The shape of the lesson
By the end of the lesson, learners can
- Why network?: Every networking question starts here: what does connecting the devices actually give you?
- Client-server and peer-to-peer: The two models differ in where the data and the services live.
- Thin and thick clients: Within the client-server model, clients differ in how much work they do themselves.
- LAN vs WAN: area covered and who owns the infrastructure.
- Client-server: central server provides services; central security and backup; single point of failure.
- Peer-to-peer: every peer is client and server; cheap and simple; no central control.
- Thin vs thick: where the processing and storage happen, and whether it works offline.
One picture every idea returns to
A network lets devices share resources, data and communication. A LAN covers a small area (one site) and its infrastructure is owned by the organisation; a WAN covers a large geographical area and uses infrastructure such as telephone lines and satellites leased from others. In the client-server model, clients send requests to a central server that provides a service and holds the data. In the peer-to-peer model there is no central server: every peer is both a client and a server. A thin client depends on the server for processing and storage; a thick client does most of its own processing.
Forty-five minutes, phase by phase
| Time | Phase | What happens in the room | Grouping |
|---|---|---|---|
| 0 to 5 min | Hook: predict | Open with the question in the title, Computers that share.. A single computer is useful; computers that can talk to each other are far more useful. Put the figure on the board: it is the one picture every idea in the lesson returns to. | Whole class, then pairs |
| 5 to 13 min | Teach and check: Why network? | Every networking question starts here: what does connecting the devices actually give you? | Whole class, then pairs |
| 13 to 21 min | Teach and check: Client-server and peer-to-peer | The two models differ in where the data and the services live. Model the worked example Justify a model on the board, one line at a time. Your turn: Three friends want to share music files between their laptops at home without buying any extra equipment. Which model suits them, and why? | Pairs |
| 21 to 30 min | Teach and check: Thin and thick clients | Within the client-server model, clients differ in how much work they do themselves. Your turn: A company wants to cut hardware costs and install software updates in one place. Its office has a fast, reliable network. Thin or thick clients? | Jigsaw |
| 30 to 36 min | Check | The four Stage 1 questions from the student lesson, answered on mini whiteboards or by show of fingers. Re-teach the one most get wrong. | Individual, then whole class |
| 36 to 43 min | Plenary | The exam-style questions from Stage 2, one at a time: thirty seconds alone, then a random call. The feedback lines in the key give the examiner's wording. | Individual, random call |
| 43 to 45 min | Exit and homework | Set the worksheet below (6 questions, 21 marks). Learners self-assess against the objectives before they leave. | Individual |
Protect the parts that carry the learning
The sequence carries about fifty minutes of material, so the lab is driven by one student while the class predicts rather than explored freely. Times are a guide.
Protected: the check at 30 minutes. It is the only individual read on whether the key idea landed, and it is not cut.
Cut first if the build overruns: the last check in Thin and thick clients, never the check or the plenary.
In a 60 minute block: run worksheet questions 1 to 3 in class as a Rally Coach set and model both the hardest worked example and its check live.
Jigsaw
Split the content into expert pieces. Expert groups master one piece each, then regroup so every home team has one expert per piece, and each expert teaches their piece to the team.
The full structure, with its variations and the other twelve, is on the cooperative-learning page.
What to head off, and how
| Trap learners fall into | Teaching move that pre-empts it |
|---|---|
| "A WAN is a big LAN" earns nothing. | Give the defining differences: geographical area covered, and who owns the infrastructure (a LAN's is owned by the organisation; a WAN uses leased or public communication links). |
| Always tie a justification to the scenario. "Client-server is more secure" is weak; "the patient records are on one server, so access rights and backups are managed centrally" earns the mark. | Return to Client-server and peer-to-peer: ask a pair to state the correct version and show it on the lab before moving on. |
| Thin and thick describe the client, not the server, and both still exist inside a client-server network. | A thin client is not "a client with a slow connection". |
LANs, WANs, client-server and peer-to-peer: worksheet
6 questions, 21 marks. Written in the style of the papers; no past paper question is reproduced.
Give three benefits of connecting the computers in an office to form a network.
Describe two differences between a LAN and a WAN.
Explain the roles of the computers in a client-server network, and how these differ in a peer-to-peer network.
A small charity has 4 computers in one room. It has very little money and no technical staff. Recommend a network model and justify your choice.
A university is replacing its library computers. They are used only to search an online catalogue and to run web-based applications. Discuss whether thin clients or thick clients are more suitable.
A student says: "Client-server networks have no drawbacks because the server does everything." Give two drawbacks of the client-server model.
Answer key and marking notes
- Hardware such as printers and the internet connection can be shared.
- Data and files can be shared and stored centrally, so everyone uses the same version.
- Users can communicate (email, messaging) / backups and security can be managed centrally.
- A LAN covers a small area such as one building or site ...
