Computer Networks GCSE ICT - PowerPoint Presentation

Slide1

Computer Networks

GCSE ICTSlide2

Learning Outcomes:

Understand what a network is.

Identify types of networks.

Explore types of network formations.Slide3

Networks

Networks are two or more machines linked together to share files

At

home, your computer might be connected to its own printer and scanner. This works well as you are the only person who will be using them. A computer which isn't connected to a network is known as a '

stand-alone

'

In

a school or an office, it would cost a lot of money for every computer to have its own printer and for the majority of the time, like your printer at home, it wouldn't be used.Slide4

Networks

By joining computers together to form a network, they are able to

share one printer

.

This

means that more money can be spent buying a better quality printer and that the printer is being used much more of the time.

As well as sharing hardware, a network allows computers or users to

share software and data

.

A

computer connected to a network is known as a

'work-station'

The computers can

be connected by

cables or Wireless

.Slide5

There are two main types of Network…

LAN and WANSlide6

LAN – Local Area Network

Server

Printer

Scanner

WorkStation 1

WorkStation 3

WorkStation 2Slide7

LAN – Local Area Network

When the computers are fairly close to one another say, in a single office building, the computers

then form a

Local Area Network (LAN)

.

Once

the computers are connected together into a LAN, many people (users) can share and use the same resources at the same time.

They

can share files, software, hard disks and peripherals such as a printer or CD-ROM

.

Users

can also use the LAN to communicate with each other by

e-mail. Data can be transmitted very quickly between networked computers.Slide8

LAN – Local Area Network

A

file server

is

used

to store each person's data

and their files

. This means that people can log onto any machine on the network and access their files.

They are not restricted to just one machine. Another advantage of having all of the files stored in one place is that a

back up copy of every users files

can be made easily.

To log onto a LAN, you usually need a

user name and password. The user name identifies you to the file server so that it can 'serve' you the correct files. Slide9

Networks: LANs

File Server :

Runs software, stores files.

Terminals :

Workstations that give network access.

Print Server :

Queues up all print jobs from users in network.

Cables (wire/optic) :

Sends

data

Switch/Router

– direct data packets

What hardware do you need for a LAN network?Slide10

ADVANTAGES OF

NETWORKS

Programs

can be shared

- software packages can be installed onto the file server and accessed by all individual workstations at the same time. This reduces cost, maintenance and makes upgrades easier.

You can

access your work from any workstation on the network

. Very handy if you have to change computer every time you go to a different classroom.

Data can be shared

by all users at the same time. Many people can access or  update the information held on a database at the same time. Thus information is up to date and accurate.

Users can communicate with others on the network by sending messages and sharing files. Slide11

More Advantages

…

Individual workstations do not need a printer

, one high quality printer can now be shared by everyone, thus cutting costs.

Networks provide security

. A user must have the correct Password and User ID in order to be able to access the information on the network.

Private areas on the network can be set up

that allows each user to store their personal files. The only other person who can access these files is the 'system administrator' who looks after the network

.Slide12

DISADVANTAGES OF

NETWORKS

Networks can be expensive to set up

. They often involve taking up floors and ceilings to lay hundreds of metres of cables - the File Server needs to be a powerful computer, which often means that it is expensive. Plus they need expert staff to look after them.

Networks are vulnerable to security problems

. Hackers, disgruntled employees or even competitors might try to break into the system to read or damage crucial information.

If the main

File Server breaks down

, then the

whole system

becomes useless and no-one can carry on working. As the number of users increase on the network, the performance of the system can be affected and things start to slow down.Slide13

Task 1 - Exam Questions

You have Five minutes to answer the following:

Q1-Identify two disadvantages of setting up and running a computer network (2 marks)

Q2-Discuss the different methods used to prevent people from gaining unauthorised access to a computer network (3 marks)Slide14

Exam Answers

Q1- Any two of the following points:

-Networks can be expensive to install in terms of cable and hardware such as routers and switches

-Usually need specialist staff to run the network

If the network is busy, accessing files and hardware might be slower than a standalone machine Slide15

Exam Answers

Q2- Any two of the following points:

Username

Password

Access rights

Firewall

Restrict physical access e.g. lock doors, security cameras Slide16

Task

Two - Complete the worksheet:

Fill in in the Gaps

List Advantages and DisadvantagesSlide17

Network Topologies…

Slide18

Bus Network

This is one method of connecting computers together and is the simplest one to connect together.

A single cable joins all of the workstations, printer, file server and other components together.

