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Introduction to Information networksIntroduction to Information networks

Information networksare networks that transmit informationin versatile human and

technical networksto enhance knowledge, business or social aims. Often they useinformation technologyin contrast tobiological neural networksorsocial networks

research. They may use information portals or other types of collaborative networking for

sharing information.

Information networks refer to using the contemporary networking technologies such as

Internetand wireless communicationfor distributing and sharing information among

these different technical networks that any human networkcan benefit of. Essentially,

information network is linked to exchanging information between interest groups withinand between human institutionssuch as companies, universities, research organizations,

and communities.

computer network, often simply referred to as a network, is a collection of computers

and devices connected by communications channels that facilitates communicationsamong users and allows users to share resources with other users. !etworks may be

classified according to a wide variety of characteristics. This article provides a general

overview of types and categories and also presents the basic components of a network.

Purpose

"omputer networks can be used for several purposes#

Facilitating communications.$sing a network, people can communicate

efficiently and easily via e%mail, instant messaging, chat rooms, telephone, video

telephone calls, and video conferencing.

Sharing hardware.In a networked environment, each computer on a network can

access and use hardware on the network. &uppose several personal computers ona network each re'uire the use of a laser printer. If the personal computers and a

laser printer are connected to a network, each user can then access the laser

printer on the network, as they need it.

Sharing files, data, and information.In a network environment, any authorized

user can access data and information stored on other computers on the network.

The capability of providing access to data and information on shared storage

devices is an important feature of many networks. Sharing software.$sers connected to a network can access applicationprograms

on the network.

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NetworksNetworksConnecting two or More Computers makes a Computer Network to ShareConnecting two or More Computers makes a Computer Network to Share

Resources.Resources.In IInformation TTechnology, a NetworkNetworkis a series of points ora series of points ornodenodes interconnecteds interconnected

by communication pathsby communication paths. !etworks can interconnect with other networks and containsubnetworks. !etworks classified according to Topologyand rea or scope of use.

TopologyTopology topology )from *reek toposmeaning place+ is a description of any kind of locality interms of its layout. In communication networks, a topology is a usually schematic

description of the arrangement of a networkthe arrangement of a network, including its nodes and connecting lines.

There are two ways of defining network geometry# the Physical topologyPhysical topologyand the

ogical !or signal" topologyogical !or signal" topology.

The physical topologyof a network is the actual geometric layout of workstations. Thereare several common physical topologies, as described below and as shown in the

illustration. )These what are used in !s+.

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(% In the bus networktopology# e$ery workstationis connected to a main cable calledthe bus.Therefore, in effect, each workstation is directly connected to every other

workstation in the network.

-% In the star networktopology# there is a central computer or ser$er to which all the

workstations are directly connected. Every workstation is indirectly connected to everyother through the central computer.

% In the ring networktopology# the workstations are connected in a closed loop

configuration. d/acent pairs of workstations are directly connected. Other pairs of

workstations are indirectly connected, the data passing through one or more intermediate

nodes.

0% variation of the ring network topology is known as the Token Ring. In this scheme#

the signal tra$els in only one direction or senses around the ring# carried by a so%

called token from node to node.

1% Themesh networktopology employs either of two schemes, called full meshand

partial mesh. In the full mesh topology# each workstation is connected directly to

each of the others. In the partial mesh topology# some workstations are connected to

all the others# and some are connected only to those other nodes with which they

e&change the most data.

2% Thetree networktopology uses two or more star networks connected together .The central computers of the star networks are connected to a main bus. Thus, a tree

network is a bus network of star networks.

ogical !or signal" topologyrefers to the nature of the paths the signals follow fromnode to node. In many instances, the logical topology is the same as the physicaltopology. 3ut this is not always the case. 4or example, some networks are physically laid

out in a star configuration, but they operate logically as bus or ring networks.

Important note' !Readthe (d$antagesand disad$antagesof each Topology

HERE)+

*ui+ !,"' Test yourselfHere)

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Network Types !(rea"'

,%(N -%M(N %/(N 0%Internet 1%Intranet 2%3&tranet

,%,% ocalocal ((rearea NNetworketwork !!(N(N""## local area network )(N+ is a group of computers and associated de$ices that sharea common communications line or wireless link and typically share the resources of

a single processor or ser$er within a small geographic area )for example, within an

office building+. $sually, the server has applications and data storage that are shared in

common by multiple computer users. local area network may serve as few as two or

three users )for example, in a home network+ or as many as thousands of users )forexample, in an 455I network+.