- ... whereas a WAN covers a large geographical area such as several countries.
- A LAN's infrastructure is owned by the organisation ...
- ... whereas a WAN uses communication links leased from or provided by third parties (e.g. telephone lines, satellites).
- The server provides services/resources (e.g. stores files, manages printing, authenticates users).
- The clients send requests to the server and use the services it provides.
- In peer-to-peer there is no central server.
- Each peer can both request resources from and provide resources to other peers.
- Peer-to-peer.
- No server needs to be bought, so it is cheaper.
- It is simple to set up and run without a specialist network manager.
- With only 4 computers, the lack of central management and slower performance as it grows are not significant.
- Thin clients are suitable because the tasks need little local processing.
- Thin clients are cheaper and software is updated once, on the server.
- However, thin clients cannot work if the server or network fails, so the network must be reliable.
- Thick clients would cost more and need individual updates, which is unnecessary for these tasks; so thin clients are the better choice.
- If the server fails, the clients lose access to its services and data (single point of failure).
- Servers are expensive and need a specialist network manager / the server can become a bottleneck when many clients make requests at once.
6 multiple-choice questions on this lesson
From the topic question bank. Assign them in the app for a marked score in your gradebook, or run the topic as a class game.
Which statement describes a WAN rather than a LAN?
- AIt covers a large geographical area and uses infrastructure such as telephone lines leased from other companies
- BIt covers a single site and all its cabling is owned by the organisation that uses it
- CIt must use the peer-to-peer model because there is no room for a central server
- DIt connects devices only by wireless links, so no cables are needed at all
Which statement about the peer-to-peer model is correct?
- AEach computer can act as both a client and a server, and there is no central server
- BOne powerful computer stores all the files and answers every request
- CEach computer depends on a server for its processing and storage
- DEvery computer must be connected directly to every other computer by a cable
Which situation is best suited to a client-server network?
- AA college of 600 students who must log on from any computer and whose files are backed up centrally each night
- BTwo friends who occasionally copy music files between their laptops at home
- CA family of four who share one printer attached to the living room computer
- DThree colleagues who swap large video clips with each other on a short project
A school replaces old desktop PCs with cheap terminals that have very little storage and a low-power processor. Programs run, and files are stored, on a central server. What are the terminals?
- AThin clients
- BThick clients
- CPeers
- DRouters
An office runs a peer-to-peer network. Which problem is most likely to occur that a client-server network would avoid?
- AA shared file cannot be opened because the colleague whose computer holds it has switched it off
- BEvery request fails if the single central computer breaks down
- CUsers cannot share a printer unless it is connected to a dedicated print server
- DThe network costs more because a server licence and a network manager are needed
Engineers visit remote sites where the network connection is slow and often drops. Their design software must keep working during these drops. Which choice is best, and why?
- AThick clients, because the software runs and processes data locally and does not depend on the server for every task
- BThin clients, because the server does all the processing, so a slow connection does not matter
- CThin clients, because they have no local storage that could be lost during a drop
- DThick clients, because they send every keystroke to the server so no work is lost
Quiz key
A WAN spans a large geographical area (towns, countries) and relies on infrastructure such as telephone lines, fibre links and satellites that is leased from telecoms providers. A single site with cabling owned by the organisation is the definition of a LAN. Either kind of network can use client-server or peer-to-peer, and either can mix wired and wireless links.
In peer-to-peer every peer can both request and supply resources, and no central server exists. A single computer that stores the files and answers requests is the server in a client-server network. Depending on a server for processing and storage describes a thin client. Peer-to-peer is a model of who does what, not a topology, so the peers need not be cabled directly to each other.
Hundreds of users, log-on from any machine and central nightly backups all call for a server that holds user accounts and files in one managed place. The other three are small groups with occasional, informal sharing: a peer-to-peer arrangement is cheaper and simpler there and needs no dedicated server or network manager.
A thin client relies on the server for processing and storage, which is exactly what these terminals do. A thick client does most of its own processing and holds its own software. A peer would share its own resources as a server too, which these terminals cannot. A router connects networks and forwards packets; it is not a user's terminal.
In peer-to-peer, files stay on the individual peers, so a file is unavailable whenever its owner's computer is off; backup and security are also left to each user. A single point of failure at a central computer is a weakness of client-server, not peer-to-peer. Peers can share a printer attached to any one of them without a print server. Extra cost for a server and a manager is a drawback of client-server, not something it avoids.
A thick client does most of its own processing and storage, so the engineers can carry on when the connection drops and synchronise later. A thin client depends on the server for processing, so a slow or broken connection stops it working, which rules out both thin-client answers. Sending every keystroke to the server describes a thin client's dependence, not a thick client's benefit.
Slides for this lesson
A projectable deck for every pack is on the way. Until then, present the student lesson full screen: its sections, figure and lab tabs follow the same order as the plan above.