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This lesson brings together all the topics from OCR J277 Section 1.3 (Computer Networks) and provides exam-style questions with model answers. Use this to consolidate your knowledge and practise the skills needed for Paper 1.
| Topic | Key Points |
|---|---|
| LAN vs WAN | LAN: small area, single owner; WAN: large area, third-party infrastructure |
| Client-server vs P2P | Client-server: central server; P2P: all devices are equal |
| Topologies | Star (central switch), mesh (multiple paths), bus (shared backbone) |
| Network hardware | NIC (MAC address), switch (LAN, MAC), router (between networks, IP), WAP (wireless) |
| Internet, DNS, hosting | DNS resolves domain names to IPs; hosting stores websites on servers |
| Protocols | TCP/IP, HTTP/S, FTP, SMTP, IMAP |
| TCP/IP layers | Application, Transport, Internet, Network Interface |
| Packet switching | Data split into packets, different routes, reassembled at destination |
| Wired vs wireless | Ethernet/fibre (fast, reliable) vs WiFi/Bluetooth (mobile, convenient) |
Question: Explain the difference between a LAN and a WAN.
Model Answer:
A LAN (Local Area Network) covers a small geographical area such as a single building or school campus, and is owned and managed by one organisation. [1 mark]
A WAN (Wide Area Network) covers a large geographical area such as multiple cities or countries, and typically uses infrastructure owned by third-party telecommunications companies. [1 mark]
The internet is the largest example of a WAN, connecting millions of LANs worldwide. [1 mark]
Question: Compare star and bus network topologies, explaining one advantage and one disadvantage of each.
Model Answer:
Star topology:
Bus topology:
Question: Describe the purpose of each of the following network devices: (a) Switch (b) Router
Model Answer:
(a) Switch: A switch connects devices within a LAN and directs data to the specific device it is intended for. It does this by reading the MAC address in the data frame and forwarding it only to the port connected to that device. This is more efficient than a hub, which broadcasts data to all devices. [2 marks]
(b) Router: A router connects different networks together (e.g. a LAN to the internet/WAN). It reads the IP address in each data packet and determines the best route to forward the packet to the destination network. Routers also perform NAT (Network Address Translation) to translate between private and public IP addresses. [2 marks]
Question: State the protocol used for each of the following tasks: (a) Sending an email (b) Retrieving an email from a mail server (c) Securely browsing a website
Model Answer:
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