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GCSE AQA Computer Science (8525): 3.5 Fundamentals of Computer Networks Exam

Answers and Detailed Explanations

Section A: Short-Answer Questions

  1. Computer Network (1 mark):
    A group of interconnected computers and devices that can communicate and share resources. [1 mark]

    Alternate acceptable answer: A computer network is formed when two ore more computers/devices are connected to communicate and share resources. [1 mark]
    Explanation: Enables data sharing, printing, internet access.

  2. LAN vs WAN (2 marks):
    LAN: Local Area Network – covers a small geographical area (e.g., one building, one home, one school). [1 mark]
    WAN: Wide Area Network – covers a large area (e.g., cities, countries, Microsoft/Google/Facebook in UK, US, and various other geographical locations). [1 mark]
    Explanation: LAN = Home/School/Small Office; WAN = internet, bank branches.

  3. Network Topologies (2 marks):
    Any two: Star, Bus, Ring, Mesh. [1 mark each]
    Explanation: Describes physical/logical layout of devices.

  4. Protocol (2 marks):
    A set of rules that devices follow to communicate. [1 mark]
    Example: HTTP, TCP, IP, FTP, DNS. [1 mark]
    Explanation: Ensures reliable data transfer.

  5. Switch Function (1 mark):
    Forwards data only to the intended device using MAC addresses. [1 mark]
    Explanation: Reduces network congestion vs. hub.

  6. Router Function (1 mark):
    Connects different networks and directs data packets using IP addresses. [1 mark]
    Explanation: Enables internet access, connects LAN to WAN.

  7. TCP/IP Layers (1 mark):
    Application, Transport, Internet, Link (or Network Access). [1 mark]
    Explanation: Simplified 4-layer model for internet communication.

Section B: Explanation and Application Questions

  1. Star vs Bus Topology (4 marks):
    Star: All devices connect to a central switch/hub.

    • Advantage: If one device fails, others unaffected. [1 mark]
    • Disadvantage: Central point failure stops whole network. [1 mark]
      Bus: Devices connected to a single backbone cable.
    • Advantage: Cheap and easy to install. [1 mark]
    • Disadvantage: Cable break affects all devices. [1 mark]
      Explanation: Star is more reliable and common in modern networks.

  2. Application & Transport Layers (3 marks):
    Application Layer: Provides network services to user applications (e.g., HTTP for web, SMTP for email). [1.5 marks]
    Transport Layer: Manages end-to-end communication, ensures reliable data delivery (e.g., TCP for reliability, UDP for speed). [1.5 marks]
    Explanation: Application = user interface; Transport = data delivery control.

  3. Packet Switching (3 marks):
    Data is broken into small packets. [1 mark]
    Each packet has a header with source/destination IP, sequence number. [1 mark]
    Packets travel independently, reassembled at destination. [1 mark]
    Explanation: Efficient, allows multiple paths, used in the internet.

  4. LAN or WAN? (2 marks):
    WAN [1 mark]
    Justification: 2 km apart exceeds typical LAN range (100m–1km); requires ISP or leased lines. [1 mark]
    Explanation: LAN is limited to one site; WAN connects distant locations.

  5. TCP/IP vs OSI Model (3 marks):
    TCP/IP has 4 layers; OSI has 7 layers. [1 mark]
    TCP/IP: Practical model used in real networks (internet). [1 mark]
    OSI: Theoretical reference model for teaching (Application, Presentation, Session, Transport, Network, Data Link, Physical). [1 mark]
    Explanation: TCP/IP is simpler and implemented; OSI is more detailed.

Total Marks: 25