network 2014 cbse class 12

8/10/2019 Network 2014 CBSE CLASS 12

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Networking Concepts

What is Network?

A network is any collection of independent computers that communicates with one another over a sha

network medium.When computers are joined in a network, people can share files and peripherals such as mode

printers, backup drives or CD-ROM drives. Each computer on the network is called a node.Advantages for Networking

. Resource sharin! "files and peripherals

#. $mprovin! Communication

%. &ccess to Remote Database

Disadvantages of Networking. Threat to data' & computer network ma( be used b( unauthori)ed users to steal or corrupt the data and e

to deplo( computer virus or worms on the network.

#. Difficult to set up' *ettin! up a lar!e network ma( turn out to be a difficult task.

Evaluation of Networking

In 1!, the "epartment of "efense +DOD of nited *tates of &merica started a network called A#$AN

&Advanced #esearch $ro'ects Administration Network. $t was started with one computer in California and t

computers in tah. ater, the militar( allowed universities to join the network for sharin! the hardware and softwresources. /hen it !rew bi!!er and !ave birth to the present da( ver( popular $nternet.

Internet

$t is an interconnection between several computers of different t(pe belon!in! to various networks all over the wo

Intranet

$ntranet is an interconnected network within an or!ani)ation that uses web technolo!ies for the sharin! of informainternall(.

Interspace

$t is a client/server software programthat allows multiple users to communicate online with real time audio, v

and te0t chat in d(namic %D environment. $t provides the most advanced form of communication available in

$nternet toda(.

#e(uirements of a Network

1ver( network includes' &t least two computers " *erver or Client workstation

2etwork $nterface Card +2$C

& communication medium " wired or wireless

2etwork operatin! s(stem software such as Microsoft Windows 2/ or #333, 2ovell 2etWare, ni0

inu0.

Network %erminologies

. Nodes &Workstation)*& computer becomes a node +also called a workstation as soon as it is attached

network.

#. +erver' & computer that facilitates sharin! of data, software and hardware resources on the network is knoas the server. & network can have more than one server. 1ach server has a uni4ue name b( which

identified b( all the nodes on the network. *erver can be of two t(pes'

a "edicated' /hese are !enerall( used on bi! network installations where one computer is reserved

server5s job. $t helps all nodes access data, software and hardware resources.


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b Non,dedicated' /he small networks usin! such a server are known as 6eer to 6eer networks. &lso

a network there ma( be several servers that allow workstations to share specific resources -e0ample a file server which takes care of files related re4uests, a printer server takin! care of prin

re4uirements and a modem server that helps !roup of users to use a modem.

%. Network Interface -nit &NI-)*$t is a device attached to each of the workstations and the server which hto establish communication between the server and workstations. $t is also known as %erminal Access $

&%A$)or Network Interface card &NIC)./he 2$C manufacturer assi!ns a uni4ue ph(sical address to e

2$C card and this ph(sical address is known as the M&C +Media &ccess Control address.

Network +witching %echni(ues

*witchin! techni4ues are used to efficientl( transmit data across the network. /he two t(pes of switchin! techni4

that provide communication between two computers on a network are' Circuit SwitchingandPacket Switching

Circuit switching'

$t is the simplest method of data communication in which a dedicated physical pathis established between

source computer and destination computer e.!., /elephone network where the communication path is dedicated tocaller and the called part( for the duration of the telephone call.

$acket switching'$nformation on the $nternet is transmitted in packets. sin! the /C6 protocol, a sin!le lar!e messa!e is divided in

se4uence of packets of si)e limits from #7 to 839: b(tes. 1ach packet has the address of sender and destinat

sin! the $6 protocol, the packets are passed from one network to another till the( reach their destination. &tdestination, the /C6 software reassembles the packets into the complete messa!e. $f an( packets are lost or dama

a re4uest is sent to retransmit the same messa!e. $t is not necessar( for all the packets in a messa!e to take ident

route.

%ypes of Network

& network can be a small !roup of same t(pe of 6Cs that have been linked to!ether in a small room or a few hund

computers of different t(pes spread around the world which have been linked to!ether to e0chan!e informat/hus, network can var( widel( in their si)e and !eo!raphical area. /hese are'

6ersonal &rea 2etwork +6&2

ocal &rea 2etwork +&2 Metropolitan &rea 2etwork +M&2

Wide &rea 2etwork +W&2

$AN &$ersonal

Area Network)*

AN &ocal Area

Network)*

/AN &/etropolitan

Area Network)*

WAN &Wide Area

Network)*

& 6&2 is a network

of Communicatin!devices +Computer,

6hone, M6%;M68

6la(er, Camera etc.

in the pro0imit( of

& &2 is a network of

computin!;Communicatin!devices in a room, buildin!,

or campus. $t can cover an

area of a few meters to a

few kilometres radius. &

& M&2 is a network of

computin!;communicatin!devices within a cit(. $t

can cover an area of a few

kilometres to a few

hundred kilometres radius.

