori/e the different tpes of computer network desi"ns is ) their scope or scale.

AN(o"al Area Network A lo"al area network(AN is a computer networkcoverin" a small phsical area, like a

home, office, or small "roup of )uildin"s, such as a school, or an airport. %he followin" are the main characteristics of 8A#s

o smaller "eo"raphic ran"e

o tpicall owned, controlled, and mana"ed ) a sin"le person or or"ani/ation.

o hi"her data-transfer rates

o %he also tend to use certain connectivit technolo"ies, primaril$thernetand%oken Rin".

8A# confi"uration consists of B

o A file server 3 stores all of the software that controls the network, as well as the software and hardware which

can )e shared ) the computers attached to the network.o ,orkstation - computers attached to the file server (Mac or PCs. %hese are less powerful than the server.

o Network nterfa"e Cards

o Ca$les used to connect #4C in each computer.

>AN(>etropolitan Area Network >ANs, are lar"e computer networksthan 8A#s ran"in" from several )locks of

)uildin"s to entire cities . %he tpicall use wirelessinfrastructure orOptical fi)erconnections to link their sites. A MA#mi"ht )e owned and operated ) a sin"le or"ani/ation. %he will often provide means for internetworkin" of local networksMetropolitan area networks can span up to :km, devices used are modemand wire0ca)le e.". ca)le %E networks.

,AN(,ide Area NetworkA A# spans a lar"e "eo"raphic area, such as a state, province or countr. A#s often connect multiplesmaller networks, such as local area networks (8A#s or metro area networks (MA#s. %he worlds most popular A# is the 4nternet.Computers connected to a A# are often connected throu"h pu)lic networks, such as telephone sstem, or throu"h leased lines orsatellites.A network device called arouterconnects 8A#s to a A#. A#s tend to use technolo" likeA%M, !rame Relaand


8/15

a leased line

8A# is "enerall )roadcast schema A# is point-to-point.

7 Complete ownership ) a sin"leor"ani/ation

Owned ) multiple or"ani/ations or"overnment

@ !ew data transmission errors occur in8A#. 4t is )ecause in 8A# the distancecovered is ne"li"i)le.

Comparativel hi"her error rates.

9 $thernet and i-!i are the most currenttechnolo"ies used in a 8A#

!rame Rela,


9/15

More e*pensive than linear )us topolo"ies )ecause of the cost of the hu)s, etc.

c 7us topolog% -A linear )us topolo" consists of a main run of ca)le with a terminator at each end All nodes (file server,workstations, and peripherals are connected to the linear ca)le. A connector connects each computer or server to the )usca)le. %he source transmits a si"nal that travels in )oth directions and passes all machines unless it finds the sstem with4P address, the intended recipient. %he data is i"nored in case the address is unmatched.

Advantages of a inear 7us &opolog%

$as to connect a computer or peripheral to a linear )us.($as to e*tend

Reuires less ca)le len"th than a star topolo".

isadvantages of a inear 7us &opolog%

$ntire network shuts down if there is a )reak in the main ca)le.

%erminators are reuired at )oth ends of the )ack)one ca)le.

Difficult to identif the pro)lem if the entire network shuts down.

#ot meant to )e used as a stand-alone solution in a lar"e )uildin".

!ault identification is difficult as network is not centrali/ed in an particular node.

d !ing topolog% -A network topolo" that is set up in a circular fashion in which data travels around the rin" in one directionand each device on the ri"ht acts as a repeater to stren"then the si"nal as it moves ahead. !DD4, 'O#$% or %oken Rin"technolo"ies are used to )uild rin" technolo". A token, or small data packet, is continuousl passed around the networkwhich is reserved when a device needs to transmit ) attachin" the data packet to it.

Advantages of a !ing &opolog% 'hort ca)le len"th

#o wirin" closet space reuired

'uita)le for optical fi)res

isadvantages of a !ing &opolog%

#ode failure causes network failure.

Difficult to dia"nose faults.

#etwork e*pansion and reconfi"uration is difficult.

e &ree topolog% 3A tree topolo" com)ines characteristics of linear )us and star topolo"ies. 4t consists of "roups of star-confi"ured workstations connected to a linear )us )ack)one ca)le. %ree topolo"ies allow for the e*pansion of an e*istin"

network, and ena)le or"ani/ations to confi"ure a network to meet their needs.

Advantages of a &ree &opolog%

Point-to-point wirin" for individual se"ments.

'upported ) several hardware and software venders.

isadvantages of a &ree &opolog%

Overall len"th of each se"ment is limited ) the tpe of ca)lin" used.

4f the )ack)one line )reaks, the entire se"ment "oes down.

More difficult to confi"ure and wire than other topolo"ies.

0-- !ule -A consideration in settin" up a tree topolo" usin" $thernet protocol is the -H-= rule. One aspect of the

$thernet protocol reuires that a si"nal sent out on the network ca)le reach ever part of the network within a specifiedlen"th of time. $ach concentrator or repeater that a si"nal "oes throu"h adds a small amount of time. %his leads to the rulethat )etween an two nodes on the network there can onl )e a ma*imum of se"ments, connected throu"h Hrepeaters0concentrators. 4n addition, onl = of the se"ments ma )e populated (trunk se"ments if the are made of coa*iaca)le. A populated se"ment is one that has one or more nodes attached to it . 4n !i"ure H, the -H-= rule is adhered to. %hefurthest two nodes on the network have H se"ments and = repeaters0concentrators )etween them.

f) >esh &opolog%- Mesh topolo"iesinvolve the concept of routes. $ach node on a mesh is connected to more than onenode so that a messa"es sent on a mesh network can take an of several possi)le paths from source to destination. Amesh network in which ever device connects to ever other is called a full mesh. %his is "enerall used in lon" distancenetworkin".

7enefits

e*tensive )ackup, reroutin" and pass throu"h capa)ilities.
http://www.edrawsoft.com/Mesh-Network.phphttp://www.edrawsoft.com/Mesh-Network.phphttp://www.edrawsoft.com/Mesh-Network.php


10/15

ena)les communication even when there is a intermediate node failure usin" an alternative route.

1. Network evi"es4nternetworkin" devices are products used to connect networks. As computer networks "row in si/e and comple*it, so do theinternetworkin" devices used to connect them. %he main purpose of havin" these devices is3

%o allow a "reater num)er of nodes to )e connected to the network.

%o e*tend the distance over which a network can e*tend.

%o locali/e traffic on the network.

%o can mer"e e*istin" networks.

%o isolate network pro)lems so that the can )e dia"nosed more easil.

