Spec & Goals 3 min
AQA Spec 3.5 · Fundamentals of computer networks (whole unit)
By the end of this lesson you can:
- Revise and self-check the whole of Unit 5, spotting your weak topics.
- Answer exam questions that span all of spec 3.5, for the marks on offer.
- Make a focused revision plan that targets the topics you got wrong.
Warm-Up — command words & the paper 5 min
This is the last lesson of Unit 5. First, know the exam you are sitting.
Command words tell you what to do
Read the command word first — it sets how much to write.
| Command word | What it demands |
|---|---|
| State / Identify | A word or short phrase. No explanation. |
| Describe | Say what something is, or the steps, with detail. |
| Explain | Give reasons — the how or the why. |
| Compare / Discuss | Both sides / trade-offs; an extended answer. |
Key Concept — your Unit 5 spec checklist 14 min
Tick each spec point. If you cannot do one, that is a topic to revise tonight.
| Spec point | You should be able to… |
|---|---|
| Network types | Define a network; give advantages/disadvantages; describe PAN, LAN and WAN. |
| Wired vs wireless | Compare them; give advantages/disadvantages of wireless; list factors affecting performance. |
| Topologies | Draw and compare the star and bus topologies. |
| Hardware | State the role of the NIC, switch, router and WAP; know the transmission media. |
| Internet, DNS, cloud | Define the internet; describe a DNS lookup; define hosting and the cloud. |
| Protocols | Define a protocol; state the purpose of TCP, IP, HTTP, HTTPS, FTP, SMTP, IMAP. |
| Layers | Name the 4 TCP/IP layers in order and the protocols in each. |
| Packet switching | Describe a packet and how packet switching works. |
| Encryption | Define encryption; explain how it secures data in transit. |
The two topologies at a glance
Worked Example — a full multi-part question 12 min
Here is one question with three parts. We earn the marks aloud.
Part (a) — Describe the difference between a LAN and a WAN. [2 marks]
A LAN covers a single small site, with hardware the organisation owns (1). A WAN covers a large geographic area and uses third-party infrastructure (1).
Part (b) — A user types a web address. Describe how the DNS is used. [3 marks]
The browser sends the domain name to a DNS server (1); the DNS server returns the matching IP address (1); the browser uses the IP address to request the page from the web server (1).
Part (c) — Describe how packet switching sends the page back. [3 marks]
The data is split into packets (1); packets travel independently and may take different routes (1); they are reassembled in order at the destination using the packet numbers (1).
Try It Yourself — timed mini-paper 12 min
Give yourself 12 minutes. Write full answers; check them with your teacher.
State what the abbreviations LAN and WAN stand for. [2 marks]
Describe the difference between a switch and a router. [2 marks]
State the four layers of the TCP/IP model in order. [4 marks]
Explain how encryption keeps data safe on a wireless network. [3 marks]
Compare the star and bus topologies in terms of cost and reliability. [4 marks]
📝 Exam Practice 10 min
These questions span the whole of Unit 5. Match your answer to the command word and the marks.
Identify the protocol used to (a) send email and (b) securely transfer a web page.
Mark scheme
- (a) SMTP (1).
- (b) HTTPS (1).
Describe how devices are connected in a bus topology.
Mark scheme
- All devices share/connect to a single backbone cable (1).
- With a terminator at each end (accept: data sent both ways along the cable) (1).
Explain why a layered model (e.g. TCP/IP) is used for networking.
Mark scheme
- Each layer can be developed/changed independently (1).
- Without affecting the others / it breaks a complex task into parts / aids standardisation (1).
Describe how packet switching is used to send data across the internet.
Mark scheme
- Data is split into packets (1).
- Packets travel independently, possibly by different routes (1).
- They are reassembled in order at the destination using packet numbers (1).
A small business is choosing between a wired and a wireless office network. Discuss the advantages and disadvantages of each.
Mark scheme
Up to 4 marks for balanced points, e.g.:
- Wired — faster / more reliable / more secure (1); but costly to cable / not portable (1).
- Wireless — portable / cheaper to install / easy to add devices (1); but slower / interference / less secure (1).
Recap & Key Terms 3 min
Use your mini-paper marks to plan tonight's revision.
- Muddled the network types? Redo CS-L5-01 (PAN/LAN/WAN).
- Unsure on wired vs wireless or performance? Redo CS-L5-02.
- Tripped on topologies? Redo CS-L5-03 — star vs bus.
- Confused the hardware? Redo CS-L5-04 — switch vs router vs WAP.
- Shaky on DNS or the cloud? Redo CS-L5-05.
- Lost marks on protocols? Redo CS-L5-06 — especially SMTP vs IMAP.
- Mixed up the layers? Redo CS-L5-07 — A-T-I-L.
- Unsure on packets? Redo CS-L5-08.
- Vague on encryption? Redo CS-L5-09.
- LAN / WAN
- LAN — one site, hardware you own; WAN — a large area using third-party infrastructure.
- Topology
- The layout of a network — AQA examines star and bus.
- Switch / router
- A switch links devices on one LAN (by MAC); a router links different networks (by IP).
- DNS
- Translates a domain name into its IP address.
- Protocol
- A set of rules governing how devices communicate.
- TCP / IP
- TCP splits/reassembles data into packets; IP addresses and routes them.
- TCP/IP layers
- Application, Transport, Internet, Link.
- Packet switching
- Sending data as packets that travel independently and are reassembled at the destination.
- Encryption
- Scrambling data with a key so it cannot be read if intercepted.
Homework 1 min
Task (≤ 15 min): Revisit your weakest topic from the mini-paper. Open that lesson and redo its Exam Practice section.
Bring one question you still find hard to the next session, so we can work through it together.