The shape of the lesson
By the end of the lesson, learners can
- Internet or web?: In the lab, send a message across a network of routers.
- Internet hardware: The syllabus names four things that connect homes, businesses and mobile users to the internet.
- Bit streaming: Streaming lets you start watching before the whole file has arrived.
- Internet: the network of networks (infrastructure). WWW: linked web pages, a service over it.
- Hardware: modem, PSTN, dedicated line, cell phone network: say what each does.
- Streaming: played from a buffer as it arrives; real-time (live) or on-demand (stored).
- Calculations: bits = bit rate × seconds; divide by 8 for bytes.
One picture every idea returns to
The internet is the global network of interconnected networks: the physical infrastructure of cables, routers and links. The World Wide Web is a collection of web pages and resources, linked by hyperlinks and reached using HTTP(S) and a browser; it is just one service that runs over the internet. The internet is supported by modems, the PSTN, dedicated lines and the cell phone network. Bit streaming sends audio or video as a continuous stream of bits that is played as it arrives, from a buffer, either real-time (live) or on-demand (pre-recorded); the connection's bit rate must be at least the stream's bit rate.
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, Roads and traffic.. People use the words internet and web as if they meant the same thing. 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: Internet or web? | In the lab, send a message across a network of routers. Project tab 1 of the lab (Packets crossing the internet) and let a student drive it while the class predicts. | Whole class, then pairs |
| 13 to 21 min | Teach and check: Internet hardware | The syllabus names four things that connect homes, businesses and mobile users to the internet. | Pairs |
| 21 to 30 min | Teach and check: Bit streaming | Streaming lets you start watching before the whole file has arrived. Model the worked example Data used by a stream on the board, one line at a time. Your turn: A song is streamed at 320 kbps (320 000 bits per second) and lasts 4 minutes. How many megabytes (1 MB = 1 000 000 bytes) are transferred? | Anticipation / Reaction Guide |
| 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, 20 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 Bit streaming, 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.
Anticipation / Reaction Guide
Before the lesson, students mark five statements true or false. After the teaching they mark them again and justify any change of mind in one sentence each. The statements come from the examiner traps below.
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 |
|---|---|
| "The internet is the web" and "you use a browser to get on the internet" both lose marks. | Email, for example, uses the internet but not the web. |
| Watch the units: bit rates are in bits per second (lower-case b), file sizes usually in bytes (upper-case B). | Divide by 8 to convert bits to bytes. |
The internet and the world wide web: worksheet
6 questions, 20 marks. Written in the style of the papers; no past paper question is reproduced.
Explain the difference between the internet and the World Wide Web.
Describe the role of each of the following in supporting the internet: (a) modem (b) PSTN (c) dedicated line (d) cell phone network.
Explain the difference between real-time and on-demand bit streaming, giving an example of each.
A lesson recording is streamed at 2.5 Mbps and lasts 30 minutes. Calculate the amount of data transferred in megabytes. Use 1 Mbps = 1 000 000 bits per second and 1 MB = 1 000 000 bytes. Show your working.
Explain the purpose of a buffer when streaming video.
A household has a 25 Mbps connection. A 4K video stream needs 15 Mbps and an HD stream needs 5 Mbps. One person watches 4K while two others each watch HD. Will all three play smoothly? Explain.
Answer key and marking notes
- The internet is a global network of interconnected networks / the infrastructure (cables, routers).
- The WWW is a collection of web pages and resources linked by hyperlinks, accessed using HTTP(S) and a browser.
- The WWW is one service that runs over the internet (others include email and file transfer).
- (a) Converts digital signals to analogue for transmission over a telephone line, and analogue back to digital.
- (b) The public telephone network of lines and exchanges, which also carries internet data (dial-up/broadband).
- (c) A permanent, private (leased) connection between two points with guaranteed bandwidth.
- (d) Gives mobile devices internet access by radio through base stations / masts in each cell.
- Real-time: the event is encoded and streamed live as it happens.
- Example: a live sports match / a video call.
- On-demand: a pre-recorded file is stored on a server and streamed when the user requests it; the user can pause, rewind and skip.
- Example: a film from a streaming library / a podcast.