>odem.('hort for modulator-demodulator.) 4t is a computer peripheral that allows ou to connect and communicate with othercomputer via telephone line. Modem chan"es the di"ital data from our computer into analo" data(modulation, a format thatcan )e carried over telephone lines and reconverts the analo" si"nal )ack into di"ital datademodulation that the recipientcomputer can understand. %he standardinterfacefor connectin"e*ternal modemsto computers is called RS-232.%here arealso modems that come as an e*pansion )oardthat ou can insert into a vacant e*pansion slot.%hese are sometimes calledonboardorinternal modems.

!D-0. %he Re"istered ?ack-H connector is commonl used for network ca)lin" and for telephon applications. 4t is an ei"htwire connector which is commonl used to connect computers on the local area networks, especiall $thernets. 4t is similar to

telephone connector R?-55 e*cept that it has ei"ht wires as compared to H in R?-55.

5&!N& CA!.%pe of 8A# card developed ) smartest> device of them all. A router records the address information of everthin" connected to it like a switch2ut it also records the address of the ne*t closest router in the network. (ou can pro"ram this as the >default "atewa.> Arouter reads even more of the information in the address of a packet and makes an intelli"ent decision a)out what to do with

the data )ased on the address. !or e*ample, if a router receives an out)ound packet that has a destination address that is notin its ta)le, it forwards the packet to the default "atewa, rather than ever device attached like a switch does. %his is how data
http://www.webopedia.com/TERM/S/standard.htmlhttp://www.webopedia.com/TERM/I/interface.htmlhttp://www.webopedia.com/TERM/I/interface.htmlhttp://www.webopedia.com/TERM/E/external_modem.htmlhttp://www.webopedia.com/TERM/E/external_modem.htmlhttp://www.webopedia.com/TERM/E/external_modem.htmlhttp://www.webopedia.com/TERM/E/expansion_board.htmlhttp://www.webopedia.com/TERM/E/expansion_slot.htmlhttp://www.webopedia.com/TERM/E/expansion_slot.htmlhttp://www.webopedia.com/TERM/I/internal_modem.htmlhttp://www.webopedia.com/TERM/I/internal_modem.htmlhttp://searchnetworking.techtarget.com/definition/local-area-network-LANhttp://searchnetworking.techtarget.com/definition/local-area-network-LANhttp://searchnetworking.techtarget.com/definition/protocolhttp://searchnetworking.techtarget.com/definition/Ethernethttp://searchnetworking.techtarget.com/definition/Ethernethttp://searchnetworking.techtarget.com/definition/Token-Ringhttp://www.webopedia.com/TERM/R/router.htmlhttp://www.webopedia.com/TERM/R/router.htmlhttp://www.webopedia.com/TERM/R/device.htmhttp://www.webopedia.com/TERM/R/device.htmhttp://www.webopedia.com/TERM/R/packet.htmhttp://www.webopedia.com/TERM/N/network.htmlhttp://www.webopedia.com/TERM/R/local_area_network_LAN.htmhttp://www.webopedia.com/TERM/R/local_area_network_LAN.htmhttp://www.webopedia.com/TERM/R/local_area_network_LAN.htmhttp://www.webopedia.com/TERM/W/WAN.htmlhttp://www.webopedia.com/TERM/W/WAN.htmlhttp://www.webopedia.com/TERM/I/ISP.htmlhttp://www.webopedia.com/TERM/I/ISP.htmlhttp://www.webopedia.com/TERM/I/ISP.htmlhttp://www.webopedia.com/TERM/G/gateway.htmlhttp://www.webopedia.com/TERM/G/gateway.htmlhttp://www.webopedia.com/TERM/G/gateway.htmlhttp://www.webopedia.com/TERM/S/standard.htmlhttp://www.webopedia.com/TERM/I/interface.htmlhttp://www.webopedia.com/TERM/E/external_modem.htmlhttp://www.webopedia.com/TERM/E/expansion_board.htmlhttp://www.webopedia.com/TERM/E/expansion_slot.htmlhttp://www.webopedia.com/TERM/I/internal_modem.htmlhttp://searchnetworking.techtarget.com/definition/local-area-network-LANhttp://searchnetworking.techtarget.com/definition/protocolhttp://searchnetworking.techtarget.com/definition/Ethernethttp://searchnetworking.techtarget.com/definition/Token-Ringhttp://www.webopedia.com/TERM/R/router.htmlhttp://www.webopedia.com/TERM/R/device.htmhttp://www.webopedia.com/TERM/R/packet.htmhttp://www.webopedia.com/TERM/N/network.htmlhttp://www.webopedia.com/TERM/R/local_area_network_LAN.htmhttp://www.webopedia.com/TERM/W/WAN.htmlhttp://www.webopedia.com/TERM/I/ISP.htmlhttp://www.webopedia.com/TERM/G/gateway.html


11/15

moves onto, and throu"h, the 4nternet. Routers are also capa)le of lookin" at the source address of a data packet and makin"decisions )ased on that as well. %his means the can tell the difference )etween traffic that ori"inates on our network andtraffic that comes from outside. 'witches and hu)s cant do that (at least in a home users price ran"e. %his means that if arouter receives an in)ound packet that is addressed to somethin" not attached to it, it simpl drops it and our local networkdoesnt have to deal with it. A switch would forward it to all our networked devices and force them to decide whether or not isshould )e read. %his can clo" up our local network with useless traffic.

Gatewa%. A "atewa is a networkpoint that acts as an entrance to another network. %he main +o) of a "atewa is to connectdissimilar networks. 4t esta)lishes an intelli"ent connection )etween a local network and e*ternal network with completeldifferent structures. 4t is capa)le of performin" )oth data translation and protocol conversion (e.". $thernet 8A# to '#A('stems #etwork Architecture. 4n homes, the "atewa is the4'Pthat connects the user to the internet. 4n enterprises, the"atewa node often acts as a pro* serverand afirewall.A "atewa can )e implemented in hardware, software or )oth, )utthe are usuall implemented ) software installed within a router.

1. Network esign

&he ;@-2@ rule. 9:0: means #o more than : percent of the network traffic should )e a)le to move across a )ack)one and9: percent of the traffic on a network se"ment should )e local. %his is to ensure that there is less network traffic con"estion andproper use of )andwidth.