At each end of the bus is a 'terminator'. This is a piece of hardware which prevents signals bouncing back and forth (echoes). Slide19
Slide20

Advantages and Disadvantages

Advantages

Easy to install.

Easy to add extra workstations.

Uses less cable than a Star network.

Best choice for temporary networks.

DisadvantagesIf there is a problem with the central cable, the entire network stops working.

If there are a lot of workstations on the network, data can travel slowly.

Data collisions can happen as the network becomes busy.

Low security - every workstation can see all of the data in the network.

Limited cable length and a maximum number of workstations.Slide21

Ring Network

In a ring network layout, all of the computers are connected to one another in a circle. The data passes from one computer to the next one and then all the way around the ring layout until it reaches the destination computer. Slide22
Slide23

Advantages and Disadvantages

Advantages

Transmission of data is fairly simple as it only travels in one direction.

No data collisions.

Extra computers can be added easily with little effect on performance - although you have to shut down the network to be able to do this.

Disadvantages

If a single machine is switched off, the network doesn't work.

If a cable breaks, the network doesn't work.

Data must pass through every computer until it reaches its destination. This can make it slower than other network layouts.

If there are any problems with the network, they can be difficult to identify the cause. Slide24

Star Network

In a star network layout, each workstation is connected by its own cable directly to the server. Star networks are usually the layout of choice in schools and offices because they tend to be the most reliable of the topologies.Slide25
Slide26

Advantages and Disadvantages

Advantages

Star networks are very reliable. If one connection fails, it does not affect other users.

Very few data collisions as each workstation has its own cable to the server.

Good security - no workstation can interact with another without going through the server first.

Disadvantages

The most expensive network layout to install because of the amount of cables needed.

Installing the network usually needs experts to set it up.

Extra hardware such as hubs and switches may be needed.

If the server crashes or stops working then nobody will be able to access their files or use the network. Slide27

Task 3 - Exam Questions

The Manager of a Hospital is thinking about installing a network so that different departments can share data..

Write the minimum of a paragraph what network topology the hospital should buy. You should think in terms of cost, installation, efficiency and security

. Explain your reasons.Slide28

Intranets and Extranets

Intranet

is similar to the Internet but is internal to an organisation. An

INTERNAL NETWORK

Users access the Intranet through a user

name and password

Enables users to

share information

and communicate via

electronic messaging

View pages like webpages – like an internal websiteAn Extranet can be accessed from outside the Intranet by authorised users via a user name and password. A NETWORK that can

accessed EXTERNALLY.E.g. VLESlide29

The Manager of a Hospital is thinking about employees having access to the network internally via an intranet and externally via an extranet.

Write the minimum of a paragraph what the advantages and disadvantages of having an intranet and extranet. Give reasons.

Intranets and ExtranetsSlide30

Wireless Networks

Describe what is meant by the term WIFI.

What are the main components of WIFI?

Explain (in as much depth as possible) how a wireless network works.

List and describe Advantages and Disadvantages of using a Wireless networkSlide31

Task 4 - Complete the worksheet

Complete the work sheet describing Advantages and disadvantages of Network TopologiesSlide32

WAN –

Wide Area NetworkSlide33

WAN – Wide Area Network

Many modern companies have offices, shops or factories in various locations around the country, and for large corporations, across the world. Even though staff work in different places, they often need to be able to access the same information no matter where they are.

It would not be possible to connect computers in different buildings or countries together using LAN cables. Slide34

WAN – Wide Area Network

Computers on LANs in one building can be connected to computers on LANs in another building usually through the telephone system, often using a

modem

. They can also be connected via

fibre optic

cables

or satellite. By linking LANs together, the network is no longer local to one building, it is now spread over a wide area. It is known as a Wide Area Network (WAN)

The largest

WAN in existence is the Internet

?

Slide35

Networks: WANs

What extra hardware do you need for a WAN network?

Modems :

To connect up to a telephone system (instead of cable).

How a modem works…Slide36

Protocols

Computers

on a network must all have a way of being able to 'talk' or 'communicate' with one another and they do this by following a

protocol.

A

protocol is a set of rules which define

:How

to establish communication between the machines

The

format of any data which is to be exchanged between the machines

How errors in the data will be detectedHow errors will be correctedMethods of compressing the data to transmit it faster and more efficientlyHow the connection between the machines is to be terminatedSlide37

Protocols

The protocol that is used on most LANs and the Internet is known as the TCP/IP protocol.

If

any computers on the Internet are not using this standard then they will not be able to communicate with others that are.