- 30 minutes = 1800 seconds.
- 2 500 000 × 1800 = 4 500 000 000 bits.
- ÷ 8 = 562 500 000 bytes = 562.5 MB.
- Data received is stored temporarily in the buffer (memory) before it is played.
- Playback is taken from the buffer, so short drops in the connection speed do not interrupt the video.
- Playback only pauses if the buffer empties because data arrives more slowly than it is played.
- Total bit rate needed: 15 + 5 + 5 = 25 Mbps.
- This equals the full 25 Mbps available, with no spare capacity for other traffic or drops in speed.
- So the streams are likely to buffer at times (or the services will reduce quality); they may only just play smoothly.
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 correctly distinguishes the internet from the World Wide Web?
- AThe internet is a global network of interconnected networks; the WWW is a collection of linked web pages accessed over it
- BThe WWW is a global network of cables and routers; the internet is the collection of web pages it carries
- CThe internet and the WWW are the same thing, but the WWW is the newer name
- DThe internet is used only for email; the WWW is used for everything else
Which activity uses the internet but does not use the World Wide Web?
- ASending a message with a phone's dedicated email app
- BReading a news article on a website in a browser
- CSearching for a recipe on a search engine's web page
- DFilling in an online order form on a shop's website
What is the purpose of a modem?
- ATo convert digital signals to analogue for sending over a telephone line, and analogue back to digital on receipt
- BTo translate domain names into the IP addresses of web servers
- CTo give each device on a home network its own private IP address
- DTo provide a permanent private connection between two business sites
A video is streamed at 3 Mbps (3 000 000 bits per second) for 40 minutes. How much data is transferred? (1 MB = 1 000 000 bytes.)
- A900 MB
- B7200 MB
- C15 MB
- D112.5 MB
A household's broadband connection has a bit rate of 25 Mbps. Each high-definition stream needs 6 Mbps. What is the largest number of streams that can play at the same time without buffering?
- A4
- B5
- C3
- D6
Why does a real-time (live) stream normally keep a much smaller buffer than an on-demand stream of a film?
- AA large buffer would make viewers fall further behind the live event, and the future data does not exist yet anyway
- BLive streams are not compressed, so they would fill a large buffer too quickly
- COn-demand streams are downloaded completely before playback starts, so they need more memory
- DA live stream is sent over a dedicated line, so the data never arrives late
Quiz key
The internet is the physical network of networks (cables, routers, links) using TCP/IP; the WWW is the collection of linked web pages reached using HTTP(S) and a browser, one of many services running over the internet. The second option swaps the two. They are not the same thing. The internet carries many services, including the web, email, VoIP and streaming.
A dedicated email app sends messages with email protocols over the internet without requesting any web pages. Reading a news site, using a search engine's page and filling in a shop's web form all fetch web pages using HTTP(S), so all three use the WWW.
A modem modulates digital data into an analogue signal for the telephone line and demodulates incoming analogue signals back to digital. Translating domain names is the DNS. Allocating private IP addresses is DHCP, usually in the router. A permanent private link between two sites is a dedicated (leased) line.
40 minutes = 2400 s. Bits = 3 000 000 × 2400 = 7 200 000 000; bytes = 7 200 000 000 ÷ 8 = 900 000 000 = 900 MB. 7200 MB forgets to divide by 8 (it is megabits). 15 MB uses 40 instead of 2400 seconds. 112.5 MB divides by 8 twice.
4 streams need 4 × 6 = 24 Mbps, which fits within 25 Mbps; 5 streams would need 30 Mbps, more than the connection supplies, so their buffers would empty. 5 comes from rounding 25 ÷ 6 = 4.17 up instead of down. 3 streams would play, but it is not the largest number. 6 confuses the bit rate of one stream with the number of streams.
Data for a live event is produced as it happens, so it cannot be buffered far ahead, and a big buffer only adds delay behind the live action. Live streams are compressed just like on-demand ones. On-demand streaming plays as data arrives; it is not a full download first, though it can build a larger buffer. Live streams travel over the ordinary internet and can suffer delays like any other data.
What to project
The student lesson embeds these tabs. Open them full screen on the projector; every slider has a drag handle on the stage.
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.