AN 5ardware- ,hen to use 5u$s/7ridges/#wit"hes/!outers.!epeaters- distance )etween computers0Iu)s more than 5:: m appro*.5u$B used to connect more than computers with each other. (Pro)lems B share )andwidth, cannot filter network traffic.7ridgeB used to se"ment two 8A#'. Can filter network traffic )ased on MAC address.#wit"hB Provides each se"ment with dedicated )andwidth.!outer- !ilters network traffic )ased on 4P addresses.
http://searchnetworking.techtarget.com/sDefinition/0,,sid7_gci212644,00.htmlhttp://www.webopedia.com/TERM/I/ISP.htmlhttp://www.webopedia.com/TERM/I/ISP.htmlhttp://www.webopedia.com/TERM/P/proxy_server.htmlhttp://www.webopedia.com/TERM/F/firewall.htmlhttp://www.webopedia.com/TERM/F/firewall.htmlhttp://www.webopedia.com/TERM/F/firewall.htmlhttp://searchnetworking.techtarget.com/sDefinition/0,,sid7_gci212644,00.htmlhttp://www.webopedia.com/TERM/I/ISP.htmlhttp://www.webopedia.com/TERM/P/proxy_server.htmlhttp://www.webopedia.com/TERM/F/firewall.html


12/15

10. Communi"ation =roto"ols

=roto"ol. A network proto"oldefines rules and conventions for communication )etween network devices. Protocols forcomputer networkin" all "enerall usepacket switchin"techniues to send and receive messa"es in the form ofpackets.#etwork protocols perform the followin" functions3

Provide mechanism for devices to identif and make connections with each other(wired 0wireless.

'pecif formattin" rules for how data is packa"ed into messa"es, sent and received.

'upport messa"e acknowled"ement and data compression.

%he tpe of error checkin" to )e used.

nternet =roto"ols%he 4nternet Protocol famil contains a set of related (and amon" the most widel used network protocols. 2esides4nternetProtocol (4Pitself, hi"her-level protocols like %CP, &DP, I%%P,and !%Pall inte"rate with 4P to provide additional capa)ilities.'imilarl, lower-level 4nternet Protocols likeARPand 4CMPalso co-e*ist with 4P. %hese hi"her level protocols interact moreclosel with applications like e) )rowsers while lower-level protocols interact with network adapters and other computerhardware.!outing =roto"olsRoutin" protocols are special-purpose protocols desi"ned specificall for use ) network routerson the 4nternet. Commonroutin" protocols include $4FRP, O'P! and 2FP.

#ome "ommon =roto"olsa. 5&&= 'hort for Iperte*t %ransfer Protocol, the underlin" protocolused ) theorld ide e). 4t defines how messa"es

are formatted and transmitted, and what actions e) serversand)rowsersshould take in response to various commands.I%%P protocol is a stateless and connectionless protocol )ecause each command is a reuest and is e*ecuted independentl,without an knowled"e of the reuests that were e*ecuted )efore it. 4n this protocol the communication "enerall takes placeover a %CP04P protocol.

$. 8&=-'hort for !ile %ransfer Protocol, theprotocolfor e*chan"in"filesover the 4nternetit uses the 4nternets %CP04Pprotocolsto ena)le data transfer. !%P is most commonl used to downloada file from a server usin" the 4nternet or touploada file to aserver (e."., uploadin" a e) pa"e file to a server. 4ts also commonl used to download pro"rams and other files to ourcomputer from other servers. ou need to lo"onto an !%P server. Iowever, pu)licl availa)le files are easil accessedusin"anonmous !%P.

O)+ectives of !%P were3

5. to promote sharin" of files (computer pro"rams and0or data,. to encoura"e indirect or implicit (via pro"rams use of remote computers,=. to shield a user from variations in file stora"e sstems amon" hosts, andH. to transfer data relia)l and efficientl.
http://compnetworking.about.com/od/networkprotocols/f/packet-switch.htmhttp://compnetworking.about.com/od/networkprotocols/f/packet-switch.htmhttp://compnetworking.about.com/od/networkprotocols/f/packet-switch.htmhttp://compnetworking.about.com/od/networkprotocolsip/g/ip_protocol.htmhttp://compnetworking.about.com/od/networkprotocolsip/g/ip_protocol.htmhttp://compnetworking.about.com/od/networkprotocolsip/g/ip_protocol.htmhttp://compnetworking.about.com/od/networkprotocolsip/g/ip_protocol.htmhttp://compnetworking.about.com/cs/basictcpip/g/bldef_tcpip.htmhttp://compnetworking.about.com/library/glossary/bldef-udp.htmhttp://compnetworking.about.com/od/networkprotocols/g/bldef_http.htmhttp://compnetworking.about.com/od/networkprotocols/g/bldef_http.htmhttp://compnetworking.about.com/od/networkprotocols/g/bldef_ftp.htmhttp://compnetworking.about.com/od/networkprotocols/g/bldef_arp.htmhttp://compnetworking.about.com/od/networkprotocols/g/bldef_arp.htmhttp://compnetworking.about.com/od/tcpip/g/bldef_icmp.htmhttp://compnetworking.about.com/od/tcpip/g/bldef_icmp.htmhttp://compnetworking.about.com/cs/routers/g/bldef_router.htmhttp://www.webopedia.com/TERM/P/protocol.htmlhttp://www.webopedia.com/TERM/W/World_Wide_Web.htmlhttp://www.webopedia.com/TERM/W/World_Wide_Web.htmlhttp://www.webopedia.com/TERM/W/Web_server.htmlhttp://www.webopedia.com/TERM/W/Web_server.htmlhttp://www.webopedia.com/TERM/B/browser.htmlhttp://www.webopedia.com/TERM/B/browser.htmlhttp://www.webopedia.com/TERM/P/protocol.htmlhttp://www.webopedia.com/TERM/P/protocol.htmlhttp://www.webopedia.com/TERM/P/protocol.htmlhttp://www.webopedia.com/TERM/F/file.htmlhttp://www.webopedia.com/TERM/F/file.htmlhttp://www.webopedia.com/TERM/F/file.htmlhttp://www.webopedia.com/TERM/I/internet.htmlhttp://www.webopedia.com/TERM/I/internet.htmlhttp://www.webopedia.com/TERM/T/TCP_IP.htmlhttp://www.webopedia.com/TERM/D/download.htmlhttp://www.webopedia.com/TERM/D/download.htmlhttp://www.webopedia.com/TERM/U/upload.htmlhttp://www.webopedia.com/TERM/U/upload.htmlhttp://www.webopedia.com/TERM/U/upload.htmlhttp://searchsecurity.techtarget.com/definition/logonhttp://searchsoa.techtarget.com/definition/anonymous-FTPhttp://searchsoa.techtarget.com/definition/anonymous-FTPhttp://searchsoa.techtarget.com/definition/anonymous-FTPhttp://compnetworking.about.com/od/networkprotocols/f/packet-switch.htmhttp://compnetworking.about.com/od/networkprotocolsip/g/ip_protocol.htmhttp://compnetworking.about.com/od/networkprotocolsip/g/ip_protocol.htmhttp://compnetworking.about.com/cs/basictcpip/g/bldef_tcpip.htmhttp://compnetworking.about.com/library/glossary/bldef-udp.htmhttp://compnetworking.about.com/od/networkprotocols/g/bldef_http.htmhttp://compnetworking.about.com/od/networkprotocols/g/bldef_ftp.htmhttp://compnetworking.about.com/od/networkprotocols/g/bldef_arp.htmhttp://compnetworking.about.com/od/tcpip/g/bldef_icmp.htmhttp://compnetworking.about.com/cs/routers/g/bldef_router.htmhttp://www.webopedia.com/TERM/P/protocol.htmlhttp://www.webopedia.com/TERM/W/World_Wide_Web.htmlhttp://www.webopedia.com/TERM/W/Web_server.htmlhttp://www.webopedia.com/TERM/B/browser.htmlhttp://www.webopedia.com/TERM/P/protocol.htmlhttp://www.webopedia.com/TERM/F/file.htmlhttp://www.webopedia.com/TERM/I/internet.htmlhttp://www.webopedia.com/TERM/T/TCP_IP.htmlhttp://www.webopedia.com/TERM/D/download.htmlhttp://www.webopedia.com/TERM/U/upload.htmlhttp://searchsecurity.techtarget.com/definition/logonhttp://searchsoa.techtarget.com/definition/anonymous-FTP


