LANs and WANs

• A LAN (Local Area Network) covers a small area — one building or site, like a school or home. Usually one organisation owns all the hardware and cabling.
• A WAN (Wide Area Network) covers a large geographic area — cities, countries, the world. It often uses third-party infrastructure (telephone lines, fibre, satellites). The internet is the largest WAN.

Benefits of networking: share files, share hardware (e.g. one printer), communicate, and access data centrally. Drawbacks: cost, security risks and the need to manage it.

LAN or WAN?

Network topologies

A topology is the shape of how devices are connected. Two common ones:

• Star — each device has its own cable to a central switch. Reliable (one cable failing affects only one device) but needs the central switch to work.
• Mesh — devices connect to many others, so data has several possible routes; very resilient but needs lots of connections.

Wired vs wireless

• Wired (e.g. Ethernet cable, fibre) — usually faster, more reliable and more secure, but you can't move around freely and cabling costs more to install.
• Wireless (e.g. Wi-Fi, Bluetooth) — convenient and mobile, no cables, but can be slower, suffer interference, and is easier to intercept if not encrypted.

Exam point: wireless is more convenient but wired is generally faster and more secure. Choose based on the situation (mobility vs speed/security).

LAN, WAN or both?

Tap a statement, then tap where it belongs. (Some are true of both.)

Protocols

A protocol is a set of rules that lets devices communicate. Key ones:

• TCP/IP — the core pair: TCP splits data into packets and reassembles them; IP handles addressing and routing.
• HTTP / HTTPS — web pages; HTTPS is the encrypted, secure version.
• FTP — transferring files. SMTP — sending email; IMAP/POP3 — receiving email.
• Ethernet — wired LANs; Wi-Fi — wireless.

Why protocols? Without agreed rules, devices from different makers couldn't understand each other. Protocols make the internet work between billions of devices.

The TCP/IP four-layer model

Network software is split into layers, each with its own job. This keeps things manageable — a change in one layer doesn't break the others. Edexcel uses the four-layer TCP/IP model:

Layer jobs: Application = the program's data (web, email); Transport (TCP) = split into packets and reassemble; Internet (IP) = addressing and routing; Link = the physical/hardware transmission.

Which layer?

The internet & packet switching

The internet is a global network of networks. Data sent across it is broken into small packets in a process called packet switching:

• Data is split into numbered packets, each carrying the destination address and its position.
• Packets can travel by different routes and may arrive out of order.
• At the destination they are reassembled in the correct order using their numbers; missing packets are re-sent.

Why it's clever: if one route is busy or fails, packets simply take another path — making the network resilient and efficient. Each packet also carries a header (addresses, packet number) and the payload (the actual data).

Packet switching

Your turn — counting packets

Match the task to the protocol

Tap a task on the left, then its matching protocol on the right.

Network security threats

Networks face many threats. Key ones for Edexcel:

• Malware — malicious software: viruses, worms, trojans, ransomware, spyware.
• Phishing — fake emails/messages tricking users into revealing passwords or bank details.
• Brute-force attack — trying many passwords until one works.
• Denial of Service (DoS) — flooding a server with traffic so it can't respond.
• Data interception — "sniffing" data as it travels, especially on unsecured wireless.
• SQL injection — entering malicious database commands into an input box.

Human weakness: many attacks (like phishing) target people, not just machines — so user training matters as much as technology.

Preventing attacks

• Firewall — filters incoming/outgoing traffic to block unauthorised access.
• Anti-malware software — detects and removes malicious software.
• Encryption — scrambles data so intercepted data is unreadable without the key.
• Strong passwords & two-factor authentication — resist brute-force and stolen-password attacks.
• User access levels & permissions — limit what each user can see or change.
• Penetration testing & updates — find and patch weaknesses before attackers do.

Layered defence: no single measure is enough. Combining firewalls, encryption, strong authentication and educated users gives the best protection.

Name the threat

Pick the defence

Which topology?

Your turn — download time

The big ideas to know

You've covered the whole of Edexcel Networks. Press Finish to see your score.