Another

extremely common protocol in use on the web is HTTP - Hyper Text Transfer Protocol. which is what most page URLs start with. See what you can find out about this.Slide38

Research

Use the internet and your books to write an explanation of TCP/IP

Use the internet and your books to write an explanation of

HTTPSlide39

Task 5 -

Complete the worksheet

Complete the task 5 worksheet using the internet or your books to find the description of the

different Network

Components.Slide40

Network Communications

GCSE

ICTSlide41

Learning Outcomes:

Understand the

term

Bandwidth.

Learn

the different ways we can

communicate on a network

.

Know

how we connect to the Internet and what is required.Slide42

The Telephone Network in Computing

A modem is required for a computer to communicate over telephone lines

Data is converted from digital to analogue and then back again

The speed at which data is transmitted and/or received is measured in

bits per secondSlide43

FAST BANDWIDTH

SLOW BANDWIDTH

Network Communications

Bandwidth tells us the rate at which data can be transmitted down the communications line in a given period of

time.

The

current standard is 56,000 bits per secondSlide44

Network Communications

The

higher

the bandwidth, the

quicker

the data will flow along the line

…

Web pages loaded quicker.

Multimedia is downloaded faster.

Internet connection is faster.

Less network traffic. Quicker response time.Slide45

Network Communications

There are a number of connection types available to us when we want to access the services from the Internet… Each one has a different BANDWIDTH

.

PSTN : Public Switched Telephone Network.

ISDN : Integrated Services Digital Network.

ADSL : Asymmetric Digital Subscriber Line.Slide46

Public Switched Telephone Network

PSTN for short.

Uses traditional telephone system to allow access to the Internet

. This is the telephone system used for making day-to-day telephone calls

It is the main reason why computers have become so popular in recent years!

Low

Bandwidth

Dial

Up Connection.Slide47

Integrated Services Digital Network

ISDN for short.

Has a greater range of frequencies than PSTN, at least as twice as fast. Typical transfer rate of 128,000 bits per second

Data is transmitted simultaneously

Special connection and modem required

Supports Videoconferencing, faxes and voice applications.Slide48

Asymmetric Digital Subscriber Line

ADSL for short.

Usually referred to as

‘Broadband.’

Is permanently switched on, no need for dial

up to get a connection.

Uses telephone lines to transmit data at very fast speeds (512,000 bits per second)

ADSL modem and splitters required to separate telephone signal from the ADSL signal

Has

a high bandwidth.You can still make telephone calls when surfing the web!Slide49

Connecting to The

Internet

Single users can connect to the Internet

. Special Hardware

and Software

is required to allow people to access the Internet.

As well as

an electronic device (PC, Tablet etc.) you need:

Internet Service Provider.

Browser

Software. Telecommunications line e.g. ISDN, ADSL. Modem/Broadband Modem/ISDN adapter.Slide50

Network Security

GCSE ICTSlide51

Learning Outcomes:

Understand how to secure a network.

Understand Dangers posed to networks.

Identify different types of security.Slide52

The Basics

There are many ways to secure a network ranging from complicated around the clock security services to a simple lock and key.

Security is now a major item in every network it can mean the difference between life and death for some businesses.

Example: The play station network, was taken down by hackers and some of their customers credit card details stolen. This was all because the security on this network was weak or unprotected. Slide53

Network Security

Physical security

means that the hardware of the network is protected from theft and kept safe

.

Access security

means that there is a limit to the amount of access a user has to the information held on the network.

Data

security

means that there are measures taken to prevent the loss of data held on the system.Slide54

Ways of protecting you and your computer and network

There are now many company's offering users different packages to protect and prevent your computer and or network.

Most of theses packages detect, quarantine and delete infected files And some monitor the websites accessed and links to other servers and or networks.Slide55

Types of virus

There are many types of virus for example there are:

Worm virus

Trojan houses virus

Boot sector virus

Macro virus

Root kit virus

Time bomb virus

Memory resistant virus

Polymeric virus Slide56

Physical security for a network

As well as security software you will need to protect your network in more conventional ways i.e. lock and key.

Fire protection- fire doors, smoke doors, fire proof safes est.

Alarms-rooms containing the server should be alarmed

Locks-all rooms with services inside and have limited recorded access to them

Visibility-avoid putting computers on ground flour and where they are visible to passes byeSlide57

Data security

There are many ways to prevent loss of your data:

Password protecting your data.

You can also set the information as read only so it can not be tampered with.

You can also back up data either as a hard copy of saved digitally.

You will also need to keep a log on access to your server, so that if the worst happens you can trace the perpetrator.