13/15

!%P works in the same wa asI%%Pfor transferrin" e) pa"es from a serverto a users )rowser and 'M%Pfortransferrin"electronic mailacross the 4nternet.

". &C=/=. %CP04P (%ransmission Control Protocol04nternet Protocol is the )asic communication lan"ua"e or protocolof the 4nternet. %CP04P is a two-laer pro"ram.

%he hi"her laer,&ransmission Control =roto"ol, is responsi)le for ensurin" that a messa"e or a file is

divided into smaller packets, num)ers the packets, and then forwards them individuall to the 4P pro"ramlaer to )e transmitted over the 4nternet. 2ecause a messa"e is divided into a num)er of packets, eachpacket can, if necessar, )e sent ) a different route across the 4nternet and therefore arrive in a differentorder than the order the were sent in. %he are received ) a %CP laer that reassem)les the packets intothe ori"inal messa"e. %hus %CP "uarantees deliver of data and also "uarantees that packets will )e

delivered in the same order in which the were sent. %CP is known as a connection-oriented protocol, whichmeans that a connection is esta)lished and maintained until such time as the messa"e or messa"es to )ee*chan"ed ) the application pro"rams at each end have )een e*chan"ed.

%he lower laer, nternet =roto"ol, handles theaddresspart of each packet so that data is transmitted from

one computer to another. $ach computer (known as a host on the 4nternet has at least one 4P addressthatuniuel identifies it from all other computers on the 4nternet. $ach packet of data contains )oth the senders4nternet address and the receivers address and is sent first to a"atewacomputer for routin". 4P is aconnectionless protocol, which means that there is no continuin" connection )etween the end points that arecommunicatin". $ach packet that travels throu"h the 4nternet is treated as an independent unit of datawithout an relation to an other unit of data.

A "atewa computer understands a small part of the 4nternet. %he "atewa computer reads the destination address andforwards the packet to an ad+acent "atewa that in turn reads the destination address and so forth across the 4nternet until one"atewa reco"ni/es the packet as )elon"in" to a computer within its immediate nei"h)orhood or domain.%hat "atewa thenforwards the packet directl to the computer whose address is specified.

d. #=/=== 3 Ma+orit of the people use telephone lines and modem to connect to the internet. %here are mainl two mainmodem protocols3

'84P3 'erial 8ine 4nternet Protocol. An old protocol, low in controls. 4t sends a frame composed onl of data to )e sent

followed ) an end of transmission character (the $#D character, theA'C44 codeof which is 56. A '84P frame lookslike this3

Data to )etransmitted

$#D

PPP3 PPP can )e defined as an encapsulation method for transmittin" multiple- protocol data"rams over point-to-point

links. PPP is a laered protocol startin" with the 8ink Control Protocol (8CP, for settin" up, confi"urin", andmonitorin" the connection to ensure that the connection remains relia)le. 4n addition, ) usin" #etwork ControlProtocols (#CPs, different network- laer protocols can )e used dnamicall. %he 4P Control Protocol (4PCP permitsthe transport of 4P packets over a PPP link.

4pansion of network proto"ols

>>- >ultipurpose nternet >ail 4tensions

#>&=- #imple >ail &ransfer =roto"ol

NN&= 3 Network News &ransfer =roto"ol

Gopher-%CP04Papplication laerprotocoldesi"ned for distri)utin", searchin", and retrievin" documents

over the4nternet.

,A#B ide Area 4nformation 'erverG Client server te*t searchin" sstem.

:=- &ser Data"ram Protocol

16. ,ireless/>o$ile "omputing,irelesstelecommunicationsis the transfer of information )etween two or more points that are not phsicall connected.ireless networks utili/e radio waves and0or microwaves to maintain communication channels )etween computers.

Advanta"es of wireless include mo)ilit and elimination of unsi"htl ca)les. Disadvanta"es of wireless include the potential for

radio interference due to weather, other wireless devices, or o)structions like walls. 4t encompasses various tpes of fi*ed,mo)ile, and porta)letwo-wa radios, cellular telephones, personal di"ital assistants(PDAs, and wireless networkin".Othere*amples of wireless technolo" include FP'units,Fara"e door openers, home entertainment sstem control )o*es- %E andECR remotes, wirelesscomputer peripherals(mouse, ke)oards, headphones,printers,radio receivers,satellitetelevision, )roadcast televisionand cordless telephones. ireless networks use i-!i (wireless fidelit technolo" for providin"network covera"e to offices, pu)lic places, and other small workplaces. A wireless access point device is used to provide wirefree network covera"e in the desi"nated area.

>o$ilerefers to the use of small and porta)le computin" device tpicall havin" a displa screen withtouchinput and0or aminiature ke)oard and wei"htin" less than pounds (:.65 k".%hese devices include laptops, note)ook PCs, ta)let PCs,palmtops, personal di"ital assistant (PDAs and other hand held devices. A radio-si"nalin" device is installed inside thesedevices for receivin" and transmittin" electronic data.

