compy8_2_ - lady lumley's school web viewwifi – typically 54mbs, ... demonstrate how to...

LLS ICT Dept 2014-15 Year 8 - Computing

Computing Y8: Unit 2 - Networks

Overview for Students:Students learn about the Internet; local and wide area networks. We look at different types of network and how to encrypt data to keep it secure.

Summary:This is a theoretical unit covering the basic principles and architecture of local and wide area networks. Pupils will learn that the World Wide Web is part of the Internet, and how web addresses are constructed and stored as IP addresses. Client-server, peer-to-peer networks and the concept of cloud computing are all described. Ways of keeping data secure and simple encryption techniques are also covered. In the final lesson, pupils will sit a multiple choice test which will form the Unit assessment.

This unit will form very good preparation on the topic of networks at GCSE level.

New Attainment Targets (partially covered in this Unit):Understand the hardware and software components that make up computer systems, and how they communicate with one another and with other systems

Understand a range of ways to use technology safely, respectfully, responsibly and securely

Previous Learning:No previous learning is necessary with this unit.

Suggested Resources:Worksheets 1 to 5, and the Packet Switching Resource Sheet.

Vocabulary: Internet, World Wide Web, URL (Uniform Resources Locator), IP address, protocol, wide area network, local area network, data packets, packet switching, domain name, client-server network, peer-to-peer network, cloud computing, encryption, decryption, plaintext, cipher text

Assessment:Pupils will sit an end-of-unit test. It is expected that teachers will map the results onto their own school assessment structure for Computing and ICT.

The answers to the test are also included and should be removed from the folder before uploading to a file area with pupil access.

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HML (100mins)LOs (BTEL)

Activities Home Learning and Portfolio Evidence

Teacher Notes

Lesson 1 : first half assessment of previous unit / Networks (1): The InternetI will learn what the Internet and World Wide Web are

I will learn how web addresses are constructed

I will learn what a protocol is and why one is needed for data communication

I will learn how packet switching works

I will learn what the Domain Name Server (DNS) does

Previous Unit Assessment------------------------------------------------------------------------------------------------------------

As a starter activity ask students to come up with a definition of the Internet.

Explain the world wide web is just a part of the Internet. VoIP, Email and instant messaging, for example, may use the Internet but not the world wide web.

Introduce pupils to the term ‘URL’. Discuss the various parts of a web address and different domain names.

Give out Worksheet 1 Domain names or let the pupils access a digital copy. They can complete Activity 1 and will complete the rest as the lesson progresses.

Explain why HTTP is needed and introduce the concept of splitting data for transmission into data ‘packets’. It’s fairly remarkable that the whole world managed to agree on a single set of rules! What if we could all use the same currency or speak the same language?

Explain how packet switching works using the Packet Switching Resource Sheet. Using this, you can role play the job of routers and the packet switching process from sender to receiver. You can also explain that images are sent in the same way as text; the image is split into chunks and sent as packets too.

An IP (Internet Protocol) address is a numerical label assigned to each device connected to the Internet. These used to be 32-bit numbers, giving a possible total of 232 different addresses (about 4.3 billion), but we are running out! The enormous growth of the Internet led to a new protocol being introduced (IPv6) which allows 128 bit addresses, about 3.4x1038 addresses. (About 340 billion billion billion billion unique addresses – more than enough for everyone on the planet to have 50 billion billion billion billion each!)

Explain that a Domain Name Server is used to convert each URL into its unique IP address. URLs are only required because we find it too difficult to remember web

HL1 - Complete previous unit assessmentHL2 - Worksheet 1 Domain names: Activity 1

Give out pink copies of lls ict 8_2 SASt Networks 2014-15 pink v1.xlsx (Fronter Resources)Slides for 8_2 Networks L1 - The InternetPrint out the Packet Switching Resource Sheet, and absorb its contents. You may like to print out two or three copies of the second page so that you can repeat the exercise if necessary. Think up a suitable sentence which you can divide up into 8 packets. You can complete the packets and cut them out in class; don’t forget to bring a pair of scissors

Packet Switching Resource Sheet

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addresses as long strings of numbers. Demonstrate finding the IP address for Google using www.who.is or Link Who Is DNS Lookup. Copy the IP address you find into the address bar of a browser and show the pupils what happens.

Pupils can test out the system themselves in Activity 2 of Worksheet 1 Domain Names.

