Standard Grade Standard Grade ComputingComputing

Communications and Communications and NetworksNetworks

What is a Network?What is a Network?

A series of computers linked A series of computers linked together so can send and receive together so can send and receive data. data.

They are divided into two types:They are divided into two types: Local Area Local Area Network (LAN)Network (LAN)

Wide Area Wide Area Network (WAN)Network (WAN)

Local Area NetworksLocal Area Networks

Local Area NetworksLocal Area Networks (LANs) operate (LANs) operate in one area, such as an office block, a in one area, such as an office block, a factory a school a bank or even a factory a school a bank or even a home home

The computers are joined together The computers are joined together using cables or wireless transmitters using cables or wireless transmitters

Advantages of LANsAdvantages of LANs

users can users can share peripheralsshare peripherals such as such as hard drives, printers, and web hard drives, printers, and web cameras cameras

users can users can share data filesshare data files such as such as database files, standard letters and database files, standard letters and multimedia presentations multimedia presentations

they make it easy to they make it easy to communicatecommunicate by sending e-mailsby sending e-mails

Copper CablingCopper Cabling

Coaxial cablingCoaxial cabling The central cable The central cable

that transmits the that transmits the data is surrounded data is surrounded by a shield of copper by a shield of copper braiding. This braiding. This protects it from protects it from interference and so interference and so is found in in places is found in in places such as factories such as factories where there could be where there could be a lot of interferencea lot of interference

Copper CablingCopper Cabling

Twisted-pair cablingTwisted-pair cabling This is a simple This is a simple

type of cabling type of cabling made up of two made up of two copper cables. It is copper cables. It is relatively cheap relatively cheap and can support and can support quite high quite high transmission transmission speeds, for example speeds, for example over 100 Mbits per over 100 Mbits per secondsecond

Fibre-optic CablesFibre-optic Cables

Fibre-optic cableFibre-optic cable is made up is made up of fine strands of glass that of fine strands of glass that carry pulses of lightcarry pulses of light

These pulses of light These pulses of light represent data being represent data being transmittedtransmitted

More difficult to break into More difficult to break into the cable and is more secure the cable and is more secure

Does not suffer from electro-Does not suffer from electro-magnetic interference magnetic interference

Transmits data at high speedTransmits data at high speed

Costs more to buy and install Costs more to buy and install than other types of cablingthan other types of cabling

Wireless NetworkingWireless Networking

Wireless networking transmits data Wireless networking transmits data through the air using through the air using radio wavesradio waves and and microwavemicrowave frequency radiation frequency radiation

a wireless network is relatively easy a wireless network is relatively easy to install, all you need is a to install, all you need is a transmitter/receiver and a wireless transmitter/receiver and a wireless Network Interface Card on each Network Interface Card on each computer on the network computer on the network

there is no need for any wiring there is no need for any wiring transmission speeds are very fasttransmission speeds are very fast

security is a problem, wireless security is a problem, wireless networks are easy to hack intonetworks are easy to hack into

Wireless ProtocolsWireless Protocols

Infrared Infrared communicationcommunication Like the TV controlsLike the TV controls

BluetoothBluetooth Range of about 10 Range of about 10

metresmetres WIFIWIFI ((Wireless Fidelity Wireless Fidelity

Alliance)Alliance) Range of about 12-Range of about 12-

50 metres50 metres

Network Interface CardNetwork Interface Card A NIC takes the data sent by your A NIC takes the data sent by your

computer on to the network, computer on to the network, stores it in its own memory stores it in its own memory locations and then adapts it to locations and then adapts it to make sure that it follows the make sure that it follows the communication rules that govern communication rules that govern the networkthe network

It takes data coming in from the It takes data coming in from the network to your computer and network to your computer and passes it on to the processorpasses it on to the processor

Every device that is connected to Every device that is connected to the LAN will need a NIC, e.g.. the LAN will need a NIC, e.g.. computer, printer and scanner computer, printer and scanner