Feneral Packet Radio 'ervice (FPR' -- a packet-)ased wireless communication service that provides

continuous connection to the 4nternet for mo)ile phone and computer users
http://www.webopedia.com/TERM/H/HTTP.htmlhttp://www.webopedia.com/TERM/H/HTTP.htmlhttp://www.webopedia.com/TERM/S/server.htmlhttp://www.webopedia.com/TERM/S/SMTP.htmlhttp://www.webopedia.com/TERM/E/e_mail.htmlhttp://www.webopedia.com/TERM/E/e_mail.htmlhttp://searchsoftwarequality.techtarget.com/definition/layerhttp://searchsoftwarequality.techtarget.com/definition/layerhttp://searchunifiedcommunications.techtarget.com/definition/Internet-Protocolhttp://searchnetworking.techtarget.com/definition/addresshttp://searchnetworking.techtarget.com/definition/addresshttp://searchnetworking.techtarget.com/definition/addresshttp://searchcio-midmarket.techtarget.com/sDefinition/0,,sid183_gci212254,00.htmlhttp://searchwindevelopment.techtarget.com/sDefinition/0,,sid8_gci212381,00.htmlhttp://searchnetworking.techtarget.com/sDefinition/0,,sid7_gci212176,00.htmlhttp://searchnetworking.techtarget.com/sDefinition/0,,sid7_gci212176,00.htmlhttp://searchsoa.techtarget.com/sDefinition/0,,sid26_gci211987,00.htmlhttp://searchsoa.techtarget.com/sDefinition/0,,sid26_gci211987,00.htmlhttp://en.kioskea.net/contents/base/ascii.php3http://en.kioskea.net/contents/base/ascii.php3http://en.wikipedia.org/wiki/TCP/IPhttp://en.wikipedia.org/wiki/TCP/IPhttp://en.wikipedia.org/wiki/TCP/IPhttp://en.wikipedia.org/wiki/Application_layerhttp://en.wikipedia.org/wiki/Communications_protocolhttp://en.wikipedia.org/wiki/Communications_protocolhttp://en.wikipedia.org/wiki/Communications_protocolhttp://en.wikipedia.org/wiki/Internethttp://en.wikipedia.org/wiki/Internethttp://en.wikipedia.org/wiki/Telecommunicationhttp://en.wikipedia.org/wiki/Telecommunicationhttp://en.wikipedia.org/wiki/Two-way_radiohttp://en.wikipedia.org/wiki/Two-way_radiohttp://en.wikipedia.org/wiki/Mobile_phonehttp://en.wikipedia.org/wiki/Personal_digital_assistanthttp://en.wikipedia.org/wiki/Wireless_networkhttp://en.wikipedia.org/wiki/Wireless_networkhttp://en.wikipedia.org/wiki/Global_Positioning_Systemhttp://en.wikipedia.org/wiki/Garage_door_openerhttp://en.wikipedia.org/wiki/Garage_door_openerhttp://en.wikipedia.org/wiki/Mouse_(computing)http://en.wikipedia.org/wiki/Mouse_(computing)http://en.wikipedia.org/wiki/Keyboard_(computing)http://en.wikipedia.org/wiki/Headphonehttp://en.wikipedia.org/wiki/Headphonehttp://en.wikipedia.org/wiki/Radio_receiverhttp://en.wikipedia.org/wiki/Radio_receiverhttp://en.wikipedia.org/wiki/Radio_receiverhttp://en.wikipedia.org/wiki/Satellite_televisionhttp://en.wikipedia.org/wiki/Satellite_televisionhttp://en.wikipedia.org/wiki/Satellite_televisionhttp://en.wikipedia.org/wiki/Broadcast_televisionhttp://en.wikipedia.org/wiki/Telephonehttp://en.wikipedia.org/wiki/Touchscreenhttp://en.wikipedia.org/wiki/Touchscreenhttp://en.wikipedia.org/wiki/Touchscreenhttp://searchmobilecomputing.techtarget.com/definition/GPRShttp://searchmobilecomputing.techtarget.com/definition/GPRShttp://www.webopedia.com/TERM/H/HTTP.htmlhttp://www.webopedia.com/TERM/S/server.htmlhttp://www.webopedia.com/TERM/S/SMTP.htmlhttp://www.webopedia.com/TERM/E/e_mail.htmlhttp://searchsoftwarequality.techtarget.com/definition/layerhttp://searchunifiedcommunications.techtarget.com/definition/Internet-Protocolhttp://searchnetworking.techtarget.com/definition/addresshttp://searchcio-midmarket.techtarget.com/sDefinition/0,,sid183_gci212254,00.htmlhttp://searchwindevelopment.techtarget.com/sDefinition/0,,sid8_gci212381,00.htmlhttp://searchnetworking.techtarget.com/sDefinition/0,,sid7_gci212176,00.htmlhttp://searchsoa.techtarget.com/sDefinition/0,,sid26_gci211987,00.htmlhttp://en.kioskea.net/contents/base/ascii.php3http://en.wikipedia.org/wiki/TCP/IPhttp://en.wikipedia.org/wiki/Application_layerhttp://en.wikipedia.org/wiki/Communications_protocolhttp://en.wikipedia.org/wiki/Internethttp://en.wikipedia.org/wiki/Telecommunicationhttp://en.wikipedia.org/wiki/Two-way_radiohttp://en.wikipedia.org/wiki/Mobile_phonehttp://en.wikipedia.org/wiki/Personal_digital_assistanthttp://en.wikipedia.org/wiki/Wireless_networkhttp://en.wikipedia.org/wiki/Global_Positioning_Systemhttp://en.wikipedia.org/wiki/Garage_door_openerhttp://en.wikipedia.org/wiki/Mouse_(computing)http://en.wikipedia.org/wiki/Keyboard_(computing)http://en.wikipedia.org/wiki/Headphonehttp://en.wikipedia.org/wiki/Radio_receiverhttp://en.wikipedia.org/wiki/Satellite_televisionhttp://en.wikipedia.org/wiki/Satellite_televisionhttp://en.wikipedia.org/wiki/Broadcast_televisionhttp://en.wikipedia.org/wiki/Telephonehttp://en.wikipedia.org/wiki/Touchscreenhttp://searchmobilecomputing.techtarget.com/definition/GPRS