Videos: Link How the Internet Works provides a good summary of the lesson. Link DNS gives an animated overview of how the DNS works.

Extension activityAsk pupils to complete Activity 3 of Worksheet 1 Domain Names. Here they can use a website such as www.uk2.net to search for a domain name to check its availability.



Teacher Notes

Lesson 2a and 2b - Connectivity (2) and Topologies (3)I will learn the meaning and significance of bandwidth

I will learn to compare different types of cable, and the relative speeds of data transmission

Calculate time taken to download files of different sizes at different bandwidths

Understand what is meant by buffering and why it is used

Understand the difference between LANs and WANs

Know what extra hardware is needed for a LAN to operate

As a starter, you could ask the class how data is transmitted across the Atlantic or the Pacific Ocean. They may not realise that it is by under-sea cables. You could tell the class a little about the history of cable-laying.

Show the class the map of under-sea cables. You could also demonstrate this with an interactive version using Link Undersea Internet Cable Map. Occasionally these cables are damaged or severed, sometimes deliberately, cutting off large parts of the world from the Internet. Divers were reportedly caught cutting the cable off the coast of Egypt in 2013. Users of the Internet in Egypt reported slower connection speeds afterwards.

HL1 - Worksheet 2 Transmission Speed

HL2 - Make list of all wired and wifi devices at home. Find out your ISP and type of broadband. List all wired devices and wire-less devices.

Slides for 8_2 Networks L2a - Connectivity

Slides for 8_2 Networks L2b - Topologies

Link Google Data Centres

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Identify three different network topologies – bus, ring and star

Explain the meaning of bandwidth. One analogy for bandwidth is to compare it to the amount of water that can flow through various sized pipes at any one time. The water (or data) flows no faster, but more can flow at once.

Demonstrate an Internet speed test using Link Internet Speed Test. Depending on timing, pupils may like to have a go? – Downloading is generally faster than uploading. Internet providers give prior this too. Ask them why the upload and download speeds are so rity to downloading because most users spend far more time downloading than they do uploading.

Explain broadband and fibre optic cable. Find some cables to pass around.

Ask pupils to calculate the time it takes to download different sized files at various speeds. (See “Calculating download speed” on PP slide)

CSH - Draw 8 blocks on the board. Each is a megabit. Talk about kilo and mega. 8 bits to a byte. Got thro the questions:

8 Megabits per second / 8 bits = 1 megabyte per second = 1 second

10 seconds

700 seconds or 11m 40s

2800 seconds or 46m 40s

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Sending data: The graphic in the PP slide shows CAT5 cable, fibre-optic, WiFi and Coaxial cable (aerials), which is now becoming obsolete. . If there is time, you can ask pupils to find the transmission speeds of various types of cable. E.g.

Fibre Optic Cable transmits data as pulses of light with speeds of up to 10Gbs or more

Coaxial cable – max 100Mbs, sent as an electronic signal

WiFi – typically 54Mbs, sent as a radio signal

CAT5 – 100-1000Mbs, sent as electronic signals

(http://www.ni.com/white-paper/13724/en/)

Before cables and internet technology, pigeons were frequently used for carrying data. Paddy, an Irish WW2 (‘broadband’) pigeon was even decorated with the Dickin Medal "For the best recorded time with a message from the Normandy Operations, while serving with the RAF in June, 1944"!

Pembroke House, a school in Kenya, used homing pigeons in the 1950s to carry cricket scores back to the school during away matches. When the team was playing away, say at Nakuru, 25 miles away, or even Nairobi, 50 miles,

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they would take a basket of pigeons with them and at intervals during the match, scribble a message, attach it to a pigeon and release it. Pigeons would arrive back and messages such as 'Higgins out for duck' or ‘St Brendan’s 46 for 7. Three overs left’ would be eagerly read. This worked very well apart from the occasional bird going astray, and also the hazard of Augur buzzards, which devoured some of the birds along with their messages.

Explain the advantages and disadvantages of using a wireless connection. Give out Worksheet 2 Tramnsmission Speed and ask the pupils to complete it.

Introduce ‘buffering’. Most pupils will have experienced delays caused by buffering when watching videos online. What caused it? What was their connection speed? What was the connection type they were using? How large was the file?

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As a starter, hold a class discussion about the advantages and disadvantages of standalone vs networked computers, say in a school. Advantages: can share devices such as printers, scanners, external drives. Easy to share folders and files of data. Backup is taken care of centrally.