Clients and ServersClients and Servers A A clientclient is a workstation on is a workstation on

the networkthe network A A serverserver is a computer that is a computer that

has a fast processor and has a fast processor and lots of memory and is used lots of memory and is used to to hold all the data files or the hold all the data files or the

applications software applications software organise the clients’ access organise the clients’ access

to the internetto the internet control the resources the control the resources the

client workstations can use. client workstations can use. For example printing, For example printing, internet access etcinternet access etc

Wide Area NetworksWide Area Networks

Wide Area NetworksWide Area Networks (WANs) connect (WANs) connect computers across large distancescomputers across large distances

WANs stretch across towns, link up WANs stretch across towns, link up cities and countries using cities and countries using telecommunications links telecommunications links

Wide Area NetworksWide Area Networks

people can communicate instantly worldwide people can communicate instantly worldwide they can be used tothey can be used to

send e-mail send e-mail send data files send data files carry out financial transactions carry out financial transactions work from home and still be in contact with the work from home and still be in contact with the

central office central office access information access information carry out research carry out research

WANs are central to the success of large WANs are central to the success of large businessesbusinesses

Wide Area NetworksWide Area Networks

Telecommunications linksTelecommunications links The communication of information over The communication of information over

a distance using:a distance using: Microwave transmissionMicrowave transmission Satellite linksSatellite links Optical FibreOptical Fibre

Multi-access ComputersMulti-access Computers

These are powerful computer systems These are powerful computer systems that enable many users tothat enable many users toaccess the system at the same time access the system at the same time share the processing power of the share the processing power of the system system share the available memory share the available memory share the data on the backing storageshare the data on the backing storage

Multi-access ComputersMulti-access Computers

Multi-access computers have many Multi-access computers have many terminalsterminals attached to them attached to them

These terminals are made up of keyboards These terminals are made up of keyboards and monitors that people use to and monitors that people use to interact with the main processor interact with the main processor load data to and from backing storage load data to and from backing storage display data held on the systemdisplay data held on the system

The key point about these terminals is that The key point about these terminals is that they have little or they have little or no local processing or no local processing or memorymemory

How does multi-access How does multi-access work?work?

It gives each terminal a It gives each terminal a sliceslice of the of the processor’s time. It goes round the users processor’s time. It goes round the users very quickly, so quickly that they are not very quickly, so quickly that they are not aware that they are sharing the system with aware that they are sharing the system with lots of other people lots of other people

Large organisations such as banks, Large organisations such as banks, insurance companies and mail-order insurance companies and mail-order companies as well as colleges and companies as well as colleges and universities use them to store and process universities use them to store and process their datatheir data

Security on NetworksSecurity on Networks

All networks need to have security All networks need to have security measures in placemeasures in place

If they do not then the network can If they do not then the network can be hacked into, data deleted, copied be hacked into, data deleted, copied or changedor changed

Physical Security MeasuresPhysical Security Measures

Physical security measures can prevent Physical security measures can prevent unauthorisedunauthorised people accessing the people accessing the networknetwork

Network computers with a physical lock Network computers with a physical lock Security locks on the computer roomsSecurity locks on the computer roomsComputers without floppy or CD drivesComputers without floppy or CD drives

Software Security MeasuresSoftware Security Measures

Authorised users are issued with Authorised users are issued with IDsIDs and and passwordspasswords to gain entry to the network to gain entry to the network

When users log on, the computer system When users log on, the computer system checks their IDs and passwords with those checks their IDs and passwords with those that it keeps on filethat it keeps on file

Some systems use Some systems use biometricbiometric systems to ID systems to ID authorised users. They store data about authorised users. They store data about fingerprints, voices or eyes fingerprints, voices or eyes

EncryptionEncryption encodes the data held on the encodes the data held on the system. This means that if the network is system. This means that if the network is hacked into then the data is meaningless to hacked into then the data is meaningless to the hackerthe hacker

Text MessagingText Messaging

Instant messagingInstant messaging allows allows you to send text you to send text messages to people on messages to people on their PCstheir PCs