& W&2 is a network of

computin!;communicatin!devices crossin! the limits o

a cit(, countr(, or continent.

can cover an area of over

hundreds of kilometre radiu

#


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an individual. $t cancover an area of a

few meters radius.

When (ou have totransfer son!s from

one cell phone to

another, (ou set up a6&2 of two phones.

When files aretransferred from a

6C to an M6%pla(er, a 6&2 is set

up between the two.

/here can also bemultiple devices in

6&2. & 6&2 can be

set up usin! !uidedmedia +*< cable

or un!uided media

+


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Attenuation' When an analo! si!nal travels a lon! distance it loses its stren!th. &mplifiers are used to increase

stren!th.

"istortion' 2oise si!nals interfere with the actual si!nal and distort it. Repeaters are used to re!enerate a disto

si!nal.

/odem' $t is a device which converts di!ital si!nals to analo! for transmission over analo! transmission facilsuch as telephone lines and vice versa.

%ransmission /edia or Communication channels

& communication channel is the path for transmission between two or more points. $ts purpose is to carr( messafrom one location to another location. /he( are classified as'

/wisted pair cable

Coa0ial cables

Optical fiber

Microwave transmission

Radio wave transmission

*atellite transmission

$nfrared transmission

Wired /edia

%wisted $air Cale Co,a2ial cale &or coa2) 3ptical 4ier cale

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/his is probabl( the most widel(used cable for creatin! small

computer networks. $t contains

four twisted pairs covered in anouter shield. /hese pairs are

colour coded. &n RA-8B

connecter is used to connect thiscable to a computer.

$t is of two t(pes'. *hielded /wisted 6air +*/6

Cable.#. nshielded /wisted 6air

+/6 Cable.

/he */6 cable comes withshieldin! of the individual pairs

of wires which protects it from

e0ternal interference andcrosstalk.

& coa0ial cable consists of twoconductors that share a common

a0is. /he inner conductor is a

strai!ht wire and the outerconductor is a shield that mi!ht be

braided or a foil.

$t can be of two t(pes'. /hicknet

#. /hinnet

/hicknet is thicker and its cablese!ment can be upto B33 metres

lon! and thinnet is thinner and its

cable se!ment can be upto 7Bmetres.

Advantages*

. $t is capable of carr(in! asi!nal over lon! distances

without amplification.

#. $t is simple, low wei!ht,eas( to install and eas( to

maintain.

%. $t is an ade4uate and leaste0pensive medium for low

speed +up to 3 mbps

applications where the distance

between the nodes is relativel(small.

"isadvantages*

. $t can easil( pick up noisesi!nals.

#.


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#adio Wave

%ransmission

/icro Wave

%ransmission

Infrared Wave

%ransmission

0luetooth

%ransmission

+atellite ink

?re4uenc( ran!e of

% >@) to %=@)

?re4uenc( ran!e of

%33M@) +3.% =@) to%33 =@). /his ran!e

has some overlappin!

portion +3.%=@) -%=@) with radio

waves

?re4uenc( ran!e

of %33 =@) to833 /@)

?re4uenc(

ran!e of #.83#=@) to #.873

=@)

Micro wave fre4uenc(

bands used for uplinkvar( from .: =@) to %3.

=@) and that for

downlink varies from.B=@) to #3.3=@).

Radio waves cantravel lon! distances

and can penetrate

buildin!s easil(./hese waves are

Omni-directional, so

the transmittin! andreceivin! antennas

need not be ali!ned.

$t offers ease ofcommunication over

difficult terrain

Microwaves travel instrai!ht lines and

cannot penetrate an(

solid object. /hetransmission is in

strai!ht lines so the

transmittin! andreceivin! antennas

need to be properl(

ali!ned + line of si!httransmission

$t is a line ofsi!ht

transmission.

/he waves donot cross an(

solid object in

between &t atime onl( two

devices can

communicatetherefore

information

passed to one

device is notleaked to

another device.

ine of si!htbetween

communicatin

! devices isnot re4uired


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etc. $t is used b(policemen and

securit( personals

etc.

Cordless mouse,and $ntrusion

detectors.

Advantages

1. $t is eas( to

communicate

throu!h radio

waves indifficult terrains

since there is no

need of di!!in!and la(in!

cables.