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Disadvantage: security is harder to control. If a network shares one Internet connection this can slow down the speed of downloading. More costly to run as the LAN needs to be on all the time. It is more complex to maintain a network.

Explain the difference between a WAN and a LAN.

Discuss the extra hardware needed to operate a LAN. Show the example of a Network Interface Card (NIC) and explain that all computers need one to connect to any network. These include desktop computers, laptops, tablets and mobile phones.

Identify the three common network topologies: bus, ring and star and then ask pupils what they think might be the advantages and disadvantages of each.

Explain that some networks will require additional pieces of hardware such as routers, hubs and switches. Describe the differences between them.

As an exercise, pupils can design the network layout for their school, using icons to represent server, hub, switch, router, Internet, workstation, printer etc. See Worksheet 3 Designing a network.-----------------------------------------------------------------------------------

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Teacher Notes

Lesson 3 : Register whilst download W/S 3. Research actual transmission speeds for CAT 5 and optical fibre.Check W/S 2 done. Check list of wired and wireless devices. Go through worksheet 2. CSH Get them to hold up something of each colour to vote for which is which on the slide. Discuss results of research.

Discuss home networks on board with their lists out.

Demonstrate how to use Word Drawing Canvas and link icons.

Draw Home network.

Take them through School Network.

HL1:

2. Add a Key / Name and Title "My Home Network" and complete3. Complete a new word doc for "My School Network"

Notes3 servers - SIMS / Student Data / Staff DataInternet / Firewall / Router / SwitchesOne switch and Terminal and printer per classroom (put number of PCs beside)IT1, IT2... IT6Library

One switch and Terminal for just ONE classroom (??)One switch and Terminal for ONE Office (??)Assembly Hall

Give

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Teacher Notes

Lesson 4a and 4b – Client-server (4) Networks and Encryption (5)Understand what constitutes a client-server network

Understand what is meant by cloud computing

To identify some of the types of data that need to be kept secure

To learn how unauthorised people can break ciphers and read encrypted data

To learn some classical encryption techniques

Starter: discuss what is meant by a client/server network. Ask if pupils have ever used one. (Yes: school network!). Clarify what a server is, and that there may be different servers each with different functions, or in a smaller network, just one server doing everything – acting as file server, email server, print server etc.

With reference to the last lesson, point out that star and bus networks are both client-server networks. Client-server networks could be either LANs or WANs.

Discuss the example of a computer network in a hospital – what different types of user will there be? Will everyone on the network be able to see all the data? How is this prevented?

Discuss the advantages and disadvantages of a client-server network.

There are other advantages apart from those on the slides – for example software licences can be controlled and software updated centrally.

Peer-to-peer networksContinue with a discussion of peer-to-

HL1 - Worksheet 4 Client-server networks

Answer sheet is PP in the folder Fronter Resources. Usual ICT password to open.

HL2 - Worksheet 5 Encryption

Slides for 8_2 Networks L3a - Client-server networks

Slides for 8_2 Networks L3b - Encryption

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peer networks. Do any of the pupils have two linked computers at home?

Peer-to-peer (P2P) networks have been at the centre of the file-sharing controversy, highlighting sites such as Napster and Pirate Bay in recent news. These sites enable file sharing and can encourage illegal sharing of copyright material such as music and software applications. Several of these sites have been ‘shut down’ after courts have ruled them illegal. Their owners have even been sentenced to prison. However, they keep springing back up since it is very difficult to control a P2P network as there is no central store of data.

If time permits, pupils could research news articles online about these file sharing or ‘torrent’ websites.

Give out Worksheet 4 Client-server networks and let pupils work on it individually or in pairs.

Cloud computingIn cloud computing, instead of software applications and data being held on your computer or a LAN server, they are held on the network of computers that make up the “cloud”.

The only thing a user’s computer needs is the cloud computing system’s interface software – for example, a Web browser such as Chrome or Internet Explorer.

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To quote http://computer.howstuffworks.com/5-factors-cloud-data.htm,“If you want to start a document on your laptop and revise it on your phone, you can. If you'd like to listen to your music library from either your tablet or your work computer, you can do that, too. Gone are the days of being tethered to a single device. The reason for this: the cloud.Simply put, cloud computing involves storing data and applications on remote servers and accessing them via the Internet rather than saving or installing them on your personal computer. You can use the cloud to house text files, photos, videos, music and the like, either as primary storage or backup storage, often for free or for a nominal price.But the cloud isn't just about storage. In this age of Web mail, social networking, online bill paying, automatic phone backups, multiplayer online gaming and video streaming, a lot of us are already performing a variety of personal and business activities in the cloud, whether we realize it or not.”