Short text messagesShort text messages can can be sent to and from be sent to and from pagers, mobile phones, pagers, mobile phones, and palmtop computersand palmtop computers

Electronic-mail (e-mail)Electronic-mail (e-mail)

E-mails can be sent anywhere in the worldE-mails can be sent anywhere in the world Mail delivery is very Mail delivery is very fastfast It It costscosts a lot a lot lessless than surface mail than surface mail Web-based e-mail allows you to check your Web-based e-mail allows you to check your

inbox anywhere there is an internet connectioninbox anywhere there is an internet connection Multiple copiesMultiple copies of a message can be sent of a message can be sent

easilyeasily E-mail is E-mail is securesecure as an ID and password is as an ID and password is

needed to access itneeded to access it

Electronic-mail (e-mail)Electronic-mail (e-mail)

E-mail problemsE-mail problems

VirusesViruses can be hidden in e-mail can be hidden in e-mail attachmentsattachments

Lots of Lots of spamspam arrives by e-mail. Spam arrives by e-mail. Spam is unwanted adverts, special offers is unwanted adverts, special offers and general and general junk mailjunk mail

NetiquetteNetiquette

NetiquetteNetiquette is a set of rules that is a set of rules that govern the way people behave when govern the way people behave when using email, or a networkusing email, or a network

NetiquetteNetiquette

DON’T TYPE IN CAPS!DON’T TYPE IN CAPS! Don’t leave the Subject Field blankDon’t leave the Subject Field blank Do not start Do not start flame warsflame wars Do not use Do not use bad languagebad language, always be , always be

polite polite Use proper English in e-mails.Use proper English in e-mails. Do not post unwanted mail or use e-Do not post unwanted mail or use e-

mail to mail to spamspam

Email TaskEmail Task

Set your groupwise passwordSet your groupwise password Send an email to someone in the class Send an email to someone in the class

saying hello and giving some information saying hello and giving some information about what you did at the weekend.about what you did at the weekend.

Read any emails you receive.Read any emails you receive. Forward one of your messages to someone Forward one of your messages to someone

else in the class.else in the class. Customise the party invitation and save. Customise the party invitation and save. Send your invitation as an attachment to Send your invitation as an attachment to

five people in the class using BCCfive people in the class using BCC

InternetInternet

A Wide Area Network across the A Wide Area Network across the worldworld

The network of networksThe network of networks Lots of smaller networks joined togetherLots of smaller networks joined together

Accessing the InternetAccessing the Internet

To access the internet an internet-ready To access the internet an internet-ready computer system is required as followscomputer system is required as follows Desktop, laptop and palmtop computers Desktop, laptop and palmtop computers

are suitableare suitable A A modemmodem Telecommunications connection either Telecommunications connection either

dialupdialup or or broadbandbroadband A A browserbrowser An An internet service providerinternet service provider

ModemModem

It is a device that changes your It is a device that changes your computer’s signals into a form that computer’s signals into a form that can be sent down the phone systemcan be sent down the phone system

Dialup ConnectionDialup Connection

It uses a modem and an ordinary It uses a modem and an ordinary phone line to dial up the number of phone line to dial up the number of your ISP that connects you to the your ISP that connects you to the internetinternet

Data is transmitted at a speed of 56 Data is transmitted at a speed of 56 Kilobits per secondKilobits per second

Broadband ConnectionBroadband Connection

A broadband connection is a high-speed A broadband connection is a high-speed telecommunications linktelecommunications link

BT digital subscriber line (ADSL) gives BT digital subscriber line (ADSL) gives speeds of maximum 512 Kbps download speeds of maximum 512 Kbps download and 128 Kbps uploadand 128 Kbps upload

Cable modems can reach speeds up to 10 Cable modems can reach speeds up to 10 Megabits per second Megabits per second

Actual speeds are slower because the Actual speeds are slower because the cable bandwidth often has to be shared cable bandwidth often has to be shared with other userswith other users

