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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: 4 text sections, 2 multiple-choice activities, 2 completion activities, 6 written answers. 20 marks. Suggested teaching time: 40–60 minutes. 2 diagrams.

Includes a teacher guide with suggested sections, timings and common misconceptions.

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

Shared by Coding PathwayVerified teacher

  • 14 cells
  • About 45 minutes
  • CC BY-SA 4.0
  • Shared 17 Aug 2026
  • Updated 27 Oct 2026

Preview

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

Network performance, connections and encryption

A connection must suit the device and the task. First consider how much data needs to move, then choose a connection and protect the data travelling across it.

1. Sharing a connection

Bandwidth is the maximum amount of data a connection can transfer per second. More bandwidth allows more data to move in the same time. It does not make every part of a network faster.

FactorPossible effect
More active users or large transfersThey share the available bandwidth; transfers may take longer.
Higher bandwidthMore data can be transferred per second, reducing waiting.
Walls, distance or radio interferenceWireless signals may weaken or data may need to be sent again.
Transmission medium or overloaded equipmentA slower link, switch, router or server can limit the rest of the network.

The same connection may have to support more transfers at once. Less capacity may then be available to each transfer. A connected device that is idle is not creating the same demand as one downloading a large file.

Sharing the same connection Two bars show the same total bandwidth. In an illustrative equal split, two active transfers A and B each have half a bar; four active transfers A, B, C and D each have a quarter. These are example shares, not a guarantee of equal allocation. Real shares depend on use and equipment. Same total bandwidth Two active transfers A B Four active transfers A B C D Equal shares shown only as an example. Real shares depend on use and equipment.
Fill in the blanks2 marks
A connection's maximum data transfer per second is its Answer 1. If many devices transfer data at once, they Answer 2 that capacity.
  • bandwidth
  • share
  • hosting
  • increase
Written answer2 marks

A studio increases the bandwidth of its network connection. Explain how this could improve file transfers.

Students type their answer here.

Written answer2 marks

More students begin downloading files over a college network. Its bandwidth stays the same. Explain how this could affect each student's download.

Students type their answer here.

2. Match the connection to the task

An Ethernet connection uses a cable through a wired network interface controller/card (NIC). Ethernet can use copper or fibre-optic cable. Copper carries electrical signals; fibre carries light and is useful for high-capacity links over longer distances. This does not mean every fibre link is faster than every copper link.

ConnectionUseful featuresLimitations
EthernetOften a steady connection for fixed devices; less affected by radio interference.A cable limits movement and takes work to install.
Wi-FiRadio links connect portable devices to a LAN without a cable to each device.Walls, range, interference and shared demand can affect performance.
BluetoothA short-range radio link, often for a nearby headset, mouse or keyboard; usually uses little power.Usually lower range and bandwidth than Wi-Fi.

Wireless devices need a wireless network interface. Wi-Fi is not the Internet: local resources may still work when a network's Internet connection fails. Compare the actual equipment and situation; wireless is not always slower or less secure.

Fill in the blanks3 marks
Choose the usual connection for each task. (a) A cable from a desktop PC to a switch: Answer 1. (b) A tablet joining a LAN without a cable: Answer 2. (c) A headset linking directly to a nearby laptop: Answer 3.
  • Bluetooth
  • Ethernet
  • Wi-Fi
  • DNS
Written answer2 marks

An animation club has fixed desktop PCs. Their Wi-Fi links suffer from radio interference. Recommend a connection for these PCs and explain one reason for your choice.

Students type their answer here.

Written answer2 marks

Gallery staff carry tablets between displays. Recommend a connection from the tablets to the gallery LAN and explain one reason for your choice.

Students type their answer here.

Written answer2 marks

A student uses a wireless headset beside a laptop. Recommend a connection between these two devices and explain one reason for your choice.

Students type their answer here.

Multiple choice1 mark

A club adds Wi-Fi to an existing wired LAN. Which is a possible drawback of the new Wi-Fi links?

  • AEach tablet must stay attached to a network cable
  • BThey cannot reach any local resources
  • CWalls and other radio signals can weaken or disrupt them
  • DThey automatically remove the need for a router
Multiple choice1 mark

A tablet remains connected to a working school Wi-Fi LAN after the Internet connection fails. What may still be possible?

  • AOpening a file on a working local file server
  • BOpening every Internet website as usual
  • CReceiving an IP address from Bluetooth instead
  • DTurning the access point into an Internet provider

3. Protect data while it travels

Encryption uses an algorithm and a key to turn readable plaintext into ciphertext. The intended recipient uses a suitable key to decrypt it.

Someone may still intercept a copy. The protection is that the ciphertext should not be understandable without the key. Encryption does not increase bandwidth or prevent a cable being cut.

Encryption across a network Readable plaintext is encrypted using a key. Ciphertext travels across the network and can still be copied. The intended recipient uses a suitable key to decrypt it into readable data. Plaintext Readable data Encrypt using a key Ciphertext Not understandable without the key Across the network Intended recipient Uses a key to decrypt the data A copy can still be intercepted.
Written answer3 marks

A charity sends volunteers' personal details across a network. Explain how encryption protects these details if someone intercepts a copy.

Students type their answer here.

Review

Read one of your explanations again. Check that it connects a feature of the network or connection to what happens in the situation.