NETWORKSNETWORKS

LANs & WANs RequirementsLANs & WANs Requirements

andand

Advantages & Disadvantages of the InternetAdvantages & Disadvantages of the Internet

Learning ObjectivesLearning Objectives

Discuss the hardware and software requirements for LANs and WANs to function.

Explain the relationship between baseband and broadband.

Identify the advantages and disadvantages of using the Internet.

Structure DiagramStructure Diagram

INPUT DEVICES

MAIN MEMORY

PROCESSOR OUTPUT DEVICES

AUXILIARY STORAGE

ROM

COMMUNICATIONS

CommunicationsCommunications

Sending and receiving data to and from Sending and receiving data to and from other computers.other computers.

Communications softwareCommunications software

Necessary to allow computers to Necessary to allow computers to communicate.communicate.

Network Components for Network Components for a LANa LAN

Network Cards & CablesNetwork Cards & Cables

NNetwork etwork IInterface nterface CCards ards ((NICNICs)s) Allows communication between Allows communication between

computers in a LAN.computers in a LAN.

Cable Cable Connects the computers Connects the computers

together.together.

RepeaterRepeaterAmplifies the signals between two LANs that are Amplifies the signals between two LANs that are too far apart.too far apart.Is not intelligent and simply amplifies all signals Is not intelligent and simply amplifies all signals whether they are intended for computers on the whether they are intended for computers on the other segment or not.other segment or not.

Repeater

LAN 1

LAN 2

HubsHubs

Hub

HubsHubs

Is not intelligent as all signals received by Is not intelligent as all signals received by a hub are retransmitted down every other a hub are retransmitted down every other cable connected to it enabling a physical cable connected to it enabling a physical star network.star network. Multi-port repeaters.Multi-port repeaters.

BridgesBridgesAmplifies the signals between two LANs that are Amplifies the signals between two LANs that are too far apart.too far apart.Is intelligent as it only amplifies signals which are Is intelligent as it only amplifies signals which are intended for computers on another LAN.intended for computers on another LAN. Intelligent RepeaterIntelligent Repeater

Bridge

LAN 1

LAN 2

Backbone

ServerStations

Switch

ServerStations

Switch

ServerStations

Switch

ServerStations

Switch

Note: Networks with combined typologies (like the one below) are called Tree

or Hybrid networks.

SwitchSwitch

A switch is intelligent as signals received by a A switch is intelligent as signals received by a switch are only sent to the intended recipient switch are only sent to the intended recipient computer computer (not down all cables)(not down all cables)..

Intelligent hubIntelligent hub Like a bridge but can link many LANs.Like a bridge but can link many LANs.

It allows many terminals all to use the same It allows many terminals all to use the same communications line communications line (backbone – fast medium e.g. optical (backbone – fast medium e.g. optical fibre)fibre) between network segments at different times. between network segments at different times. If all stations want to access the main network, the switch has If all stations want to access the main network, the switch has

no affect on the speed of this link and it may be necessary to no affect on the speed of this link and it may be necessary to upgrade the link to the main network.upgrade the link to the main network.

WANs (WANs (WWide ide AArea rea NNetworks)etworks)Networks with computers that cover a large Networks with computers that cover a large geographical area. geographical area. e.g. large companies with offices or factories in widely e.g. large companies with offices or factories in widely

separated areas, like Microsoft, IBM, Ford, AT&T, etc. separated areas, like Microsoft, IBM, Ford, AT&T, etc. The internet is also an example of a WAN.The internet is also an example of a WAN. Will usually use some form of long range Will usually use some form of long range

telecommunication e.g. telephone wires, satellite links telecommunication e.g. telephone wires, satellite links etc…etc…

Network Components for Network Components for a WANa WAN

RoutersRouters

LAN Router Public network

Router LAN

RoutersRouters

Connect LANs & WANs together.Connect LANs & WANs together. e.g. connect a LAN to the internet using e.g. connect a LAN to the internet using

one IP address.one IP address.Directs signals down different routes Directs signals down different routes according to their desired destinations.according to their desired destinations.

Analogue DataAnalogue DataAnalogue devices such as:

Clocks Thermometers Phones Speakers

Represent variables by an analogous quantity or variations variations (modulations)(modulations) :

Time is represented by the angle of the hands.

Temperature is represented by the height of a column.

Sound waves on a normal phone line or from speakers.

Digital DataDigital Data

Computers work with data in a digital form. Streams of 0's and 1's

Need for conversionNeed for conversion

If computers are to receive or send analogue data (sensors, speakers, phone lines, etc…). There must be conversion between analogue

and the digital data computers use. Devices which do this are called:

ADCs (Analogue to Digital Converters)

ModemModem

Modem:Modem: A hardware device that allows computers or A hardware device that allows computers or

other digital devices e.g. faxes to other digital devices e.g. faxes to communicate using telephone lines.communicate using telephone lines.

Converts analogue phone signals to digital data Converts analogue phone signals to digital data which the computer can understand.which the computer can understand.

Converts digital data to analogue phone signals so Converts digital data to analogue phone signals so they can be transmitted through the phone linethey can be transmitted through the phone line

Baseband

Vs

Broadband

Coaxial cableCoaxial cable

Baseband coaxial:Baseband coaxial: Single copper braid shield.Single copper braid shield.

Broadband coaxial:Broadband coaxial: Two shields (1 - aluminium & 1 - copper).Two shields (1 - aluminium & 1 - copper).