14/15

$nhanced Data F'M $nvironment ($DF$ -- a faster version of the Flo)al 'stem for Mo)ile (F'M

wireless service

&niversal Mo)ile %elecommunications 'stem (&M%' -- a )road)and, packet-)ased sstem offerin" a

consistent set of services to mo)ile computer and phone users no matter where the are located in the world

ireless Application Protocol (AP -- a set of communication protocols to standardi/e the wa that wireless

devices, such as cellular telephones and radio transceivers, can )e used for 4nternet access

i-Mode -- the worlds first >smart phone> for e) )rowsin", first introduced in ?apanG provides color and video

over telephone sets

ireless can )e divided into3

!i*ed wireless -- the operation of wireless devices or sstems in homes and offices, and in particular,

euipment connected to the 4nternet via speciali/ed modems

Mo)ile wireless -- the use of wireless devices or sstems a)oard motori/ed, movin" vehiclesG e*amples

include the automotive cell phone and PC'(personal communications services

Porta)le wireless -- the operation of autonomous, )atter-powered wireless devices or sstems outside the

office, home, or vehicleG e*amples include handheld cell phones and PC' units

4R wireless -- the use of devices that conve data via 4R (infrared radiationG emploed in certain limited-ran"e

communications and control sstems,ireless/>o$ile Computing &e"hnologies

a Glo$al #%stem for >o$ile Communi"ation (G#> - a di"ital mo)ile telephone sstem used in $urope, Australia. Africa,Asia and other parts of the worldG the de facto wireless telephone standard in $urope. F'M uses narrow)and %DMA(%imeDivision Multiple Access which allows ei"ht simultaneous calls on the same radio freuenc. 4t is used in di"ital cellular andPC'-)ased sstems. F'M is also the )asis for 4nte"rated Di"ital $nhanced #etwork(4D$#. %he ke element in F'M mo)ilephones is the '4M('u)scri)er 4dentit Module card which is a small remova)le chip that "ives a cellular device is uniue phonenum)er.

$ C>A(Code-ivision >ultiple A""ess- 4t is a techniue used for di"ital communication, and wireless technolo" inparticular, that involves multiple*in"(which allows numerous si"nals to occup a sin"le transmissionchannel, optimi/in" the useof availa)le)andwidth.. 4t refers to an of several protocols used in so-called second-"eneration (F and third-"eneration(=F wirelesscommunications %he technolo" is used in ultra-hi"h-freuenc (&I!cellular telephonesstems in the 9::-MI/and 5.6-FI/ )ands. CDMA emplos analo"-to-di"ital conversion (ADC in com)ination with spread spectrumtechniues.Iere data is sent in small pieces over a num)er of discrete freuencies availa)le for use. $ach user1s si"nal is spread over theentire )andwidth ) uniue spreadin" code. At the receiver end, the same uniue code is used to recover the si"nal.

" ,(,ireless in lo"al loop- CDMA stands for Code Division Multiple Access. 4t is a techniue used for di"italcommunication, and wireless technolo" in particular, that involves multiple*in"(which allows numerous si"nals to occup asin"le transmissionchannel, optimi/in" the use of availa)le)andwidth.. 4t refers to an of several protocols used in so-calledsecond-"eneration (F and third-"eneration (=Fwirelesscommunications %he technolo" is used in ultra-hi"h-freuenc(&I!cellular telephonesstems in the 9::-MI/and 5.6-FI/ )ands. CDMA emplos analo"-to-di"ital conversion (ADC incom)ination with spread spectrumtechniues. Iere data is sent in small pieces over a num)er of discrete freuenciesavaila)le for use. $ach user1s si"nal is spread over the entire )andwidth ) uniue spreadin" code. At the receiver end, thesame uniue code is used to recover the si"nal.

d G and G -=F(%hird Feneration or &M%'(&niversal Mo)ile %elecommunications 'stem mo)ile communicationstechnolo" is a )road)and, packet-)ased transmission of te*t, di"iti/ed voice, video, and multimedia at data rates up to andpossi)l hi"her than me"a)its per second(M)ps, offerin" a consistent set of services to mo)ile computer and phone users nomatter where the are located in the world. =F can work over wireless air interfaces such as F'M, %DMA and CDMA.G 3$nhanced data for "lo)al evolution ($DF$ is a radio )ased hi"h-speed mo)ile data standard, intended to ena)lesecond-"eneration "lo)al sstem for mo)ile communication (F'M and time division multiple access (%DMA networks totransmit multimedia applications such as streamin" television, audio and video to mo)ile phones at speeds up to =9H J)ps. Asit was initiall developed +ust for F'M sstems, it has also )een called F'M=9H. $ricsson intended the technolo" for thosenetwork operators who failed to win spectrum auctions for third-"eneration networks to allow hi"h-speed data transmission.

e #># 3'hort Messa"e 'ervice is also often referred to as te*tin", sendin" te*t messa"es or te*t messa"in". %he serviceallows for short te*t messa"es to and from a mo)ile phone, fa* or e). 4ncludin" spaces, te*t messa"es traditionall can1t

e*ceed 57: characters. 'M' messa"es often use %6 predictive technolo".%he acronm %6 stands for %e*t on 6 kes. %6predictive te*tin" makes'M' messa"in"faster especiall for non-N$R%cell phones without full ke)oards.MM'(Multimedia Messa"in" 'ervice, which is often used to send pictures, e*tends upon 'M' and allows for lon"er contentlen"ths.

f mailB $lectronic Mail is a method of e*chan"in" di"ital messa"es from an author to one or more recipients. Modern emailoperates across the 4nternetor other computer networks. %odas email sstems are )ased on astore-and-forwardmodel.$mailserversaccept, forward, deliver and store messa"es. #either the users nor their computers are reuired to )e onlinesimultaneouslG the need connect onl )riefl, tpicall to anemail server,for as lon" as it takes to send or receive messa"es.Computers use the %CP04P protocol suite to send email messa"es in the form of packets. An email messa"e consists of threecomponents, the messa"e envelope, the messa"e header, and the messa"e )od. %he messa"e header contains controlinformation, includin", minimall, an ori"inators email addressand one or more recipient addresses. &suall descriptiveinformation is also added, such as a su)+ect header field and a messa"e su)mission date0time stamp.