BrowserBrowser

A browser is the software that fetches and A browser is the software that fetches and displays web pages e.g. displays web pages e.g. Microsoft ExplorerMicrosoft Explorer

Type in the page address in the address barType in the page address in the address bar Click on a Click on a hyperlinkhyperlink FavouritesFavourites remembers where web pages remembers where web pages

areare You jump You jump backback and and forwardforward between between

viewed pagesviewed pages HistoryHistory shows which pages that have been shows which pages that have been

visitedvisited

Online / OfflineOnline / Offline

Once your computer is connected up Once your computer is connected up and ready to send and receive and ready to send and receive information it is said to be information it is said to be onlineonline

When your computer is not ready to When your computer is not ready to send and receive information it is send and receive information it is offlineoffline

Internet Service Providers Internet Service Providers (ISPs)(ISPs)

To access the internet you need to have an To access the internet you need to have an agreement with an agreement with an internet service providerinternet service provider

You have to log on to your ISP’s computer to You have to log on to your ISP’s computer to access the internetaccess the internet

Your ISP Your ISP helps your browser find web pageshelps your browser find web pages gives access to web-based e-mail gives access to web-based e-mail provides access to newsgroups and chat rooms.provides access to newsgroups and chat rooms. provide space on their servers to store your own provide space on their servers to store your own

web pages web pages

How to choose a ISP?How to choose a ISP?

Points to considerPoints to consider

how much they how much they chargecharge per month per month how how reliablereliable the service is the service is how how longlong you can stay online you can stay online how how efficientefficient the service is the service is

Mobile Internet TechnologyMobile Internet Technology

This technology uses devices that let you This technology uses devices that let you access the internet while on the moveaccess the internet while on the move

All of the devices have All of the devices have mobile phone technology mobile phone technology a mini-browser a mini-browser internal memory internal memory a processora processor

Mobile Internet Technology Mobile Internet Technology DevicesDevices

Some are phones with a browser – smartphonesSome are phones with a browser – smartphones Some are palmtops with phone technology built Some are palmtops with phone technology built

in in They often have features such asThey often have features such as

touch screens touch screens WIMP HCI WIMP HCI mini browser mini browser calendar calendar a database a database a calculator a calculator mobile phone connection to access the internet as well mobile phone connection to access the internet as well

as make phone calls and send text messagesas make phone calls and send text messages

Services on the InternetServices on the Internet

World Wide WebWorld Wide Web (WWW) is made up of web (WWW) is made up of web pages that are stored on servers worldwidepages that are stored on servers worldwide

E-mailE-mail NewsgroupsNewsgroups and take part in discussions on and take part in discussions on

a whole range of topics a whole range of topics Chat roomsChat rooms are electronic groups that are are electronic groups that are

less structured than newsgroups less structured than newsgroups Search enginesSearch engines look for web pages look for web pages

Software on the InternetSoftware on the Internet

There is a wide range of There is a wide range of softwaresoftware that you can download from the that you can download from the internetinternet

They all have different They all have different agreementsagreements attached to themattached to them

FreewareFreeware

Free software but the author holds the Free software but the author holds the copyrightcopyright

You can use the software and even make You can use the software and even make copies of it and give them away to peoplecopies of it and give them away to people

You must not change the software or to You must not change the software or to sell it sell it

Device drivers for printers and CD-writers Device drivers for printers and CD-writers are examples of freeware as are some are examples of freeware as are some gamesgames

Shareware Shareware

Shareware software comes with a free Shareware software comes with a free 30-day trial period30-day trial period

After the 30 days you should register After the 30 days you should register and pay a fee or delete it from your and pay a fee or delete it from your computer computer

You can make copies of the software You can make copies of the software and distribute them to other peopleand distribute them to other people

The disadvantage of this system is The disadvantage of this system is that it relies on people’s honestythat it relies on people’s honesty

Commercial softwareCommercial software

Commercial software is bought Commercial software is bought across the counter in shops such as across the counter in shops such as PC World or through the internetPC World or through the internet

