A-LevelComputer ScienceCommunication and internet technologies9618/12 · Oct/Nov 2025 · Q513 Marks

A local area network (LAN) has five computers, one switch and one server.

(a)Describe the characteristics of a LAN.[2]
(b)Complete the following diagram to show how these devices are connected in a star topology. [Diagram with Computer, Computer, Computer, Computer, Computer, Server, Switch boxes][2]
(c)Describe how packets are transmitted between two hosts using a star topology.[3]
(d)Another type of network is a bus network. Ethernet is used to transmit and receive data between the devices on the bus network. Describe how collisions are detected and managed on this network.[3]
(e)Complete the table by identifying one threat to computer and data security posed by networks and the internet. Describe the threat and give a method of prevention. Threat Description Prevention[3]

This question uses a diagram from the original paper, which isn't shown here. Open the full paper from the past papers archive to see it.

Mark scheme

Marking points from the official mark scheme (Oct/Nov 2025). The mark or mark type is shown in brackets.

5(a) 1 mark per bullet point, max 2 marks
Covers a small geographical area
Normally privately owned / dedicated infrastructure
Can use wired or wireless communication
5(b) 1 mark per bullet point, max 2 marks
All computers directly connected to switch and no other connections
Switch connected directly to server
[Diagram showing all computers and server connected to the switch]
5(c) 1 mark per bullet point, max 3 marks
The sending device sends the packets to the switch
The switch checks the destination address on each packet
and sends them only to the intended receiver
5(d) 1 mark per bullet point, max 3 marks
The use of CSMA/CD // Carrier Sense Multiple Access with Collision Detection
The workstations listen to the communication channel
and send data only when there is no data being transmitted / the line is idle
If a collision is detected, transmission is aborted
and a jamming signal is sent
The workstation calculates a random wait time before trying to re-transmit
The random time is increased if there are multiple collisions
5(e) 1 mark for correct threat 1 mark corresponding description 1 mark for correct method of prevention
Threat: Malware / Virus - Description: Malicious code that can alter/delete files - Prevention: Anti-virus // Anti-malware // Firewall
Threat: Spyware - Description: Records keystrokes which are sent to third party - Prevention: Anti-spyware // Firewall // Anti-malware
Threat: Hacking - Description: Gaining unauthorised access to a computer network / device - Prevention: Authentication // Firewall
Threat: Phishing - Description: Emails supposedly from reputable companies are sent to trick people into revealing personal information - Prevention: Use a spam filter // Do not open emails from unknown sources
Threat: Pharming - Description: Users are directed to a bogus website that looks legitimate to obtain personal information - Prevention: Use a VPN // Anti-malware// Do not open links or download attachments