Learn this topic properly. Interactive diagrams, worked examples, check questions and exam-style practice with mark schemes. Open “A2 · Networks” in FortyFive →
Local area network (small area) / wide area network (large geographical area, e.g. the internet).
Protocol
An agreed set of rules for communication.
Packet switching
Data is split into packets that travel independently and are reassembled at the destination.
Client–server / peer-to-peer
Central servers provide services / all devices share resources equally.
Devices: switch (connects devices in a LAN using MAC addresses), router (forwards packets between networks using IP addresses), wireless access point, modem, NIC.
The full notes, worked example and check questions for this subtopic are in the app.
Exam tip: Know one protocol per layer and what it does: examiners like matching protocols to layers.
A2.2Data transmission and addressing
Key terms
IP address
A logical address identifying a device on a network (IPv4 32-bit, IPv6 128-bit).
MAC address
A unique physical address of a network interface (48-bit).
Bandwidth
The maximum rate of data transfer (bits per second).
Latency
The delay before data begins to arrive.
IPv4 has about 4.3 billion addresses (\(2^{32}\)); IPv6 (\(2^{128}\)) solves address exhaustion. NAT lets many private devices share one public IP.
The full notes, worked example and check questions for this subtopic are in the app.
Exam tip: Watch the units: network speeds are in bits per second, file sizes in bytes.
A2.3Network security
Key terms
Encryption
Converting data into ciphertext so only authorized parties can read it.
Symmetric encryption
The same key encrypts and decrypts.
Asymmetric encryption
A public key encrypts; only the matching private key decrypts.
Firewall
Monitors and filters network traffic according to rules.
Hashing
A one-way function producing a fixed-length digest, used to store passwords and check integrity.
Threats: malware (viruses, worms, ransomware, trojans), phishing, denial of service (DDoS), man-in-the-middle, SQL injection, brute-force password attacks.
The full notes, worked example and check questions for this subtopic are in the app.
Exam tip: Match each threat to a specific countermeasure rather than listing general security advice.