Discuss the ability to remotely control the heating, lighting and music in your home. (See screenshot of British Gas remote control heating – simply turn up the heat when you land at the airport in February at the end of your holiday!)

Ask pupils what they think are the

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disadvantages of Cloud computing?

There are several impressive and high quality photographs of Google’s server farms and cooling systems available at Link Google Data Centres. These help give some scale to server use and the Cloud.

Plenary discussion: Why have your word processing and spreadsheet software on your home computer? In the future, will we have small hard disks and keep almost all data and applications on the cloud?

As Cloud computing grows, will computer use and ownership become cheaper?

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Starter: Discuss the padlock symbol found on banking and shopping websites. When a small padlock appears in the browser search bar, it means encryption is switched on. This is one way that organisations can keep data transmitted over the Internet secure from hackers.Refer to the http protocol and ask what the ‘s’ of https might stand for. Discuss the questions on security in the PowerPoint guide.EncryptionGo over the terms used, i.e. plaintext, ciphertext, encryption, algorithm, key.How can a message be decrypted by

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someone who does not know the key? Decoders at Bletchley Park in WW2 had the difficult job of decoding messages, with a key that changed every day.Explain the two approaches to code breaking: the brute-force attack and the cryptanalytic attack where a logical approach is used to work it out.Explain that using statistics, you can begin to guess which letters may have been substituted with which others based on the frequency of their occurrence.Show how different ciphers work, e.g. the Caesar Shift cipher, or substitution key depending on a key word – ‘jellybean’ is given as an example. The key word or phrase could change with every message, so even if one message is deciphered it will not mean that the cipher is broke. For example, the message could start with the page number of an agreed book, and the key word could be the first n letters on that page.Give out Worksheet 5 Encryption.If there is time you can introduce the concept of using prime numbers in modern cryptographic methods – the details are too complex to cover. Can anyone find the two prime numbers that make up a given number – say 21 (=3 x 7), 143 (= 11 x 13), or 217 (= 31 x 7)? It’s easy to see that with a number of several million digits this would take even the fastest computer a very long time!

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Computing Y8: Unit 2 - Networks--------------------------------------------------------------------------------Pupils should complete the Assessment Test. Answers are available in the Networks Assessment Answers sheet.These tests may be printed or answered in the document at a computer by highlighting the correct answer or changing it to bold text.Pupils might upload an offline test to an area for teacher assessment online. This could be an MLE such as Fronter, Frog, SharePoint or Moodle.

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Teacher Notes

Lesson 4: Assessment / first half of next unitBe able to apply their knowledge in answers to a range of questions.

Be able to highlight areas of strength and any gaps in their understanding of computers.

Pupils should complete the Assessment Test. Answers are available in the Networks Assessment Answers sheet.These tests may be printed or answered in the document at a computer by highlighting the correct answer or changing it to bold text.Pupils might upload an offline test to an area for teacher assessment online. This could be an MLE such as Fronter, Frog, SharePoint or Moodle.--------------------------------------------------------------------------------Start next unit

Complete SAS

HL2 - next Unit HL

Networks Assessment Test

Networks Assessment Test Answers

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--------------------------

-MissingWorksheet 5 Encryption

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Networks Assessment Test

Networks Assessment Test Answers

Acknowledgements

Every effort has been made to trace the holders of copyright material used in the PowerPoint Guides and we apologise in advance for any unintentional omissions. We would be pleased to insert the appropriate acknowledgement in any subsequent edition of this publication. With thanks to the following: Network icons from www.icons8.com, Undersea cable map from Google Map Data, INEGI 2013, Server room image in Council Bluffs, Iowa, Google/Connie Zhou. This material contains links to relevant websites featured in the teacher’s guide. Every effort has been made to ensure that at the time of distribution, the links remain unbroken, the material remains up-to-date and that links are not inadvertently linked to sites that could be considered offensive. PG Online cannot be held responsible for the content of any website mentioned in this material. It is sometimes possible to find relocated sites by typing the original URL into a browser. Any errors should be reported directly to [email protected] and changes will be made in any subsequent editions of the material.

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compy8_2_ - lady lumley's school web viewwifi – typically 54mbs, ... demonstrate how to...

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