Central conductorPlastic insulators

Copper screen conductor

A central conductor enclosed in a plastic sheath A central conductor enclosed in a plastic sheath surrounded by a copper sheath which is surrounded by a copper sheath which is surrounded by a plastic coating.surrounded by a plastic coating.

Baseband

Data carried as digital signals.

Uses the entire bandwidth (as only one frequency or channel is used) of the media.

Frequency-division / multiplexing is not possible.

Bi-directional.

Ethernet.

Broadband

Data carried as analogue signals.Each transmission is assigned to a portion of the bandwidth.Multiple transmissions are possible at the same time.Can simultaneously transport multiple signals and traffic types.Uni-directional.To send and receive needs two pathways by assigning a frequency for sending and a different frequency for receiving.Frequency-division / multiplexing is possible. Can use coaxial cable, optical fibre, twisted pair, or wireless broadband (wireless broadband includes Mobile broadband).

Baseband

Advantages: Simplicity Low cost Ease of installation

and maintenance. High rates.

Disadvantages: Limited distances.

Advantages: Greater distances. Greater bandwidth.

Disadvantages: Difficult to install and

maintain. High cost, requires

modems. Lack of well-developed

standards.

Broadband

Extra Research

http://www.webclasses.net/demo/intro/5.2/sp/units/unit4_sec3.html

http://ecomputernotes.com/computernetworkingnotes/communication-networks/broadband-versus-baseband

http://www.omnisecu.com/basic-networking/difference-between-baseband-and-broadband.php

Firewalls & Proxy servers

Firewall Software to protect LAN from unwanted access.

Proxy server to allow one Internet connection for whole network.

This allows more control over the internet access of the This allows more control over the internet access of the workstations on the LAN as it acts as an intermediary server.workstations on the LAN as it acts as an intermediary server.

InternetInternet

The Internet is worldwide and intended to The Internet is worldwide and intended to be accessed by anybody.be accessed by anybody.

A global network connecting millions of A global network connecting millions of computers. computers.

More than 100 countries are linked into More than 100 countries are linked into exchanges of data, news and opinions. exchanges of data, news and opinions.

Advantages

Convenience:Convenience: accessible at home, work, or through a wireless accessible at home, work, or through a wireless

devicedevice

Easy to contact other people no matter where Easy to contact other people no matter where they are. they are. Access to other cultures Access to other cultures Access to a vast amount of information Access to a vast amount of information Can be used Night or Day - it never stops Can be used Night or Day - it never stops Can be used to learn (or teach) Can be used to learn (or teach) Makes it possible to Telework Makes it possible to Telework Possible to buy and sell things online Possible to buy and sell things online

Advantages

Can present their work more neatly

Pupils can share ideas

Less waste of paper

Disadvantages

Must have a home computerMust have a home computer

Transmission of virusesTransmission of viruses

Must have Internet / ModemMust have Internet / Modem

Must remember passwords / usernamesMust remember passwords / usernames

Pupils can copy off othersPupils can copy off others

DisadvantagesDisadvantages

Undesirable sites may be accessedUndesirable sites may be accessedHave to pay for internet accessHave to pay for internet accessMay receive unsolicited e-mails from May receive unsolicited e-mails from undesirable charactersundesirable charactersHealth reasonsHealth reasonsDemand on equipmentDemand on equipmentCan waste time exploring unreliable sitesCan waste time exploring unreliable sitesCan get distracted playing gamesCan get distracted playing games

PlenaryPlenary

What are the hardware and software requirements for LANs and WANs?

LANs & WANSCommunications Software

Cable

Server

Network Card WANs

Communications Software

Server

Modem

Plenary

Explain what is meant by baseband and broadband.

Baseband

Data carried as digital signals.

Uses the entire bandwidth (as only one frequency or channel is used) of the media.

Frequency-division / multiplexing is not possible.

Bi-directional.

Ethernet.

Broadband

Data carried as analogue signals.Each transmission is assigned to a portion of the bandwidth.Multiple transmissions are possible at the same time.Can simultaneously transport multiple signals and traffic types.Uni-directional.To send and receive needs two pathways by assigning a frequency for sending and a different frequency for receiving.Frequency-division / multiplexing is possible. Can use coaxial cable, optical fibre, twisted pair, or wireless broadband (wireless broadband includes Mobile broadband).

PlenaryPlenary

What are the advantages and disadvantages of using the Internet?

Advantages

Allows communication.Allows communication.

Pupils can share ideas.Pupils can share ideas.

Large amounts of educational material.Large amounts of educational material.

Allows students to access information to Allows students to access information to help with studies and to enjoy their help with studies and to enjoy their learning.learning.

Allows student to learn at own speed / at Allows student to learn at own speed / at own times.own times.

Disadvantages

Many sites do not give accurate information.Many sites do not give accurate information.

Many sites give access to inappropriate material Many sites give access to inappropriate material (downloading music / ordering drugs / watching (downloading music / ordering drugs / watching pornography).pornography).

Health and Safety problems.Health and Safety problems.

Sites available to buy coursework / helps to Sites available to buy coursework / helps to cheat in examinations.cheat in examinations.

May allow hacker into your system / viruses May allow hacker into your system / viruses prevalent.prevalent.

DisadvantagesDisadvantages

Undesirable sites may be accessedUndesirable sites may be accessedHave to pay for internet accessHave to pay for internet accessMay receive unsolicited e-mails from May receive unsolicited e-mails from undesirable charactersundesirable charactersHealth reasonsHealth reasonsDemand on equipmentDemand on equipmentCan waste time exploring unreliable sitesCan waste time exploring unreliable sitesCan get distracted playing gamesCan get distracted playing games