2. Radio waves can

travel throu!h

lon! distances inall directions.

&lso the( can

easil( passthrou!h

obstacles like a

buildin! so the(can be used for

both indoor and

outdoor

communication.

Advantages

. Microwavetransmission does not

re4uire the e0pense of

la(in! cables#. $t can carr( #B333voice channels at the

same time.

%. *ince no cables areto be laid down so it

offers ease of

communication overdifficult terrains like

hill( areas.

Advantages

. *ince it ishavin! short

ran!e of

communicationhence it isconsidered to be

a secure mode

of/ransmission.

#. $t is 4uite

ine0pensivetransmission

medium.

Can be

passwordprotected

Advantages

. *atellitecommunication is ver(

economical keepin! in

mind the fact that the areacovered throu!h satellitetransmission is 4uite

lar!e. ?or e.!., satellites

used for nationaltransmission are visible

from all parts of the

countr(.#. /ransmission and

reception costs are

independent of thedistance between the two

points.

"isadvantages

. $t is susceptible toweather effects like

rain, thunderstorm

etc.#. Data transmitted

throu!h radio waves

is not secure.

"isadvantages

. *i!nals becomeweak after travellin! a

certain distance and so

re4uire amplification./o overcome this

problem, repeaters are

used at re!ular

intervals +#B-%3 kms./he data si!nals are

received, amplified

and then etransmitted./his makes it a ver(

e0pensive mode of

communication#. $nstallation and

maintenance of

microwave links turnsout be a ver(

e0pensive affair.

%. /he transmission is

affected b( weatherconditions like rain,

thunderstorms etc.

"isadvantages

. $t can onl( beused for short

ran!e

communication.#. $nfrared wave

transmission

cannot pass

throu!hobstructions like

walls, buildin!s

etc.

*low data

transfer rate+up to Mbps.

"isadvantages

. 6lacin! the satellite intits orbit involves ver(

hi!h cost.

#. *ince si!nals sent to asatellite are broadcasted t

all receivers, so necessar(

securit( measures have to

be taken to preventunauthori)ed tamperin! o

data.

%. /ransmission isaffected b( weather

conditions like rain,

thunderstorm etc.


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Network %opology

$t refers to the !eometrical arran!ement of nodes in a local area network +&2.

/he network topolo!ies are'

0us %opology +tar %opology %ree %opology

$n bus topolo!( all the nodes are

connected to a main cable called

backbone. $f an( node has to send someinformation to an( other node, it sends

the si!nal to the backbone. /he si!nal

travels throu!h the entire len!th of thebackbone and is received b( the node

for which it is intended. & small device

called terminator is attached at each endof the backbone. When the si!nal

reaches the end of backbone, it is

absorbed b( the terminator and the

backbone !ets free to carr( anothersi!nal. /his prevents the reflection of

si!nal back on the cable and hence

eliminates the chances of si!nal

interference.

$n star topolo!( each node is

directl( connected to a

hub;switch. $f an( node has tosend some information to an(

other node, it sends the si!nal to

the hub;switch. /his si!nal isthen broadcast +in case of a

hub to all the nodes but is

accepted b( the intendednode+s. $n the case of a switch

the si!nal is sent onl( to the

intended node+s. *tar topolo!(

!enerall( re4uires more cablethan bus topolo!(.

/ree topolo!( is a combination

bus and star topolo!ies. $t is us

to combine multiple star topolo!networks. &ll the stars a

connected to!ether like a bus. /h

bus-star h(brid approach supporfuture e0pandabilit( of the networ

Advantages

i *ince there is a sin!le common data

path connectin! all the nodes, the bus

topolo!( uses a ver( short cable len!th

which considerabl( reduces theinstallation cost.

ii /he linear architecture is ver( simple

and reliable.iii &dditional nodes can be easil(

connected to the e0istin! bus network at

an( point alon! the len!th of thetransmission medium.

"isadvantages

i ?ault detection and isolation is

difficult. /his is because control of the

network is not centrali)ed in an(

particular node. $f a node is fault( on thebus, detection of fault ma( have to be

performed at man( points on the

Advantages

i ?ailure of a sin!le connection

does not affect the entire

network. $t just involves

disconnectin! one node from anotherwise full( functional

network. /his also helps in eas(

reconfi!uration of the network.ii ?ault detection is easier.

iii &ccess protocols bein! used

in a *tar network are ver(simple since the central node

has the control of the

transmission medium for datatransmission

"isadvantages i *ince ever(

node is directl( connected tothe centre, so lar!e amount of

cable is needed which increases

Advantages

. $t offers eas( wa( of netwo

e0pansion

#. 1ven if one network +star fai

the other networks remaconnected and workin!.

