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J277 1.3 Network performance, connections and encryption

Part 3 of 7 · J277 1.3 · Networks

What makes a network fast, how devices connect, and why data in transit is encrypted.

Students will:

  • explain the factors that affect network performance
  • compare wired Ethernet with wireless connections
  • distinguish Wi-Fi from Bluetooth by suitable use
  • recommend connection modes for a scenario
  • explain the principle of encryption

Inside: 5 explanation cells, 4 multiple-choice questions, 3 fill-in-the-blanks cells and 3 written answers. 39 marks, about 75 minutes.

Series: J277 1.3 · Networks, part 3 of 7.

Shared by Coding PathwayVerified teacher

  • 15 cells
  • About 75 minutes
  • CC BY-SA 4.0
  • Shared 17 Aug 2026
  • Updated 9 Sept 2026

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The whole resource, exactly as a class sees it. Answers and marking are held back.

Networks 3: performance, connections and encryption

A network design must transfer data well, suit the way devices are used and protect data in transit.

By the end, you should be able to:

  • explain factors that affect network performance
  • compare wired Ethernet with wireless connections
  • distinguish Wi-Fi from Bluetooth by suitable use
  • recommend one or more connection modes for a scenario
  • explain the principle of encryption

Strong answers use cause and effect. Do not write only more users makes it slower or wired is better. Work through the explanation, checks and applications in order. Use the final challenge to connect several network ideas.

1. What affects network performance?

Bandwidth is the maximum amount of data that a connection can transfer in a given time. Higher bandwidth allows more data to be transferred each second, but the available capacity is shared by active devices and tasks.

Important factors include:

  • number of connected or active devices: more devices compete for the available bandwidth, so each may wait longer and latency can increase
  • available bandwidth: a higher-capacity connection can transfer more data per second
  • transmission medium: fibre, copper Ethernet and wireless links have different capacities and reliability
  • wireless interference, obstacles and distance: competing signals, walls and weak signal strength can corrupt or lose data
  • network hardware: an overloaded or low-performance switch, router or server can become a bottleneck
  • amount and type of traffic: video calls and large downloads use more bandwidth than short text messages
  • packet loss and transmission errors: affected data may need to be retransmitted, reducing effective network performance

Build an explanation as a chain. Higher bandwidth means more data can be transferred in the same time, so waiting can decrease and performance can improve. More active users share the available bandwidth, so less may be available to each device and transfers can take longer. A definition alone does not explain the performance effect.

Fill in the blanks4 marks
The amount of data that can be transferred in a given time is the label 1. As the number of label 2 increases, each may have less capacity available. Wireless label 3 can cause errors, while overloaded hardware can become a label 4.
  • bottleneck
  • bandwidth
  • interference
  • hosting
  • active devices
  • latency
Multiple choice1 mark

Thirty students begin streaming video over the same school connection. Pages that loaded quickly before now take longer. What is the best explanation?

  • AThe active devices are sharing the available bandwidth
  • BThe school LAN has automatically become a WAN
  • CEach video gives the connection more bandwidth
  • DEncryption has removed the network addresses
Written answer4 marks

Explain two factors that could make a wireless school network perform poorly during a busy lesson.

For each factor, name it, explain what changes, and state the effect on data transfer or waiting time.

Students type their answer here.

2. Wired and wireless connections

Ethernet is a wired method of connecting devices. A physical copper or fibre-optic cable connects through a wired network interface controller or card (NIC). Ethernet commonly provides high and consistent bandwidth, low interference and a stable connection. An attacker normally needs access to the cable or network equipment to intercept the signal. However, cables restrict movement, take time and money to install, and can be damaged or create trip hazards.

Wi-Fi connects devices wirelessly to a local network using a wireless network interface controller, sometimes called a WNIC. It supports movement and makes it easier to add portable devices without installing a cable to each one. Performance can be reduced by distance, walls, competing radio signals and many active devices. Wireless signals can extend beyond a building, so strong security is important.

Bluetooth is a short-range wireless connection often used between nearby devices, such as a computer and a headset, keyboard or sensor. It is convenient and uses relatively little power, but its range and bandwidth are usually lower than Wi-Fi.