6a/or local area network technologies are#

EthernetToken 7ing

455I

3thernetis by far the most commonly used (N technology. number of

corporations use the Token 7ing technology. 455I is sometimes used as abackbone

! interconnecting Ethernet or Token 7ing !s. nother ! technology,

7"!ET, once the most commonly installed ! technology, is still used in theindustrial automation industry.

Typically, a suite of application programs can be kept on the ! server. $sers who needan application fre'uently can download it once and then run it from their local hard disk.$sers can order printing and other services as needed through applications run on the

! server. user can share files with others at the ! server8 read and write access is

maintained by a ! administrator. ! server may also be used as a 9eb serverif

safeguards are taken to secure internal applications and data from outside access.

In some situations, a wireless !may be preferable to a wired ! because it is

cheaper to install and maintain.

--%%MMetropolitanetropolitan ((rearea NNetworketwork !!M(NM(N"'"'

metropolitan area network )M(N+ is a network that interconnects users with computerresources in a geographic area or region larger than that covered by even a large local

area network )!+ but smaller than the area covered by a wide area network )9!+.

The term is applied to the interconnection of networks in a city into a single larger

network)which may then also offer efficient connection to a wide area network+. It isalso used to mean the interconnection of several local area networks by bridging them

withbackbonelines. The latter usage is also sometimes referred to as a campus network.

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Examples of metropolitan area networks of various sizes can be found in the metropolitan

areas of ondon, England8 odz, :oland8 and *eneva, &witzerland. arge universities

also sometimes use the term to describe their networks. recent trend is the installationof wireless 6!s.

%%//ideide ((rearea NNetworketwork !!/(N/(N"'"'

wide area network )9!+ is a geographically dispersed telecommunicationsnetwork;Network that connecting Networks between countries of large cities .

00%%InternetInternet' The Internet, sometimes called simply

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$sing the 9eb, you have access to millions of pages of information. 9eb browsing is

done with a 9ebbrowser, the most popular of which are 6icrosoft Internet Explorer and

!etscape !avigator. The appearance of a particular 9eb site may vary slightly dependingon the browser you use. lso, later versions of a particular browser are able to render

more s information or

operations with suppliers, vendors, partners, customers, or other businesses. (n e&tranetcan be $iewed as part of a company4s intranetthat is e&tended to users outside the

company. It has also been described as a

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-+ On the Internet or other wide area network, a backbone is a set of paths that local or

regional networks connect to for long%distance interconnection. The connection points are

known as network nodesor telecommunication data switching exchanges )5&Es+.

6ridge'

In telecommunication networks, a bridge is a product that connects a local area

network !(N" to another local area network that uses the same protocol!for

e&ample# 3thernetor Token Ring". @ou can envision a bridge as being a device that

decides whether a message from you to someone else is going to the local area network inyour building or to someone on the local area network in the building across the street.

bridge examines each message on a !,

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pairs of coaxial tubes can be placed in a single outer sheathing and, with repeaters, can

carry information for a great distance.

"oaxial cable was invented in (=-= and first used commercially in (=0(. TCTestablished its first cross%continental coaxial transmission system in (=0D. 5epending on

the carrier technology used and other factors, twisted paircopper wire andoptical fiberare alternatives to coaxial cable.

8ptical 9iber Cable'

Twisted Pairs Cable !7TP and STP":

Important Note' ReadallCables DetailsHere!

*ui+ !-"' Test yourselfHere)

3thernet Card'

3thernet is the most widely%installed local area

network ! (N" technology. &pecified in a standard,

IEEED-., Ethernet was originally developed byFerox from an earlier specification calledAlohanet

)for the :alo lto 7esearch "enter loha network+and then developed further by Ferox, 5E", and Intel.n Ethernet ! typically uses coaxial cableor special grades of twisted pairwires.

Ethernet is also used in wireless !s. The most commonly installed Ethernet systems

are called (D3&E%Tand provide transmission speeds up to (D 6bps. 5evices are

connected to the cable and compete for access using a "arrier &ense 6ultiple ccess with"ollision 5etection )"&6?"5+ protocol.