"isadvantages

. $t can be used in an

or!ani)ation of hierarchical

structure.

7


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network. /he fault( node has then to berectified at that connection point.

ii $f the central bus len!th becomes too

lon!, then repeaters mi!ht have to beused to amplif( the si!nal. /he use of

repeaters makes reconfi!uration

necessar(.iii *ince each node is directl(

connected to the central bus, so there hasto be some wa( of decidin! who can use

the network at an( !iven time.

the installation cost of thenetwork.

ii /he entire network is

dependent on the central node.$f the central node fails the

entire network !oes down.

Network "evices

/odem &/odulator 5 "emodulator)

Modem is a device which converts di!ital si!nals intoanalo! for transmission over analo! transmission

facilities such as telephone lines. &t the receivin! end, a

modem performs the reverse function and convertsanalo! si!nal into di!ital form. /he process of convertin!

di!ital si!nal to analo! si!nal is called modulation. /heprocess of convertin! analo! si!nal to di!ital si!nal is

called demodulation. & modem can also amplif( a si!nalso that it can travel a lon! distance without attenuation.

Modem is available in two verities " $nternal or 10ternal.

#6 5 78

RA-8B, short form of Re!istered Aack - 8B, is an ei!ht

wired connector that is used to connect computers on a

local area network +&2, especiall( 1thernet. RA-8Bconnectors look similar to the RA- connector used for

connectin! telephone e4uipment, but the( are somewhat

wider.

Ethernet Card

&n 1thernet card is a kind of network adapter and is also

known as 2etwork $nterface Card +2$C. /hese adapters

support the 1thernet standard for hi!h-speed networkconnections via cables. &n 1thernet Card contains

connections for either coa0ial or twisted pair cables or

fibre optic cable

9u

$t is an electronic device that connects several nodes to form a network and redirects the received information to

the connected nodes in broadcast mode. & hub has ports into which the cables from individual computers 2$Cs

inserted. $t usuall( support 7, #, #8 RA " 87 connectors.

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http://en.wikipedia.org/wiki/Image:Network_card.jpg


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+witch

& switch is an intelli!ent hub that connects several nodes to form a network and redirects the received informa

onl( to the intended node+s.

#epeater

& repeater is an electronic device that receives a si!nal,

amplifies it and then retransmits it on the network so that

the si!nal can cover lon!er distances. &n electrical si!nal

in a cable !ets weaker with the distance it travels, due toener!( dissipated in conductor resistance and dielectric

losses.

#outer

& Router is a network device that works like a brid!e to establish connection between two networks but it can han

networks with different protocols.

:ateway

& !atewa( is a network device that establishes an intelli!ent connection between a local network and e0te

networks with completel( different structures i.e. it connects two dissimilar networks. $n simple terms, it is a noda network that serves as an entrance to another network &2s or W&2s and can handle different protocols.

Wi4i Card

Wi-?i cards are small and portable cards that allow (our desktop or laptop computer to connect to the intethrou!h a wireless network. Wi-?i transmission is throu!h the radio waves. /he antenna transmits the radio si!

and these si!nals are picked up b( Wi-?i receivers such as computers and cell phones e4uipped with Wi-?i ca

/hese devices have to be within the ran!e of a Wi-?i network to receive the si!nals. /he Wi-?i card then readssi!nals and produces a wireless internet connection. Once a connection is established between user and the netw

the user will be prompted with a lo!in screen and password if the connection bein! established is a secure connect

Wi-?i cards can be e0ternal or internal. $f a Wi-?i card is not installed in (our computer, (ou ma( purchase

a *< antenna attachment and have it e0ternall( connected to (our device. Man( newer computers, mobile devetc. are e4uipped with wireless networkin! capabilit( and do not re4uire a Wi-?i card. @owever, it is importan

understand that the Wi-?i connection onl( e0ists between the device and the router. Most routers are fur

connected to a cable modem, which provides internet access to all connected devices.

Network $rotocol

& protocol is the special set of rules that two or more machines on a network follow to communicate with each ot/he( are the standards that allow computers to communicate. *ome of the important protocols used are as follows

%C$ ; I$ &%ransmission Control $rotocol ; Internet $rotocol)

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http://en.wikipedia.org/wiki/Image:4_port_netgear_ethernet_hub.jpg


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%ransmission Control $rotocol &%C$)

/he /ransmission Control 6rotocol +/C6 breaks the data into packets that the network can handle efficientlmana!es the assemblin! of a messa!e or file into smaller packets that are transmitted over the $nternet. $t verifie

the packets when the( arrive at the destination computer and then reassembles them in proper order. Data can be

in the intermediate network. *o /C6 adds support to detect errors or lost data and to tri!!er retransmission untildata is correctl( and completel( received.

