CS29: Network Types & Topologies

📋 What is a Computer Network?

Before networks, computers worked in isolation (standalone). Each computer had its own printer, its own storage, and no way to share data with other computers. Networks allow computers to communicate and share resources efficiently.

• Networks allow sharing of files, printers, and internet connections
• Users can communicate via email, messaging, and video calls
• Centralised data storage makes backups easier
• Software can be shared and updated centrally

🌐 Types of Networks

PAN (Personal Area Network)

• Very small range (usually under 10 metres)
• Connects personal devices together
• Typically uses Bluetooth or USB
• Examples: connecting wireless headphones to a phone, a smartwatch to a phone

LAN (Local Area Network)

• Small geographical area (one building or site)
• Usually owned and maintained by the organisation
• Typically uses Ethernet (wired) or Wi-Fi (wireless)
• High data transfer rates
• Lower cost to set up and maintain
• Examples: school network, home network, office network

WAN (Wide Area Network)

• Large geographical area (cities, countries, continents)
• Uses third-party telecommunications infrastructure (phone lines, satellites)
• Typically uses fibre optic or satellite connections
• Lower data transfer rates than LANs (generally)
• Higher cost and more complex to maintain
• The internet is the largest WAN in the world

🔌 Wired vs Wireless Connections

Wired Connections

Ethernet

• Uses copper cables (Cat5e, Cat6) to transmit data as electrical signals
• Very reliable and secure (physical cable required to intercept)
• Speeds up to 10 Gbps
• Not affected by interference or signal blocking
• Devices must be physically connected - limits mobility

Fibre Optic

• Uses glass or plastic fibres to transmit data as pulses of light
• Extremely fast (up to 100 Gbps+)
• Can transmit over very long distances without signal loss
• Not affected by electromagnetic interference
• Very expensive to install
• Used for backbone connections and WAN links

Wireless Connections

Wi-Fi

• Uses radio waves to transmit data through the air
• Convenient - no cables needed, devices can move freely
Speeds up to several Gbps (Wi-Fi 6)
• Signal can be blocked by walls and interference
• Less secure - signals can be intercepted
• Range typically 30-100 metres indoors

Bluetooth

• Uses short-range radio waves (typically under 10 metres)
• Low power consumption - designed for battery-powered devices
• Relatively slow data transfer rate
• Used for connecting personal devices (headphones, keyboards, speakers)

⚖️ Advantages and Disadvantages of Networking

🔷 Network Topologies

Star Topology

In a star topology, all devices connect to a central hub or switch. All communication goes through this central device.

• Advantages:
• If one cable fails, only that device is affected
• Easy to add new devices without disrupting the network
• Central hub makes it easy to manage and monitor
• High performance - each device has its own dedicated connection
• Disadvantages:
• If the central hub/switch fails, the entire network goes down
• Requires more cabling than some other topologies
• The central device is a single point of failure

Mesh Topology

In a mesh topology, devices are interconnected with multiple connections. In a full mesh, every device is connected to every other device. In a partial mesh, some devices have multiple connections.

• Advantages:
• No single point of failure - data can be routed around failed connections
• Highly reliable and fault-tolerant
• Data can take multiple paths to its destination
• Disadvantages:
• Very expensive (lots of cabling/connections needed)
• Complex to set up and manage
• Full mesh is impractical for large networks (n(n-1)/2 connections)

⚠️ Common Mistakes to Avoid

❓ Practice Questions

✅ Answers

1. PAN: Personal Area Network, very small range (under 10m), connects personal devices like phone to headphones. LAN: Local Area Network, covers a single building/site, e.g. a school network. WAN: Wide Area Network, covers large geographical area, e.g. the internet.
2. Ethernet advantages: faster and more reliable, more secure (physical cable needed). Ethernet disadvantages: limited mobility, requires cabling to each device. Wi-Fi advantages: no cables needed, devices can move freely. Wi-Fi disadvantages: less secure (signals can be intercepted), signal can be blocked or interfered with.
3. Advantages: resource sharing (printers), file sharing between users, centralised backups. Disadvantages: security risks (malware spreads), cost of setup and maintenance, if server fails many users affected.
4. Star: all devices connect to a central hub/switch. Main advantage: easy to add devices, one cable failure only affects one device. Mesh: devices have multiple interconnections. Main advantage: no single point of failure - highly reliable because data can route around failed connections.
5. Fibre optic uses light signals through glass fibres, giving much higher speeds, ability to transmit over much longer distances without signal loss, and immunity to electromagnetic interference. Copper Ethernet is limited by distance and is affected by interference.

🎯 Exam Tips

• Know the three network types and their ranges
• For wired vs wireless, always compare security, speed, cost, and mobility
• Give balanced advantages AND disadvantages of networking
• Star topology: central hub is the single point of failure
• Mesh topology: no single point of failure is the key advantage
• The internet is a WAN, not a LAN

⚠️ Common Errors

✍️ Model Answer

📊 AO Deep Dive

📝 Exam Technique

📝 Exam Questions by Topic

• AQA Past Papers - Topic Questions -- AQA
• Edexcel Past Papers - Topic Questions -- Edexcel
• OCR Past Papers - Topic Questions -- OCR
• Eduqas Past Papers - Topic Questions -- Eduqas

🎬 Video Resources

• BBC Bitesize: GCSE Computer Science
• YouTube: GCSE Computer Science Network Types Topologies LAN WAN Star Mesh