NETWORKS
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Transcript of NETWORKS
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