Internet $rotocol &I$)

/he $nternet 6rotocol +$6 handles the address part of each packet so that it reaches to the ri!ht destination. $t !distinct address +called $6 address to each data packet. 1ach !atewa( computer on the network checks this addres

see where to forward the messa!e. 1ven thou!h some packets from the same messa!e are routed differentl( t

others, the(5ll be reassembled at the destination They are together known as the TCP/P protocol!

4%$ &4ile %ransfer $rotocol)

?ile /ransfer protocol is used for cop(in! files from one computer to another.

9yper %e2t %ransfer $rotocol &9%%$)

@//6 is the protocol that is used for transferrin! h(perte0t +i.e. te0t, !raphic, ima!e, sound, video etc. between tw

computers and is particularl( used on the World Wide Web. $t is a /C6;$6 based communication protocol andprovides a standard for Web browsers and servers to communicate.

@//6 is based on Client;*erver principle. Communication between the host and the client occurs throu!h are4uest;response pair. & connection is established between two computers - out of which one is client +!enerall( th

browser that initiates the re4uest and the other is the server that responds to the re4uest. &lso @//6 identifies the

resource that the client has re4uested for and informs the server about the action to be taken. When the user clicks

the h(perte0t link, the client pro!ram on their computer uses @//6 to contact the server, identif( the resource andthe server to respond with an action. /he server accepts the re4uest and then uses @//6 to respond to perform the

action.

$$$ &$oint to $oint $rotocol)

666 +6oint-to-6oint 6rotocol is used for communication between two computers usin! a serial interface, mostl( a

personal computer connected b( phone line to a server. ?or e0ample, an $nternet *ervice 6rovider +$*6 ma( prov(ou with a 666 connection so that the $*65s server can respond to (our re4uests, pass them on to the $nternet, and

forward (our re4uested $nternet responses back to (ou. $t was basicall( desi!ned to help communication between

s(stems throu!h telephone lines as it supports transmission of network packets over a serial point to point link.

666 is sometimes considered a member of the /C6;$6 suite of protocols. 1ssentiall(, it encapsulates and packa!es

(our computer5s /C6;$6 packets into 666 frames and then forwards them to the server over serial transmission lin

such as telephone lines, $*D2 etc. 666 defines the format of frame to be e0chan!ed between devices on one ormultiple links and also defines the authenticit( of the two devices. $t supports various authentication schemes such

Password Authentication Protocol+6&6 and Challenge "andshake Authentication protocol+C@&6.

E,mail $rotocols

+imple /ail %ransfer protocol &+/%$)

*M/6 stands for Simple #ail Transfer Protocolthat allows transmission of email over the $nternet. Most email

software is desi!ned to use *M/6 for communication purposes when sendin! email. $t onl( works for out!oin!messa!es. *o when an email has to be sent, the address of their $nternet *ervice 6rovider5s *M/6 server has to be

!iven. /he actual mail transfer is done throu!h Messa!e /ransfer &!ents +M/&. *o the client computer must hav

client M/& and the server must have a server M/&. *M/6 actuall( defines the M/& client and the server on theinternet.

*M/6 has a major disadvanta!e that it is relativel( eas( to send a messa!e with a fake sender address. /his result

spread of man( email-based viruses


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Most servers these da(s actuall( us a sli!htl( updated version of the *M/6 protocol called$S#TP %$&tended Sim

#ail Transfer Protocol'!/his was created to allow transmission of multimedia throu!h email. When someone senpicture or music file throu!h their email pro!ram, 1*M/6 communication codes are used to identif( the kind of d

bein! transferred. Multipurpose $nternet Mail 10tension +M$M1 is a supplementar( protocol that allows non &*C

data to be sent throu!h *M/6.

$ost 3ffice $rotocol


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I$ phones , $6 phones appear much like an ordinar( telephone or cordless phone. /he( are directl( connected to t

router or the &2. /he( have all the hardware and software necessar( ri!ht onboard to handle the $6 call. $6 6honare sometimes called Eo$6 telephones, *$6 phones or *oft phones.

Computer,to,computer , $t is the most eas( and simplest wa( to use Eo$6. /he basic hardware re4uirements are

follows' Computer

$nternet

*peakers

Microphone/he onl( cost involved with computer - to- computer Eo$6 is the monthl( $*6 fee.

