NetworksNetworksNetworksNetworks

. What is a network?

Standard Grade Computing StudiesStandard Grade Computing StudiesStandard Grade Computing StudiesStandard Grade Computing Studies

Stand Alone or Networked?

• A stand alone computer is one that is not connected to a network

• This could be a desktop computer or a laptop that has no wired or wireless connection.

What is a Network?• A series of computers linked together

so that they can send and receive data.• We use them for sending e-mails,

downloading files, shopping, etc

• You need to know about– Local Area

Network (LAN)– The Internet

<- What is a network?

Local Area Networks ->

Local Area Network (LAN)• Cover a small area such as one room or

building.– Our school has a LAN

• Each computer on a LAN is called a station

• One station is called the file server. – The file server is

where all the data & files are kept

<- LANs LAN Advantages ->

Advantages of a LAN

• Share data e.g. files in Our school folder

• Share devices attached to the network (like a printer)

• E-mail• Security ..Passwords ..Different

levels of access • You can log onto any station

connected to the LAN

<- LAN Advantages Ex 1 ->

Exercise 1

<- LAN Advantages Transmission meda ->

1.What is a LAN?

2 Describe your school’s LAN

3. Write down 3 advantages of a LAN

Transmission media for LAN

• Stations can be connected by cables or wireless technology

Cables:Coaxial cablesTwisted-pair Cabling

<- Ex1 Wireless ->

Optical fibre Uses light beams to transmit data at High speedsExpensive but doesn't get interference

Fibre Optic Cable• High speeds:

– Uses light beams to transmit data at High speeds { 100 terabytes per second is possible}

• Doesn’t get interference { unlike copper wire cable}

• More secure: – Difficult to intercept data on a fibre

optic cable• Expensive to install

Transmission media for LAN

•Wireless– Infrared communication

• Used for wireless mouse and keyboard

– Bluetooth• Range of about 10 metres

– WIFI (Wireless Fidelity Alliance)

• Range of about 12-50 metres

Bluetooth & WIFI use radio waves<- Transmission media NICs ->

<- Client/Server WANs ->

Exercise 2

1. Name 2 types of cable used in a network.

2. What type of cable does the school have on its LAN?

3. How can you link up the computers at home without using cables?

Client/ServerClient/Server• Clients are workstations• Servers are central

computers• Servers have:

– powerful processors– Large memory capacity

• Clients are workstations• Servers are central

computers• Servers have:

– powerful processors– Large memory capacity

<- NICs Ex2 ->

Client/Server

• The servers provide the resources for the computers { clients} connected to the network for example:

• Printer servers• File Server• Proxy server

Client/Server

• In a client server network it is possible to :– organise Security for the whole

network– organise Backups for all the data on

the network– control who can access the network by

setting up accounts {with IDs and passwords}

Peer to Peer network• In a peer to peer network there is

no central server.• The computers are linked together

to enable them to send and receive data.

• Each computer must back up its own data and organise its own security

Peer to Peer Network

Peer to Peer network• Since there is no centrally

organised security of backup system on a Peer to Peer network:

• They are only suitable for ‘trusting’ environments’ e.g. home use.

• They are not suited to commercial or business use.

The InternetThe Internet

• A network of networks• Can be accessed by any internet-

ready computer system.• You need:

– A telecommunications connection such as a modem or broadband

– A browser– A link to an Internet Service Provider

<- Ex5 Modems and Dialup ->

Transmission Media for The Internet

• The Internet uses Telecommunications links– It communicates information around

the world using:•Microwave transmission•Satellite links•Optical Fibre•Telephone cables

<- WANs Ex3 ->

Services on the InternetServices on the Internet

• World Wide Web• Newsgroups• Chat rooms• Search Engines• E-Commerce

< Ex 6 WWW >

BrowsersBrowsers

• Software that fetches and displays web pages

• Most people use Internet Explorer

• Hyperlinks let you click onto a new page

• The browser will remember web pages for you using favourites

<- Broadband Browser example ->

Hyperlink

Favourites

Forward and back buttons

History

<- Browsers Online/Offline ->

The World Wide WebThe World Wide Web

• Web pages stored in servers round the world

• Web pages are multimedia documents

• Linked with hyperlinks

< Internet services Hyperlinks >

Other services on the netOther services on the net

• Newsgroups let you discuss particular subjects

• Chat rooms let you talk live to other people

• Netiquette is very important when using these services

<superdave> I like rock’n’roll<megabrad> Dude what’s your favourite band????????1<superdave> like, Nirvana dude

<glasgowbob> haw naw m8 get a clue<megabrad> who is this glasgowbob?<glasgowbob> whit man watch oot<superdave> like whatever man<Teacher> hello chaps, what’s going on?<glasgowbob> aw naw teacher man, pure bolt

** glasgowbob has signed out

< Ex7 Newsgroup pic >

NewsgroupsNewsgroups

< Other services Search Engines >

Search EnginesSearch Engines

• Simple searches – just type in a brief description

Any search engine that you enter your brief description into a single search box uses simple search.

You can do this on:

•Google

•Yahoo

•Google images

< Newsgroups Search example >

Cloud Computing• Instead of buying and setting up

a network, they have simple computing devices:

• Which they use to access the internet

• And use the software, backing storage and servers provided by the Cloud Computing company.

• Basically, they rent the use of powerful network resources

Cloud Computing: advantages

• Cloud users:• can have access to powerful

networks without having to spend lots of money setting up their own network = lower cost

Cloud Computing: advantages

• Cloud users:– can update and change their software

as their needs change = flexibility– have access to technical support =

lower maintenance / staff costs– are billed only for the services they use

and the length of time they use them == lower cost

– can easily scale up or down their network resources as their needs dictate =flexibility

Cloud Computing: advantages

• Backup and recovery of data is guaranteed by the Cloud Provider

Cloud Computing: disadvantages

• Security: having all an organisation’s data stored in ‘ the cloud’ can be a security risk e.g. from hackers, from malware– Many organisations keep ‘critical data’

backed up locally, just in case.

• It depends on a reliable speedy internet connection

• Can be locked into a contract

Locally owned and managed network

• Gives local control over – Security– Backup regime

• But– Can cost a lot more to set up– Is not as flexible: not so easy to scale

up or down the hardware and software