Networks Exam Practice

This lesson brings together everything you have learned about networks in this course. It provides guidance on tackling exam questions, common question types, key definitions you must know, and worked examples with model answers.

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Key Definitions to Memorise

The following definitions are commonly tested in GCSE Computer Science exams. Learn them precisely.

Term	Definition
LAN	A network covering a small geographical area (e.g. a building), owned and maintained by the organisation
WAN	A network covering a large geographical area, using third-party infrastructure
PAN	A very small network around an individual person, typically using Bluetooth
Protocol	A set of rules that governs how data is transmitted across a network
IP address	A unique numerical address assigned to every device on a network
MAC address	A unique hardware address permanently assigned to a network interface card
DNS	A system that translates domain names into IP addresses
Packet	A small unit of data sent across a network, containing a header, payload and trailer
Firewall	A security system that monitors and controls network traffic based on rules
Encryption	Converting data into an unreadable format to prevent unauthorised access
Malware	Malicious software designed to harm, exploit or gain unauthorised access to a system
Phishing	A social engineering attack using fake emails/messages to trick users into revealing personal information
SQL injection	An attack that inserts malicious SQL code into a website's input field to manipulate its database
DDoS	An attack that overwhelms a server with traffic from many sources, preventing legitimate access

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Common Question Types

Type 1: Compare Two Things (2-4 marks)

Questions asking you to compare LAN vs WAN, wired vs wireless, star vs mesh, TCP vs UDP, etc.

Strategy:

• Make distinct points — do not repeat the same point in different words.
• Use a table format or clearly label each comparison point.
• Cover at least the number of marks available (e.g. 4-mark question = 4 comparison points).

Example Question: Compare a LAN with a WAN. (4 marks)

Model Answer:

1. A LAN covers a small geographical area such as a single building, whereas a WAN covers a large area such as a country or the world.
2. A LAN is owned and maintained by the organisation using it, whereas a WAN uses infrastructure owned by third parties such as telecom companies.
3. A LAN typically provides higher data transfer speeds than a WAN.
4. A LAN has lower ongoing costs since the organisation owns the equipment, whereas a WAN has higher costs due to leased lines and third-party charges.

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Type 2: Describe a Process (4-6 marks)

Questions asking you to describe how DNS works, how data is transmitted using packet switching, how an email is sent, etc.

Strategy:

• Write in numbered steps or clear sequential paragraphs.
• Be specific — use technical terms such as "packet", "IP address", "routing table", "sequence number".
• Check you have covered the full process from start to finish.

Example Question: Describe how packet switching is used to transmit data across the internet. (6 marks)

Model Answer:

1. The data is broken down into smaller units called packets. Each packet is given a header containing the source IP address, destination IP address and a sequence number.
2. Each packet is sent to the nearest router. The router reads the destination IP address and consults its routing table to determine the best path for the packet.
3. The packet is forwarded to the next router, and this process is repeated at each router along the route.
4. Different packets may take different routes across the internet depending on network congestion and available links.
5. As a result, packets may arrive at the destination out of order. The receiving device uses the sequence numbers to reassemble the packets in the correct order.
6. If any packets are missing or corrupted (detected by the checksum in the trailer), the receiving device requests retransmission of those packets from the sender.

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Type 3: Explain a Threat and How to Prevent It (3-6 marks)

Questions about phishing, malware, SQL injection, DDoS, etc.

Strategy:

• Define the threat.
• Explain how it works (the mechanism of the attack).
• State the impact (what damage it causes).
• Suggest prevention measures with brief explanations.

Example Question: Explain what a phishing attack is and describe two ways an organisation can protect against it. (4 marks)

Model Answer: Phishing is a social engineering attack where an attacker sends fake emails or messages that appear to come from a trusted source. The message contains a link to a fake website designed to trick the user into entering personal information such as login credentials or bank details (2 marks for description).

Prevention 1: Staff training — educating employees to recognise suspicious emails, check sender addresses carefully and avoid clicking unknown links (1 mark).

Prevention 2: Email filtering software that scans incoming messages for known phishing indicators and blocks or flags suspicious emails (1 mark).

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Type 4: Recommend a Solution (3-6 marks)

Scenario-based questions asking you to advise on network setup, topology choice, security measures, etc.

Strategy:

• Read the scenario carefully — identify the specific requirements.
• Make a clear recommendation and then justify it with reasons linked to the scenario.
• Consider both advantages and any trade-offs.

Example Question: A small business has 15 computers in a single office. The owner wants to set up a network. Recommend a suitable network topology and justify your choice. (4 marks)

Model Answer: I would recommend a star topology. In a star topology, each computer is connected to a central switch (1 mark).

If one computer or cable fails, only that device is affected and the rest of the network continues to work, which is important for business continuity (1 mark).

A star topology is easy to add new devices to — the business can simply connect a new computer to a spare port on the switch as the business grows (1 mark).

The central switch makes it easier to manage and monitor the network, and performance is good because a switch directs data only to the intended device, avoiding collisions (1 mark).

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Common Mistakes to Avoid

Mistake	Correction
Confusing the internet with the World Wide Web	The internet is the infrastructure; the WWW is a service running on it
Confusing a switch with a router	A switch connects devices within a LAN using MAC addresses; a router connects different networks using IP addresses
Confusing MAC address with IP address	A MAC address is a permanent hardware identifier; an IP address is a logical address that can change
Saying encryption "stops hackers"	Encryption makes data unreadable if intercepted — it does not prevent interception, just makes the data useless to the attacker
Vague answers about security	Always name specific measures and explain how they work
Describing only one side of a comparison	Ensure you cover both items being compared

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Quick Revision Checklist

Use this checklist to ensure you have revised all the key topics:

• Types of network: LAN, WAN, PAN
• Client-server vs peer-to-peer networks
• Network topologies: star, bus, mesh, ring
• Network hardware: NIC, switch, router, WAP
• The internet and DNS (step-by-step lookup process)
• IP addresses: IPv4 vs IPv6
• Protocols: TCP/IP, HTTP/HTTPS, FTP, SMTP, IMAP
• TCP/IP model: 4 layers
• Packet switching: how packets are routed and reassembled
• Wired vs wireless connections
• Wi-Fi standards and frequency bands
• Security threats: malware types, phishing, SQL injection, DDoS, brute force
• Security measures: firewalls, encryption, authentication, MAC address filtering
• Defence in depth (layered security approach)

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Final Tips

1. Use technical vocabulary — examiners reward precise use of terms like "packet", "routing table", "MAC address", "encryption", "protocol".
2. Answer in context — relate your answer to the specific scenario given in the question.
3. Show your understanding — do not just list facts; explain how and why things work.
4. Manage your time — do not spend too long on low-mark questions; save time for the longer ones.
5. Read the question carefully — note command words like "describe", "explain", "compare", "evaluate" and "recommend" — they each require different types of response.