/oile %elecommunication %echnologies

Mobile is a device which is portable. Mobile communication is based on cellular networks. & cellular network is

nothin! but a radio network. $n this network, land is divided into areas called cells. 1ver( cell in the network has a

transmitter and a receiver known as cell site or base station. 1ach cell in the network uses different fre4uenc( for transmission of si!nals. When joined to!ether these cells provide radio covera!e over a lar!e !eo!raphical area. /

network of cells enables the mobile devices to communicate even if the( are movin! from one cell to another via

stations.

1: /oile +ystems/he = Mobile *(stem was introduced in late 93s and earl( 973s./he = mobile s(stem was based on the anacellular technolo!(. /he( onl( had voice facilit( available and were based on circuit-switched technolo!(. $n =

mobile s(stems voice was modulated to a fre4uenc( of about B3M@) and hi!her. /he( used radio towers for

transmission. /he major drawbacks of the = s(stem were its low capacit(, poor voice links and no securit(.


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/he mobile technolo!( usin! packet switched domain instead of circuit switched domain were termed as #.B= mo

s(stems. /he( used =6R* %,eneral Packet -adio Service'in addition to =*M. With #.B= services like MM*,sendin! pictures throu!h e-mail became possible. =6R* technolo!( was also a major step towards %= mobile s(s

=: /oile +ystem

/he %= technolo!( adds multimedia facilities to #= phones b( allowin! video, audio, and !raphics applications. W

the advent of %= technolo!( watchin! streamin! video or video telephon( became a realit(. /he idea behind %= i

have a sin!le network standard instead of the different t(pes adopted in the *, 1urope, and &sia. %= mobile s(stare also known as niversal Mobile /elecommunications *(stem +M/* or $M/-#333. /he( can sustain hi!her

rates and open the door to man( $nternet st(le applications. /he main characteristics of $M/-#333 %= s(stems are & sin!le famil( of compatible standards that can be used worldwide for all mobile applications.

*upport for both packet-switched and circuit-switched data transmission.

Data rates up to # Mbps +dependin! on mobilit(.

@i!h bandwidth efficienc(

7: /oile +ystem

8= networks will be based on packet switchin! onl(. $t will be able to support faster transmission. /he( are projec

to provide speeds up to 33 Mbps while movin! and =bps while stationar(. $t is a wireless access technolo!(. 8=can provide better-than-/E 4ualit( ima!es and video-links.

Network +ecurity Concepts

2etwork securit( deals with policies adopted b( network administrator to protect the network from unauthori)ed

access and misuse of network resources. $t also ensures that the authori)ed users have ade4uate access to all the

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%ro'an 9orse

& /rojan horse is a pro!ram that contains hidden malicious functions. /rojan @orses trick users into installin! themb( appearin! to be le!itimate pro!rams. Once installed on a s(stem, the( reveal their true nature and cause dama!

*ome /rojan horses will contact a central server and report back information such as passwords, user $Ds, and

captured ke(strokes. /rojans lack a replication routine and thus are not viruses b( definition.

+pam

/he term spam means endless repetition of worthless te0t. $n other words, unwanted messa!es or mails are known*pam. &t times internet is flooded with multiple copies of the same messa!e, it is nothin! but spam. Most spam is

commercial advertisin!. $n addition to wastin! people5s time, spam also eats up a lot of network bandwidth.

Cookies

When the user browses a website, the web server sends a te0t file to the web browser. /his small te0t file is a

cookie. =enerall( a cookie contains the name of the website from which it has come from and a uni4ue $D ta!.

*ome cookies last onl( until the browser is closed. /he( are not stored on (our hard drive. /he( are usuall( used ttrack the pa!es that (ou visit so that information can be customi)ed for (ou for that visit. On the other hand, some

cookies are stored on (our hard drive until (ou delete them or the( reach their e0pir( date. /hese ma(, for e0ampl

be used to remember (our preferences when (ou use the website.

4irewall

& firewall is hardware or software based network securit( s(stem. $t prevents unauthori)ed access +hackers, viruseworms etc. to or from a network. ?irewalls are used to prevent unauthori)ed internet users to access private netwo

connected to the $nternet. &ll data enterin! or leavin! the $ntranet pass throu!h the firewall, which e0amines each

packet and blocks those that do not meet the specified securit( criteria.

& firewall e0amines all traffic routed between the two networks to see if it meets certain criteria. $f it does, it is robetween the networks, otherwise it is stopped. & firewall filters both inbound and outbound traffic. & firewall ma(

allow all traffic throu!h unless it meets certain criteria, or it ma( den( all traffic unless it meets certain criteria.

