Networks

This topic explores fundamental concepts that shape our understanding of the world.

Computer networks enable communication between devices. A-Level covers the principles of how data is transmitted, routed, and secured across local and wide-area networks, as well as the protocols and models that govern these processes.

• LAN, WAN, WLAN — classification by geography and technology
• Client-server vs. peer-to-peer — architecture models and their trade-offs
• Topologies — star, bus, ring, mesh, hybrid; advantages and disadvantages of each
• Transmission media — copper (twisted pair, coaxial), fibre optic, wireless; bandwidth and latency trade-offs

• OSI 7-layer model — Physical, Data Link, Network, Transport, Session, Presentation, Application
• TCP/IP 4-layer model — Link, Internet, Transport, Application
• Protocol mapping — where HTTP, TCP, IP, Ethernet sit in each model
• Encapsulation — how data is wrapped with headers at each layer

• TCP — reliable, connection-oriented; three-way handshake, flow control
• UDP — unreliable, connectionless; when speed matters more than reliability
• IP addressing — IPv4 (dotted decimal), subnet masks, CIDR notation
• HTTP/HTTPS — request-response model, status codes, TLS encryption
• DNS — domain name resolution, hierarchical lookup
• DHCP — automatic IP address assignment

• Firewalls — packet filtering, stateful inspection
• Encryption — symmetric vs. asymmetric; TLS/SSL handshake
• Authentication — passwords, biometrics, multi-factor authentication
• Malware and attacks — viruses, worms, trojans, phishing, DDoS, SQL injection

• HTML, CSS, JavaScript — structure, presentation, behaviour
• Client-side vs. server-side processing — where computation happens and why

1. Draw the OSI and TCP/IP models side by side. Memorise which protocols operate at which layer.
2. Trace a packet from application layer through to physical. Describe what headers are added at each layer (encapsulation).
3. Compare TCP and UDP with specific use cases. E.g., TCP for web browsing, UDP for video streaming.
4. Practise IP subnetting. Calculating network address, broadcast address, and host range from an IP and subnet mask.
5. Link security concepts to real-world scenarios. Exam questions often describe a situation and ask which protection to apply.

Start with network fundamentals and the OSI model, then move to protocols and security. Each page provides definitions, diagrams, worked examples, and exam-style problems.

This section provides comprehensive A-Level Computer Science content for Networks, covering all specification points with detailed explanations, worked examples, and practice questions.

Each page in this section includes:

• Definitions: Clear, precise explanations of key concepts
• Worked Examples: Step-by-step solutions with annotations
• Practice Questions: Multiple-choice and structured questions with mark schemes
• Common Pitfalls: Errors to avoid and how to fix them
• Exam Tips: Strategies for maximising marks in this topic

1. Read the introductory page to understand the topic overview
2. Work through each sub-topic in order
3. Attempt the practice questions before checking solutions
4. Use the flashcards to revise key terminology
5. Complete the diagnostic test to identify remaining gaps

• Core definitions and principles
• Application to examination-style questions
• Links to related topics across the specification
• Assessment objective alignment (AO1, AO2, AO3)

• Active Recall: Test yourself regularly rather than re-reading notes
• Spaced Practice: Revisit this topic at increasing intervals
• Interleaving: Mix with other topics during revision sessions
• Elaboration: Explain concepts in your own words

Focus on command word interpretation and mark scheme analysis. Practice timing yourself on questions to build speed and accuracy. Review examiner reports for this topic to understand common student errors.

This landing page provides comprehensive coverage of Computer Science content for the Alevel qualification, with detailed explanations, worked examples, and practice questions aligned to the specification.

This page includes:

• Key Definitions: Precise explanations of essential concepts
• Core Concepts: Detailed treatment of fundamental principles
• Worked Examples: Step-by-step solutions demonstrating application
• Practice Questions: Examination-style questions with mark schemes
• Common Pitfalls: Frequent errors and how to avoid them
• Exam Tips: Strategies for maximising marks

1. Read through the introductory material to establish context
2. Study the definitions and core concepts carefully
3. Work through the worked examples, following each step
4. Attempt the practice questions independently
5. Review your answers against the provided solutions
6. Note any areas requiring further revision

• Foundational definitions and terminology
• Application of principles to examination contexts
• Connections to related topics within the specification
• Assessment objective alignment

• Active Recall: Test yourself on the material rather than passively re-reading
• Spaced Repetition: Review this content at increasing intervals
• Interleaving: Mix this topic with others during study sessions
• Elaborative Interrogation: Ask yourself why each concept works

Practise applying these concepts under timed conditions. Focus on understanding what each question is asking and how marks are allocated. Review examiner reports to learn from common mistakes made by other students.

• Computer Science
• Network Fundamentals
• Network Security