4.1d Network Speed & Performance — Edexcel 1CP2

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Bandwidth

Bandwidth is the maximum amount of data that can be transmitted over a network connection in a given time. It is measured in bits per second (bps) — most commonly Mbps (megabits per second) or Gbps (gigabits per second).

Higher bandwidth = more data can be sent at once
Bandwidth is the capacity of the connection, not necessarily the actual speed
Analogy: bandwidth is like the width of a road — wider road = more cars at once

Latency

Latency is the delay between sending data and it being received. It is measured in milliseconds (ms).

Low latency = less delay = faster response (important for gaming, video calls, online transactions)
High latency causes lag
Latency is affected by: distance data must travel, number of routers/hops it passes through, congestion on the network

Factors Affecting Network Performance

Factor	Effect on performance
Bandwidth	Higher bandwidth = more data can be sent simultaneously
Number of users	More users sharing the same connection = slower speeds for each
Type of connection	Wired (Ethernet/fibre) faster than wireless (Wi-Fi)
Network congestion	Too much data on the network causes slower speeds and higher latency
Distance	Greater distance = more signal degradation and higher latency
Interference (wireless)	Walls and other devices can reduce wireless signal strength
Hardware quality	Older/slower routers, switches, and cables limit throughput
Packet loss	Lost data packets must be retransmitted, slowing performance

Bandwidth Units

Unit	Full name	Equivalent
bps	bits per second	base unit
Kbps	kilobits per second	1,000 bps
Mbps	megabits per second	1,000,000 bps
Gbps	gigabits per second	1,000,000,000 bps

Bandwidth vs Speed

Bandwidth and speed are often confused but are different:

Bandwidth = maximum capacity (how wide the "pipe" is)
Speed (throughput) = actual rate of data transfer achieved in practice
Actual throughput is often lower than stated bandwidth due to congestion, distance, and interference

Exam tip: Know that bandwidth is measured in bits per second (bps), not bytes. "50 Mbps" means 50 megabits per second. State at least 3 factors that affect network performance for 3-mark questions.

⚠️ Common Mistakes

Confusing bandwidth (capacity) with speed (actual throughput)
Saying bandwidth is measured in bytes per second — it's bits (bps, Mbps, Gbps)
Not mentioning congestion or number of users as factors affecting performance
Confusing latency (delay) with bandwidth (capacity)

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Worksheet — 4.1d Network Speed & Performance

8 Edexcel-style questions · AI-marked

Q1What is bandwidth and how is it measured?[2]

✅ Mark scheme

Bandwidth is the maximum amount of data that can be transmitted over a network connection in a given time [1]; measured in bits per second (bps), e.g. Mbps or Gbps [1].

Q2What is latency?[1]

✅ Mark scheme

Latency is the delay between sending data and it being received at the destination, measured in milliseconds (ms) [1].

Q3State three factors that can affect the performance of a network.[3]

✅ Mark scheme

Any three from: bandwidth of the connection [1]; number of users sharing the connection [1]; network congestion [1]; type of connection (wired/wireless) [1]; distance data must travel [1]; interference (for wireless) [1]; hardware quality [1].

Q4Explain why more users on a network can slow it down.[2]

✅ Mark scheme

The available bandwidth is shared between all users [1]; as more users transmit data simultaneously, each user receives a smaller share of the bandwidth, reducing their individual speed [1].

Q5Explain the difference between bandwidth and throughput.[2]

✅ Mark scheme

Bandwidth is the maximum capacity/potential speed of a connection [1]; throughput is the actual data transfer rate achieved in practice, which is usually lower than bandwidth due to congestion, distance, or interference [1].

Q6Convert 1 Gbps into Mbps.[1]

✅ Mark scheme

1 Gbps = 1,000 Mbps [1].

Q7Why does a video call have poor quality when there is high latency on the network?[2]

✅ Mark scheme

Latency causes a delay between data being sent and received [1]; for video calls, this means audio and video arrive late, causing freezing, lag, or out-of-sync audio and video [1].

Q8A student says "my broadband is 100 Mbps so my downloads always run at 100 Mbps." Is this correct? Explain.[2]

✅ Mark scheme

No — 100 Mbps is the bandwidth (maximum capacity) [1]; the actual throughput (speed achieved) is often lower due to congestion, distance, interference, and other users sharing the connection [1].

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Bandwidth

Latency

Factors Affecting Network Performance

Bandwidth Units

Bandwidth vs Speed

Worksheet — 4.1d Network Speed & Performance

Mini Test — Network Speed & Performance