Cyer Crime

C(bercrime is defined as a crime in which a computer and internet is used in an ille!itimate wa( to harm the user.

C(ber criminals ma( use computer technolo!( to access personal information, business trade secrets, or use theinternet for e0ploitive or malicious purposes. C(bercrimes can be a!ainst persons or a!ainst propert( or a!ainst th

!overnment.

%he list of Cyer Crimes includes

harassment b( computer +C(ber *talkin!, defamation

porno!raph(

ille!al downloads, pla!iarism

software pirac(;counterfeitin!, cop(ri!ht violation of software, counterfeit hardware, black market

sales of hardware and software, theft of e4uipment and new technolo!ies

fraud +credit card fraud, fraudulent use of &/M accounts, stock market transfers, telecommunications

fraud, theft of +electronic mone(

Cyer aw

C(ber law is an attempt to inte!rate the challen!es presented b( human activit( on the internet with le!al s(stem olaws applicable to the ph(sical world.

/here was no act in $ndia for !overnin! C(ber aws involvin! privac( issues, jurisdiction issues, intellectual prop

ri!hts issues and a number of other le!al 4uestions. With the tendenc( of misusin! of technolo!(, there has arisen

need of strict le!al laws to re!ulate the criminal activities in the c(ber world and to protect the true sense oftechnolo!(. G$2?ORM&/$O2 /1C@2OO=H &C/, #333G I$/&- #333J was enacted b( 6arliament of $ndia to

protect the field of e-commerce, e-!overnance, e-bankin! as well as penalties and punishments in the field of C(b

Crimes. /he above &ct was further amended in the form of $/ &mendment &ct, #337 I$/&&-#337J.

B


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$n the $/ &ct the word 5computer5 and 5computer s(stem5 have been so widel( defined and interpreted to mean an(electronic device with data processin! capabilit(, performin! computer functions like lo!ical, arithmetic and mem

functions with input, stora!e and output capabilities.

+ome of the C0E# 344ENCE+ -N"E# %9E I% AC%

/amperin! with computer source documents - *ection :B

@ackin! -*ection ::

6ublishin! of information which is obscene in electronic form -*ection :

Intellectual property rights &I$#) Issues

$ntellectual propert( ri!hts are the ri!hts !iven to an individual over the invention of their own. /he( usuall( !ivecreator an e0clusive ri!ht over the use of his;her creation for a certain period of time.

%here are only three ways to protect intellectual property

1. $atents

& 6atent is a term used for a specific product desi!ned b( an individual. /he desi!ner is !iven e0clusive ri!hts ov

the patent for a limited period of time. With help of the patent ri!ht, the owner can stop others from makin!, usin!

sellin! the product desi!n. /he owner can take a le!al action if someone uses the patent without his; her permissio$n order to obtain a patent, the followin! conditions should be met'

/he product should be new

$t should be capable of bein! made or used in some kind of industr(

$t should not be a scientific or mathematical discover(

$t should not be a dramatic, musical dramatic or artistic work

>. %rademarks

/rademark can be defined as a name or a different si!n or a device identif(in! a product or a service. /he product

the service is produced or provided b( a specific person or a compan(. & /rademark is also known as brand name

should be officiall( re!istered and le!all( restricted to use of the specific person or the compan(.

=. Copyrights

Cop(ri!ht is the term used for a written document. & le!al action can be taken, if cop(ri!hts are violated. /hefollowin! cate!or( of work can be considered for cop(ri!hts.

literar( works

musical works includin! an( accompan(in! words

dramatic works, includin! an( accompan(in! music

pantomimes and choreo!raphic works

pictorial, !raphic and sculptural works

motion pictures and other audio visual works

sound recordin!s

architectural works

computer pro!rams and websites

9acking

& computer enthusiast, who uses his computer pro!rammin! skills to intentionall( access a computer without

authori)ation is known as hackin!. /he computer enthusiast involved in this activit( is known as a hacker.

& hacker accesses the computer without the intention of destro(in! data or maliciousl( harmin! the computer.& cracker !ains unauthori)ed access to a computer with the intention of causin! dama!e.

Introduction to We +ervices

9%/ &9yperte2t /arkup anguage)

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@/M is lan!ua!e the helps in creatin! and desi!nin! web content. $t is a markup lan!ua!e. $t has a variet( of ta!

and attributes for definin! the la(out and structure of the web document. $t is desi!ned to displa( the data informatted manner. & @/M document has the e0tension .htm or .html."yperte&tis a te0t which is linked to anoth

document.