Advantages of mail

1. Cheap.Once ou1re online, there is no further e*pense.
http://searchmobilecomputing.techtarget.com/definition/EDGEhttp://searchmobilecomputing.techtarget.com/definition/UMTShttp://searchmobilecomputing.techtarget.com/definition/WAPhttp://searchmobilecomputing.techtarget.com/definition/WAPhttp://searchnetworking.techtarget.com/definition/i-Modehttp://searchmobilecomputing.techtarget.com/definition/fixed-wirelesshttp://searchnetworking.techtarget.com/definition/PCShttp://searchmobilecomputing.techtarget.com/definition/IR-wirelesshttp://searchmobilecomputing.techtarget.com/definition/GSMhttp://www.wisegeek.com/what-is-multiplexing.htmhttp://searchdatacenter.techtarget.com/definition/channelhttp://searchdatacenter.techtarget.com/definition/channelhttp://searchenterprisewan.techtarget.com/definition/bandwidthhttp://searchenterprisewan.techtarget.com/definition/bandwidthhttp://searchenterprisewan.techtarget.com/definition/bandwidthhttp://searchtelecom.techtarget.com/definition/3Ghttp://searchtelecom.techtarget.com/definition/3Ghttp://searchmobilecomputing.techtarget.com/definition/wirelesshttp://searchmobilecomputing.techtarget.com/definition/wirelesshttp://searchnetworking.techtarget.com/definition/UHFhttp://searchnetworking.techtarget.com/definition/UHFhttp://searchmobilecomputing.techtarget.com/definition/cellular-telephonehttp://searchmobilecomputing.techtarget.com/definition/cellular-telephonehttp://searchnetworking.techtarget.com/definition/MHzhttp://searchnetworking.techtarget.com/definition/spread-spectrumhttp://www.wisegeek.com/what-is-multiplexing.htmhttp://www.wisegeek.com/what-is-multiplexing.htmhttp://searchdatacenter.techtarget.com/definition/channelhttp://searchdatacenter.techtarget.com/definition/channelhttp://searchenterprisewan.techtarget.com/definition/bandwidthhttp://searchenterprisewan.techtarget.com/definition/bandwidthhttp://searchenterprisewan.techtarget.com/definition/bandwidthhttp://searchtelecom.techtarget.com/definition/3Ghttp://searchtelecom.techtarget.com/definition/3Ghttp://searchmobilecomputing.techtarget.com/definition/wirelesshttp://searchmobilecomputing.techtarget.com/definition/wirelesshttp://searchnetworking.techtarget.com/definition/UHFhttp://searchnetworking.techtarget.com/definition/UHFhttp://searchmobilecomputing.techtarget.com/definition/cellular-telephonehttp://searchmobilecomputing.techtarget.com/definition/cellular-telephonehttp://searchnetworking.techtarget.com/definition/MHzhttp://searchnetworking.techtarget.com/definition/MHzhttp://searchnetworking.techtarget.com/definition/spread-spectrumhttp://cellphones.about.com/od/phoneglossary/g/t9predictivetext.htmhttp://cellphones.about.com/od/phoneglossary/g/t9predictivetext.htmhttp://cellphones.about.com/od/phoneglossary/g/smstextmessage.htmhttp://cellphones.about.com/od/phoneglossary/g/smstextmessage.htmhttp://cellphones.about.com/od/phoneglossary/g/qwertydefinition.htmhttp://cellphones.about.com/od/phoneglossary/g/qwertydefinition.htmhttp://cellphones.about.com/od/textmessaging/tp/besttextmessaging.htmhttp://cellphones.about.com/od/textmessaging/tp/besttextmessaging.htmhttp://cellphones.about.com/od/phoneglossary/g/mmspicturemessaging.htmhttp://en.wikipedia.org/wiki/Internethttp://en.wikipedia.org/wiki/Computer_networkhttp://en.wikipedia.org/wiki/Store-and-forwardhttp://en.wikipedia.org/wiki/Store-and-forwardhttp://en.wikipedia.org/wiki/Computer_serverhttp://en.wikipedia.org/wiki/Computer_serverhttp://en.wikipedia.org/wiki/E-mail_serverhttp://en.wikipedia.org/wiki/E-mail_serverhttp://en.wikipedia.org/wiki/E-mail_serverhttp://en.wikipedia.org/wiki/Email_addresshttp://searchmobilecomputing.techtarget.com/definition/EDGEhttp://searchmobilecomputing.techtarget.com/definition/UMTShttp://searchmobilecomputing.techtarget.com/definition/WAPhttp://searchnetworking.techtarget.com/definition/i-Modehttp://searchmobilecomputing.techtarget.com/definition/fixed-wirelesshttp://searchnetworking.techtarget.com/definition/PCShttp://searchmobilecomputing.techtarget.com/definition/IR-wirelesshttp://searchmobilecomputing.techtarget.com/definition/GSMhttp://www.wisegeek.com/what-is-multiplexing.htmhttp://searchdatacenter.techtarget.com/definition/channelhttp://searchenterprisewan.techtarget.com/definition/bandwidthhttp://searchtelecom.techtarget.com/definition/3Ghttp://searchmobilecomputing.techtarget.com/definition/wirelesshttp://searchnetworking.techtarget.com/definition/UHFhttp://searchmobilecomputing.techtarget.com/definition/cellular-telephonehttp://searchnetworking.techtarget.com/definition/MHzhttp://searchnetworking.techtarget.com/definition/spread-spectrumhttp://www.wisegeek.com/what-is-multiplexing.htmhttp://searchdatacenter.techtarget.com/definition/channelhttp://searchenterprisewan.techtarget.com/definition/bandwidthhttp://searchtelecom.techtarget.com/definition/3Ghttp://searchmobilecomputing.techtarget.com/definition/wirelesshttp://searchnetworking.techtarget.com/definition/UHFhttp://searchmobilecomputing.techtarget.com/definition/cellular-telephonehttp://searchnetworking.techtarget.com/definition/MHzhttp://searchnetworking.techtarget.com/definition/spread-spectrumhttp://cellphones.about.com/od/phoneglossary/g/t9predictivetext.htmhttp://cellphones.about.com/od/phoneglossary/g/smstextmessage.htmhttp://cellphones.about.com/od/phoneglossary/g/qwertydefinition.htmhttp://cellphones.about.com/od/textmessaging/tp/besttextmessaging.htmhttp://cellphones.about.com/od/phoneglossary/g/mmspicturemessaging.htmhttp://en.wikipedia.org/wiki/Internethttp://en.wikipedia.org/wiki/Computer_networkhttp://en.wikipedia.org/wiki/Store-and-forwardhttp://en.wikipedia.org/wiki/Computer_serverhttp://en.wikipedia.org/wiki/E-mail_serverhttp://en.wikipedia.org/wiki/Email_address


15/15

. as% to referen"e.'ent and received messa"es and attachments can )e stored safel, lo"icall and relia)l.=. as% to use.Once ou1re set up, sendin" and receivin" messa"es is simple. %hat "oes for a host of other email functions.

Data stora"e and contacts can )e accessed uickl and easil.H. as% to prioriti+e.4ncomin" messa"es have su)+ect lines that mean ou can delete without openin".. 8ast.$mail is ) far the fastest form of written communication.7. Glo$al.e) )ased email means ou can access our messa"es anwhere online.@. Good for the planet.Reduces use of paper for "eneral and routine communication.9. nfo at %our fingertips.'torin" data online means less lar"e, space takin" file ca)inets, folders and shelves. ou can

access information far uicker if ou learn how to use email this wa.