You are often limited to making one You are often limited to making one backup copy or simply are allowed to backup copy or simply are allowed to copy the software once on to your copy the software once on to your hard disk and keep the CD as a hard disk and keep the CD as a backupbackup

VideoconferencingVideoconferencing

Videoconferencing is using a computer network to Videoconferencing is using a computer network to send audio and visual data to enable people in distant send audio and visual data to enable people in distant locations to have face-to-face meetingslocations to have face-to-face meetings

A A point-to-point conferencepoint-to-point conference connects connects twotwo peoplepeople at at two different locations using simple webcams, two different locations using simple webcams, microphones and speakers attached to their microphones and speakers attached to their computerscomputers

Multipoint conferencingMultipoint conferencing links links severalseveral peoplepeople in distant in distant locationslocations

Sounds and images are captured by the microphone Sounds and images are captured by the microphone and camera. They are then transmitted across the and camera. They are then transmitted across the network, which can either be a LAN, a WAN or even network, which can either be a LAN, a WAN or even the internet the internet

Advantages of Advantages of Videoconferencing?Videoconferencing?

People who are located in different People who are located in different countries can have face-to-face meetings countries can have face-to-face meetings where they can discuss and make where they can discuss and make decisions decisions

This avoids travelling and staying in This avoids travelling and staying in hotels, saving time and moneyhotels, saving time and money

Teams of workers can be brought together Teams of workers can be brought together quickly no matter where they are locatedquickly no matter where they are located

Social IssuesSocial Issues

The internet is a rich source of The internet is a rich source of information on almost any subject information on almost any subject

This information can help you find This information can help you find work, be successful in school, work, be successful in school, business and leisurebusiness and leisure

Not everyone has access to this Not everyone has access to this informationinformation

Some people are at a disadvantageSome people are at a disadvantage

IsolationIsolation

People could isolate themselves from People could isolate themselves from others and spend most of their time others and spend most of their time communicating using computerscommunicating using computers

Over use could lead to people Over use could lead to people becoming detached from the world becoming detached from the world around them. around them.

We should keep a balance between We should keep a balance between using networks and keeping in touch using networks and keeping in touch with people face to facewith people face to face

Legal IssuesLegal Issues

People sadly use networks to commit crimePeople sadly use networks to commit crime hack into networks and steal or corrupt hack into networks and steal or corrupt

data data hack into networks and cause damage by hack into networks and cause damage by

leaving viruses leaving viruses commit fraud such as stealing money from commit fraud such as stealing money from

bank accounts bank accounts break copyright law by illegally transferring break copyright law by illegally transferring

software, data or other filessoftware, data or other files

PrivacyPrivacy

Some people disregard others’ right Some people disregard others’ right to privacy and use networks to send to privacy and use networks to send unwanted e-mails, chain-mail, unwanted e-mails, chain-mail, adverts, junk e-mail or spamadverts, junk e-mail or spam

Ethical issuesEthical issues

When we are looking at ethical issues we are When we are looking at ethical issues we are basically looking at right ways and wrong basically looking at right ways and wrong ways to use networksways to use networks

Networks are very powerful communication Networks are very powerful communication tools and, used properly, they can bring great tools and, used properly, they can bring great benefits to people and society in generalbenefits to people and society in general

Used irresponsibly, and for the wrong Used irresponsibly, and for the wrong purposes, they can spread bad feelings and purposes, they can spread bad feelings and disinformation, stir up hatred, be a source of disinformation, stir up hatred, be a source of crime and corruption and generally crime and corruption and generally undermine the bonds that hold society undermine the bonds that hold society togethertogether

Codes of conductCodes of conduct

Businesses and organisations have set Businesses and organisations have set out codes of conduct for network usersout codes of conduct for network users

These codes are called ‘Acceptable These codes are called ‘Acceptable Use Policies’ Use Policies’

They are based on the need to They are based on the need to respect other people, their rights and respect other people, their rights and

property property adhere to the lawadhere to the law