4ast Ethernet or (DD3&E%T provides transmission speeds up to (DD megabits per second

and is typically used for ! backbone systems, supporting workstations with (D3&E%T cards. *igabit Ethernet provides an even higher level of backbone support at (DDD

megabits per second )( gigabit or ( billion bits per second+. (D%*igabit Ethernet providesup to (D billion bits per second.

Ethernet was named by 7obert 6etcalfe, one of its developers, for the passive substancecalled

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Ethernet was so% named to describe the way that cabling, also a passive medium, could

similarly carry data everywhere throughout the network.

/ireless (N'

wireless ! )or 9!, for wireless local area network, sometimes referred to as9!, for local area wireless network+ is one in which a mobile user can connect to alocal area network )!+ through a wireless)radio+ connection.

Gigh%bandwidth allocation for wireless will make possible a relatively low%cost wiring of

classrooms in the $nited &tates. similar fre'uency allocation has been made in Europe.Gospitals and businesses are also expected to install wireless ! systems where

existing !s are not already in place.

;ateway'

( gateway is a networkpoint that acts as anentrance to another network that uses different

protocols. On the Internet, a nodeor stopping point can be either a gateway node or a

host)end%point+ node. 3oth the computers of Internet users and the computers that serve

pages to users are host nodes. The computers that control traffic within your company>s

network or at your local Internet service provider )I&:+ are gateway nodes.

In the network for an enterprise, a computer serveracting as a gateway node is often also

acting as aproxy serverand afirewallserver. gateway is often associated with both a

router, which knows where to direct a givenpacketof data that arrives at the gateway,

and a switch, which furnishes the actual path in and out of the gateway for a given

packet.

576'

7sed as a Repeater# to imitate a Star

network using a 6us network.

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Router'

routeris a device that forwards data packets

between telecommunications networks, creatingan overlay internet.

9hen data comes in on one of the lines, the router

reads the address information in the packet to

determine its ultimate destination. Then, using

information in its routing tableor routing policy,it directs the packet to the next network on its /ourney or drops the packet. data

packet is typically forwarded from one router to another through networks that

constitute the internetwork until it gets to its destination node.

Modem'

3nables to send and recei$e data through Telephone

lines.

"omputerHs 5igital data are converted to nalog signals tobe transmitted through Telephone lines, then again turned to

digital when reached to other side computer.

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>,,>,,,>,>>>,> Network Network

CardCard Communication ineCommunication ine Card Card

:arallel Transmission &erial Transmission :arallel Transmission:arallel Transmission &erial Transmission :arallel Transmission

Sender ComputerSender Computer Receiver ComputerReceiver Computer

The Process of data TransmissionThe Process of data Transmission

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

??? !Calculation 3&amples about Networks Transmitting speed" ???

a-Internet $pload or 5ownloadSpeedis normally measured by @b)Kilo Bit+or @6)Kilo Byte+ :erSecond, 4or Example when transmitting date via anetwork line with a speed of -12Jb?s , and another line with a speed of

12J3?s, Then the &econd line is considered 4aster than the 4irst line because #

-12K(D-0 L -2-(00 3it?s

&ince the 3yteL 3its, Then# 12K(D-0KL 01B1- 3it?s, which is Faster...

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b-To find approximately, the number of text Charactersto be transmitted via a

network line )for instance 12J3?s+ 5uring a period of time )Two Gours for

example+, 9e do the following#

)12K(D-0K(-DK2D+ L 0(-,B2,DD "haracters to be transmitted

9hile, if we considered the speed of -12Jb?s, and assuming a "haracter

L(3yte L A3its , Then we get#

)-12K(D-0K(-DK2D+? L -1,=-=,2DD "haracters.

c% To 4ind approximately the !umber of 3its to be transmitted during a period of time ,

)for instance, -J3?s and -Jb?s during 6inutes+, then all what we have to do is#

-K(D-0KK2DK L 0B,(1,=-D 3its

9hile for the second case#

-K(D-0K2DK L 1,=,-0D 3its...

ote! ClickHereto "et a brief steps in connectin" #$Cs%

Post TestPost Test''&nswer the 'uestions in&nswer the 'uestions inHereHere)

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