@/ &e@tensile /arkup anguage)

FM is a markup lan!ua!e like @/M. $t is desi!ned to carr( or store data. $n contrast to @/M, it is not desi!ne

to displa( data. nlike @/M, it does not have predefined ta!s. $t is possible to define new ta!s in FM. $t allow

the pro!rammer to use customi)ed ta!s. FM is case sensitive. FM is dei!ned to be self descriptive. FM is a Wrecommendation.

XML documents form a tree structure.

?or 10ample

KrootLKchildL

KsubchildL.....K;subchildL

K;childLK;rootL

Computer *cience

WWW &World Wide We)*

WWW can be defined as a h(perte0t information retrieval s(stem on the $nternet. $t is invented b( /im


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We rowser

Web browser is software pro!ram to navi!ate the web pa!es on the internet. & bowser interprets the codin! lan!ua

of the web pa!e and displa(s it in !raphic form. & web browser allows an(one to access the web without even

knowin! commands used in software lan!ua!es to desi!n a web pa!e. $nternet works on client -server model. & wbrowser is a client which re4uests the information from the web server. /he web server sends the information bac

the client. /he web address of the webpa!e written on the address bar tells the web browser which pa!e to access.

*ome of the web browsers are' 2etscape 2avi!ator, $nternet 10plorer, Mo)illa ?irefo0 etc.

-# &-niform resource locator)

Web address of the web pa!e written on the address bar of the browser is known as the uniform resource locator

+R. & R is a formatted te0t strin! used to identif( a network resource on the $nternet. 2etwork resources arfiles that can be plain Web pa!es, te0t documents, !raphics, downloadable files, services or pro!rams. 1ver( netw

resource on the web has a uni4ue R.

%he -# te2t string consists of three parts*

network protocol

host name or address

file or resource location

/he te0t strin! of a R has the followin! format'protocol';;server;path;resource

Network $rotocol

/he network protocol substrin! identifies the protocol to be used to access the network resource. /hese strin!s are

short names followed b( the three characters 5' ;;. *ome e0amples of protocols include http, !opher, ftp and mailt

-# 9ost;+erver

/he host name or address substrin! identifies the host;server that holds the resource. @osts names are sometimescalled domain names. ?or e0ample' www. *chool.com is a domain name.

@ost names are mapped into numeric $6 addresses. /he domain name www.school.com ma( have $6 address

9#.#.33..&n $6 address is a binar( number that uni4uel( identifies computers and other devices on a /C6;$6network.@ost names are mapped to $6 addresses b( a server known as a D2* server, or domain name server. D2* stands f

Domain Name Service!

-# #esource ocation

/he file or resource location substrin! contains a path to one specific network resource on the host;server. Resour

are normall( located in a host director( or folder. ?or e0ample'www.school.com;syllaus;preprimary;nursery.his the location of this web pa!e includin! two subdirectories and the file name. When the location element is omit

such as in http*;; www.school.com;the R conventionall( points to the root director( of the host and often a ho

pa!e.

We +erver

& Web server is a computer or a !roup of computers that stores web pa!es on the internet. $t works on client;serve

model. $t delivers the re4uested web pa!e to web browser. Web servers use special pro!rams such as &pache or $$deliver web pa!es over the http protocol.

1ach server has a uni4ue $6 address and domain name. $n order to access a webpa!e, the user writes the R of th

site on the address bar of the browser. /he machine on which the browser is runnin! sends a re4uest to the $6 addrof the machine runnin! the web server for that pa!e. Once the web server receives that re4uest, it sends the pa!e

content back to the $6 address of the computer askin! for it. /he web browser then translates that content into all o

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the te0t, pictures, links, videos, etc. & sin!le web server ma( support multiple websites or a sin!le website ma( be

hosted on several linked servers.

We hosting

Web hostin! is the process of uploadin!;savin! the web content on a web server to make it available on WWW. $ncase an individual or a compan( wants to make its website available on the internet, it should be hosted on a web

server.

We >.B

/he term web #.3 was !iven b( O5Reill( Media in #338. Web #.3 refers to new !eneration of d(namic and interac

websites. Web #.3 websites uses a new pro!rammin! lan!ua!e called &A&F +&s(nchronous Aava*cript and FM

&A&F helps a d(namic website connect to the web server and download small amount of data based on theinteraction with the user. $n this technolo!( onl( the part of the website which is updated is reloaded. /he entire p

does not !et reloaded each time. /his helps in makin! the website interactive.

Applications supported y we >.B are as followings*

blo!!in!

social bookmarkin!

R** +Reall( *imple *(ndication

wikis and other collaborative applications

interactive enc(clopedias and dictionaries &dvanced =amin!

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network 2014 cbse class 12

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