📡 Component 1 · 1.3 Computer Networks
1.3.1b Network Performance (Bandwidth, Latency & Factors)
OCR J277 · GCSE Computer Science · ~12 min read
Notes
Video
Slides
Worksheet
Quiz

Bandwidth

Bandwidth is the maximum amount of data that can be transmitted over a network connection per second. It is measured in bits per second (bps), typically expressed as Mbps or Gbps.

Think of bandwidth like a pipe — a wider pipe allows more water to flow through per second. Higher bandwidth = more data can be transmitted per second = faster network.

UnitMeaningTypical use
KbpsKilobits per second (1,000 bps)Slow dial-up
MbpsMegabits per second (1,000,000 bps)Home broadband (10–1000 Mbps)
GbpsGigabits per second (1,000,000,000 bps)Wired LAN, data centres

Higher bandwidth → more data can be transmitted per second → files download faster, video streams more smoothly.

Latency

Latency is the delay between sending data and receiving it — the time it takes for a signal to travel from source to destination and back. It is measured in milliseconds (ms). Also called "ping" in gaming contexts.

  • Low latency (e.g. <20 ms) → real-time applications work well (gaming, video calls)
  • High latency (e.g. >200 ms) → noticeable delay; problematic for real-time applications

Bandwidth and latency are different: high bandwidth does not guarantee low latency. A satellite connection may have very high bandwidth but also high latency (~600 ms) due to the signal's 35,000 km journey.

Factors Affecting Network Performance

Several factors affect how well a network performs:

1. Bandwidth of the connection

Higher bandwidth allows more data per second. Sharing bandwidth among many users reduces effective speed for each user.

2. Number of connected devices / network traffic

More devices connected and using the network simultaneously → bandwidth is shared → each device gets a smaller share → slower performance.

3. Transmission media

MediaMax speedNotes
Fibre optic cableHundreds of GbpsLight signals, very fast, low interference
Ethernet (copper)10 Mbps–10 GbpsReliable, common in offices
Wi-Fi (wireless)Up to ~9.6 Gbps (Wi-Fi 6)Affected by distance, walls, interference
SatelliteTens of MbpsVery high latency (~600 ms); used in remote areas

4. Interference and signal degradation

Wireless networks are affected by interference from other devices (microwave ovens, other Wi-Fi networks), physical barriers (walls, floors), and distance from the access point. Copper cables can suffer from electromagnetic interference (EMI). Fibre optic cables are immune to EMI.

5. Error rate

If data packets are frequently corrupted or lost, they must be retransmitted. High error rates reduce effective throughput.

6. Wired vs Wireless

FactorWired (Ethernet)Wireless (Wi-Fi)
SpeedHigher, consistentVariable — affected by distance, walls
ReliabilityVery reliableLess reliable; prone to interference
SecurityMore secure (physical access needed)Less secure (signals travel through air)
MobilityLimited — device must be cabledHigh — devices can move freely
SetupRequires cables, trunkingEasier setup — no cables needed
Exam tip: Know the four main factors affecting network performance: bandwidth, number of connected devices, transmission media, and interference. When asked to explain why a network is slow, name the factor AND explain the mechanism — e.g. "More devices share the available bandwidth, so each device receives less data per second." Bandwidth ≠ latency — make sure you distinguish these clearly.
⚠️ Common Mistakes
  • Confusing bandwidth and speed — bandwidth is the maximum capacity; actual speed (throughput) may be lower
  • Saying "high latency means slow download speeds" — high latency causes delay, not necessarily slow throughput
  • Forgetting that more devices sharing a connection reduces performance for each device
  • Saying "wired is always better than wireless" without qualification — wireless has the advantage of mobility
  • Not explaining the mechanism when answering why performance is poor
✅ Notes completed!
▶
Video coming soon

What's in this video

  • • Bandwidth: definition, units, how it affects performance
  • • Latency: delay, milliseconds, difference from bandwidth
  • • Four factors affecting network performance
  • • Wired vs wireless comparison
Click slide or press arrow keys to navigate

Worksheet — 1.3.1b Network Performance

8 questions · 22 marks

Q1What is bandwidth and what unit is it measured in?[2]
✅ Mark scheme
Bandwidth is the maximum amount of data that can be transmitted over a network connection per second [1]; measured in bits per second (bps), Mbps, or Gbps [1].
Q2What is latency? How does it differ from bandwidth?[3]
✅ Mark scheme
Latency is the delay between sending and receiving data, measured in milliseconds [1]; bandwidth is the maximum data transfer rate [1]; they are different — high bandwidth does not guarantee low latency [1].
Q3A school has 30 computers all connected to the same 100 Mbps connection. Explain how this affects the performance each computer experiences.[2]
✅ Mark scheme
The 100 Mbps bandwidth is shared between all 30 computers [1]; when all are active, each gets approximately 100/30 ≈ 3.3 Mbps — much less than the full connection [1].
Q4State four factors that can affect network performance.[4]
✅ Mark scheme
1. Bandwidth of the connection [1]; 2. Number of connected devices / network traffic [1]; 3. Transmission media used (fibre vs copper vs Wi-Fi) [1]; 4. Interference / error rate [1].
Q5Explain why a fibre optic cable provides better network performance than a copper Ethernet cable.[2]
✅ Mark scheme
Fibre optic cables transmit data as light signals at much higher speeds / hundreds of Gbps [1]; they are immune to electromagnetic interference (EMI), unlike copper cables, so fewer errors and retransmissions [1].
Q6State two advantages and two disadvantages of wireless (Wi-Fi) compared to a wired (Ethernet) connection.[4]
✅ Mark scheme
Advantages: mobility — devices can move freely [1]; easier setup, no cabling required [1]; Disadvantages: lower/variable speeds affected by distance and walls [1]; less secure as signals travel through air / easier to intercept [1].
Q7A gamer complains of high ping (latency) while playing online. Explain what this means and suggest one possible cause.[2]
✅ Mark scheme
High ping means there is a long delay between the gamer's input and the game server's response [1]; possible cause: congested network / using Wi-Fi far from the router / too many devices connected / distance to server [1].
Q8Explain why a satellite internet connection might have high bandwidth but still be poor for real-time gaming.[3]
✅ Mark scheme
Satellite broadband can offer high bandwidth (data transfer rate) [1]; but the signal must travel 35,000 km to the satellite and back, causing very high latency (~600 ms) [1]; in real-time gaming, high latency causes noticeable delay between player actions and server response, making the game unplayable [1].
?
out of 22 — self-mark above
Topic Quiz
Question 1 of 15
You scored
out of 15
Card 1 of 15
Click to reveal definition
🎉
Complete!
TermDefinition
🎯

Mini Test — 1.3.1b Network Performance

10 questions · 10 marks · 10 minutes

← 1.3.1a Types of Networks 1.3 Computer Networks 1.3.1c Network Hardware →
🔒
Unlock Everything
Subscribe to access all OCR J277 lessons.
£7.99/month
or £59/year
Subscribe now →