6. everage. 'end the same messa"e to an num)er of people. Adaptations are simple, too. 4fou have a product orservice to sell, email is an effective medium to "et our messa"e out.

isadvantages of mail1. motional responses. 'ome emails cause upset or an"er. A repl in the heat of the moment can1t )e retracted.2. nformation overload. %oo man people send too much information

3. a"ks the personal tou"h. 'ome thin"s are )est left untped. $mail will never )eat a hand written card or letter whenit comes to relationships.

4. >isunderstandings.$mails from people who don1t take the time to read what the write )efore clickin" ;send1. %imeis wasted, either to clarif or, worse, actin" on a misinterpretation of the messa"e.

5. #pam. Man people send unwanted emails to others. %hese are called spam mails. 4t takes a lot of time to filterout the unwanted emails from those that are reall important.

6. ,astage of time. Over checkin" messa"es is time wasted on low value, passive activit.

7. Eiruses. $mails ma carr viruses. %hese are small pro"rams that harm our computer sstem. %he can read outour email address )ook and send themselves to a num)er of people around the world.

8.$mails cannot reall )e used for official )usiness documents. %he ma )e lost and ou cannot si"n them.

6. our mail)o* ma "et flooded with emails after a certain time so ou have to empt it from time to time.

g Eoi"e >ailrefers toe-mailsstems thatsupportaudio. &serscan leave spoken messa"es for one another and listen to themessa"es ) e*ecutin" the appropriatecommandin the e-mail sstem.

h Chatrefers to real-timecommunication )etween twousersvia computer.Once a chat has )een initiated, either user canenterte*t) tpin" on theke)oardand the entered te*t will appear on the other users monitor.

i Eideo Conferen"ing 3 4t refers to conductin" aconference)etween two or more participants at different sites )usin"computernetworksto transmit audio and videodata. $ach participant has a video camera, microphone, and speakersmounted on his or her computer. As the two participants speak to one another, their voices are carried over the network anddelivered to the others speakers, and whatever ima"es appear in front of the video camera appear in awindowon the otherparticipants monitor. Multipoint videoconferencin" allows three or more participants to sit in avirtualconference room and

communicate as if the were sittin" ri"ht ne*t to each other.

19. nternetworking terms and "on"epts

,orld ,ide ,e$. A "atewa is a networkpoint that acts as an entrance to another network. %he main +o) of a "atewa is toconnect dissimilar networks. 4t esta)lishes an intelli"ent connection )etween a local network and e*ternal network withcompletel different structures. 4t is capa)le of performin" )oth data translation and protocol conversion (e.". $thernet 8A# to'#A
http://www.webopedia.com/TERM/E/e_mail.htmlhttp://www.webopedia.com/TERM/S/system.htmlhttp://www.webopedia.com/TERM/S/support.htmlhttp://www.webopedia.com/TERM/U/user.htmlhttp://www.webopedia.com/TERM/E/execute.htmlhttp://www.webopedia.com/TERM/C/command.htmlhttp://www.webopedia.com/TERM/R/real_time.htmlhttp://www.webopedia.com/TERM/R/real_time.htmlhttp://www.webopedia.com/TERM/R/real_time.htmlhttp://www.webopedia.com/TERM/U/user.htmlhttp://www.webopedia.com/TERM/U/user.htmlhttp://www.webopedia.com/TERM/U/user.htmlhttp://www.webopedia.com/TERM/C/computer.htmlhttp://www.webopedia.com/TERM/C/computer.htmlhttp://www.webopedia.com/TERM/T/text.htmlhttp://www.webopedia.com/TERM/T/text.htmlhttp://www.webopedia.com/TERM/K/keyboard.htmlhttp://www.webopedia.com/TERM/K/keyboard.htmlhttp://www.webopedia.com/TERM/M/monitor.htmlhttp://www.webopedia.com/TERM/C/conference.htmlhttp://www.webopedia.com/TERM/C/conference.htmlhttp://www.webopedia.com/TERM/C/computer.htmlhttp://www.webopedia.com/TERM/C/computer.htmlhttp://www.webopedia.com/TERM/N/network.htmlhttp://www.webopedia.com/TERM/N/network.htmlhttp://www.webopedia.com/TERM/V/video.htmlhttp://www.webopedia.com/TERM/V/video.htmlhttp://www.webopedia.com/TERM/D/data.htmlhttp://www.webopedia.com/TERM/D/data.htmlhttp://www.webopedia.com/TERM/W/window.htmlhttp://www.webopedia.com/TERM/W/window.htmlhttp://www.webopedia.com/TERM/W/window.htmlhttp://www.webopedia.com/TERM/M/monitor.htmlhttp://www.webopedia.com/TERM/V/virtual.htmlhttp://www.webopedia.com/TERM/V/virtual.htmlhttp://searchnetworking.techtarget.com/sDefinition/0,,sid7_gci212644,00.htmlhttp://searchnetworking.techtarget.com/sDefinition/0,,sid7_gci212644,00.htmlhttp://www.webopedia.com/TERM/E/e_mail.htmlhttp://www.webopedia.com/TERM/S/system.htmlhttp://www.webopedia.com/TERM/S/support.htmlhttp://www.webopedia.com/TERM/U/user.htmlhttp://www.webopedia.com/TERM/E/execute.htmlhttp://www.webopedia.com/TERM/C/command.htmlhttp://www.webopedia.com/TERM/R/real_time.htmlhttp://www.webopedia.com/TERM/U/user.htmlhttp://www.webopedia.com/TERM/C/computer.htmlhttp://www.webopedia.com/TERM/T/text.htmlhttp://www.webopedia.com/TERM/K/keyboard.htmlhttp://www.webopedia.com/TERM/M/monitor.htmlhttp://www.webopedia.com/TERM/C/conference.htmlhttp://www.webopedia.com/TERM/C/computer.htmlhttp://www.webopedia.com/TERM/N/network.htmlhttp://www.webopedia.com/TERM/V/video.htmlhttp://www.webopedia.com/TERM/D/data.htmlhttp://www.webopedia.com/TERM/W/window.htmlhttp://www.webopedia.com/TERM/M/monitor.htmlhttp://www.webopedia.com/TERM/V/virtual.htmlhttp://searchnetworking.techtarget.com/sDefinition/0,,sid7_gci212644,00.html

Communication and network concepts.doc

Documents

Transcript of Communication and network concepts.doc