Networking Concepts

What you'll learn

• The seven layers of the OSI model and each layer's role
• How the TCP/IP model compares to the OSI model
• IPv4 vs IPv6 addressing
• Types of network devices and what each one does
• Cybersecurity basics — malware types, passwords, and HTTPS

Key concepts

1. OSI Model — 7 Layers

The OSI (Open Systems Interconnection) model is a conceptual framework that standardises how different computer systems communicate over a network. It has 7 layers, each with a specific role.

Memory aid — layers 7 to 1: All People Seem To Need Data Processing

Key layer roles to remember:

• Layer 7 (Application): What the user interacts with — web browsing (HTTP), email (SMTP)
• Layer 4 (Transport): TCP ensures all data arrives correctly; UDP is faster but no guarantee
• Layer 3 (Network): IP addresses live here; routers work at this layer
• Layer 2 (Data Link): MAC addresses live here; switches work at this layer
• Layer 1 (Physical): Actual electrical signals, light pulses, or radio waves

2. TCP/IP Model vs OSI Model

The TCP/IP model (also called the Internet model) is the practical model actually used on the internet. It has 4 layers that map approximately to the OSI model's 7 layers.

Comparison table:

OSI is like a blueprint — it tells you how things should work. TCP/IP is like the actual building — it's how the internet actually works.

3. IP Addressing — IPv4 vs IPv6

An IP address is a unique numerical label assigned to every device on a network, used for identification and communication.

IPv4 (Internet Protocol version 4)

• Format: 4 groups of numbers, each 0–255, separated by dots
• Example: 192.168.10.1
• Total possible addresses: about 4.3 billion (2³²)
• Problem: The world is running out of IPv4 addresses due to billions of internet-connected devices

IPv6 (Internet Protocol version 6)

• Format: 8 groups of hexadecimal digits, separated by colons
• Example: 2001:0db8:85a3:0000:0000:8a2e:0370:7334
• Total possible addresses: 340 undecillion (3.4 × 10³⁸) — effectively unlimited
• Developed to replace IPv4 as the internet expanded

IPv4 vs IPv6 comparison:

4. Network Devices — Comparison Table

Simple analogy:

• Hub = Shouting in a room (everyone hears)
• Switch = Passing a note directly to one person (only the target receives it)
• Router = Post office (decides which road each letter should travel)
• Modem = Translator (converts digital language to phone line language)
• Firewall = Security guard (checks who is allowed in and out)

5. Cybersecurity Basics

Cybersecurity is the practice of protecting computers, networks, and data from digital attacks and unauthorised access.

Types of Malware

Malware (malicious software) is any software designed to harm, disrupt, or gain unauthorised access to a system.

Strong Passwords

A strong password is your first line of defence against unauthorised access.

Strong password checklist:

Weak vs Strong password examples:

HTTPS and Safe Browsing

Quick check

1. Match each OSI layer to its function: (a) Layer 1 — (b) Layer 3 — (c) Layer 7. Choose from: [Transmits raw bits] [Routes data using IP addresses] [User-facing applications like HTTP].

2. How many layers does the TCP/IP model have, and how do they map to the 7 layers of the OSI model?

3. What is the main reason IPv6 was developed to replace IPv4?

4. A company wants to prevent unauthorised users from accessing its internal network from the internet. Which network device should they use, and why?

5. A student receives an email with an attachment that says "Click to get free games." They download and open it — now their files are encrypted and they are asked to pay money. What type of malware is this?

Open the Practice tab for graded questions on Networking Concepts.