10 January 2026

A-Level Computing: Networking Basics – How Data Moves Across the Internet

When a student clicks “send”, “submit”, or “play video”, something remarkable happens in the background. Data doesn’t travel as a single stream from one computer to another; instead, it is broken up, labelled, routed, checked, and reassembled—often across thousands of kilometres in milliseconds.

Understanding how data moves across the internet is a core part of A-Level Computing, and it’s one of those topics that really benefits from thinking step-by-step.

1️⃣ From Message to Packets

Data is first broken into packets. Each packet contains:

A small chunk of the data
The source IP address
The destination IP address
A packet number for reassembly

This process is called packet switching, and it’s why the internet is so resilient. If one route fails, packets can simply take another path.

2️⃣ Protocols: The Rules of the Internet

For packets to be understood, everyone must follow the same rules:

TCP (Transmission Control Protocol) ensures packets arrive correctly and in order
IP (Internet Protocol) handles addressing and routing
HTTP/HTTPS manage web page requests
DNS translates domain names (like websites) into IP addresses

Students often find it helpful to think of protocols as agreements that make global communication possible.

3️⃣ Routers, Switches, and Paths

Packets hop from one router to another across networks:

Routers read the destination IP address
They decide the best next hop based on routing tables
Different packets from the same message may take different routes

This explains why latency can vary and why networks cope well with congestion.

4️⃣ Client–Server Communication

Most internet activity uses a client–server model:

The client (your device) requests data
The server responds with packets
The connection may be short-lived (loading a webpage) or persistent (video streaming)

This model underpins email, websites, cloud storage, and online gaming.

5️⃣ Layers Make It Manageable

Networking is taught using layered models:

Application layer – what the user sees
Transport layer – reliability and flow control
Network layer – addressing and routing
Physical/Data layers – cables, signals, and hardware

Breaking networking into layers helps students understand complex systems without being overwhelmed.

Why This Matters for A-Level Students

✔ Appears frequently in exam questions
✔ Links theory to real-world systems
✔ Builds foundations for cybersecurity, software development, and networking careers

Once students grasp packet switching + protocols + routing, the internet stops being “magic” and starts making sense.

10 January 2026