A mixed design is common: Ethernet for fixed devices needing consistent performance, Wi-Fi for mobile devices, and Bluetooth for short-range peripherals.

Wi-Fi is a way to join a local network wirelessly. It does not itself mean that the network has an Internet connection: a device can use Wi-Fi to reach local resources even when Internet access is unavailable.

Fill in the blanks8 marks
label 1 normally uses a label 2 connected through a label 3. label 4 uses a label 5 and provides greater label 6, but can suffer from label 7. label 8 suits short-range links between nearby devices.
  • bandwidth
  • interference
  • Ethernet
  • mobility
  • physical cable
  • Wi-Fi
  • Bluetooth
  • wireless NIC
  • NIC
Multiple choice1 mark

A tablet is connected to the school LAN by Wi-Fi, but the school's Internet connection has failed. What can be concluded?

  • AThe tablet must switch to Bluetooth to open local files
  • BWi-Fi has failed because Wi-Fi and the Internet are the same service
  • CThe tablet may still reach local network resources, but cannot reach Internet services through the failed connection
  • DThe wireless access point becomes a web server automatically
Multiple choice, several answers3 marks

Which are possible drawbacks of a wireless network connection? Select all that apply.

  • AEvery device must remain attached to a network cable
  • BWalls and other radio signals can cause interference
  • CIt cannot connect portable devices
  • DThe signal has a limited range
  • EAn unauthorised user may try to connect or intercept data
Written answer6 marks

A school is equipping a room with fixed gaming computers, teacher tablets and wireless headsets. Recommend a suitable connection for each type of device and justify your choices.

For each device, use: 'I recommend... because...'. Consider interface hardware, consistent bandwidth, movement, range, interference and purpose.

Students type their answer here.

3. Encryption protects data in transit

Encryption uses an algorithm and a key to transform readable plaintext into ciphertext. A suitable key is needed to decrypt the ciphertext back into the original data.

If encrypted data is intercepted while crossing a wired or wireless connection, it should be meaningless and cannot be understood by someone who does not have the key. Encryption reduces the harm caused by interception. It does not stop data from being captured, increase bandwidth, stop a cable being cut or replace user authentication.

Encryption protects confidentiality even if data is intercepted. It does not stop an attacker from obtaining a copy of the ciphertext.

Plaintext encrypted to ciphertext and decrypted with a key Readable plaintext and a key enter encryption. Unreadable ciphertext can travel across a network and may be intercepted. Decryption with the correct key restores readable plaintext. Encryption changes readability, not interceptability PLAINTEXT readable data ENCRYPT use an algorithm + key CIPHERTEXT unreadable without the key may still be intercepted DECRYPT correct key restores readable plaintext Without the correct key, an intercepted copy should remain unintelligible.
Fill in the blanks5 marks
Encryption applies an label 1 and a label 2 to readable label 3, producing label 4. It makes captured data meaningless without the key but does not prevent label 5.
  • ciphertext
  • key
  • plaintext
  • algorithm
  • interception
  • bandwidth
Multiple choice1 mark

Which statement best describes the protection provided by encryption?

  • AEncrypted data cannot be intercepted
  • BIntercepted ciphertext should be meaningless without the correct key
  • CEncryption increases wireless signal range
  • DEncryption replaces the need for user authentication
Written answer6 marks

Challenge: a crowded exhibition hall has 80 fixed ticket desks, staff tablets and many competing wireless signals. The network is slow and sometimes loses connections. Recommend a connection plan and two other changes that could improve performance or security.

Use one paragraph per recommendation: 'Change... because... Therefore...'. Apply Ethernet, Wi-Fi, bandwidth, demand, interference, hardware capacity and encryption.

Students type their answer here.

Final check

Without looking back, write two complete performance chains in the form factor, network effect, user consequence. Then choose a suitable connection for one fixed device, one mobile device and one short-range peripheral.

Check that you can:

  • explain how bandwidth, device demand, interference, media, hardware and errors affect performance
  • compare specific benefits and drawbacks of wired and wireless connections
  • recommend Ethernet, Wi-Fi or Bluetooth for a scenario
  • explain that encryption makes intercepted ciphertext meaningless without the key rather than preventing interception