O-Level Computing (7155) Networks and the Internet: network types, IP addresses and protocols, the internet and the World Wide Web, security threats and protection measures

Why this module matters

Networks and the Internet explains how computers connect, communicate and stay secure, the everyday reality behind email, web browsing and online services. This module teaches you the types of network, how data is addressed and sent, the difference between the internet and the web, and how to protect a network from the most common threats. It is a theory module examined in the written Paper 1, and it rewards precise definitions and clear explanations.

This guide ties together the matching dot-point pages, each with its own worked detail and practice. The strands below move from connecting computers to securing them.

Networks and network types

Start with what a network is and the two main types. See networks and network types for the definitions and the benefits and drawbacks.

A computer network is two or more computers connected together so they can share data and resources. A LAN (local area network) covers a small area such as one school or office; a WAN (wide area network) spans a large geographical area, such as between cities, and the internet is the largest example. Networking brings benefits (sharing files, printers and an internet connection, and central management) but also drawbacks (cost of equipment, the risk of one fault affecting many users, and greater exposure to security threats).

IP addresses, protocols and packets

Next, how data is addressed and carried. See IP addresses and protocols for how this works.

Every device on a network has an IP address, a unique number that identifies it so data can be sent to the right place. A protocol is an agreed set of rules that governs how data is formatted and exchanged, so different devices can communicate. Data is broken into packets, small chunks that travel across the network and are reassembled at the destination; splitting data into packets lets the network route them efficiently and resend any that are lost.

The internet and the World Wide Web

These are often confused, and the distinction is examinable. See the internet and the World Wide Web for the difference and how a page loads.

The internet is the global network of interconnected computers and the infrastructure linking them; it carries many services. The World Wide Web is one service running on the internet: the collection of web pages viewed with a browser. When you load a page, the browser uses the URL to find the site, sends an HTTP request to the web server, and the server returns the page for the browser to display.

Security threats

Connected computers face attacks. See network security threats for the common ones.

• Unauthorised access: someone gaining entry to a system without permission.
• Interception: capturing data as it travels across a network (eavesdropping).
• Phishing: fake messages that trick a user into revealing personal data.
• Denial of service: flooding a system with traffic so it cannot serve legitimate users.

Protection measures

Defending a network needs several layers. See network protection measures for the measures and what each does.

• Strong passwords: long, hard-to-guess passwords that resist cracking.
• Firewalls: monitor and control traffic entering and leaving the network, blocking unwanted connections.
• Encryption: scrambles data so that even if it is intercepted it cannot be read without the key.
• Antivirus software: detects and removes malware.
• User access levels: limit each user to only the data and actions they need, reducing harm if an account is misused.

No single measure stops every threat, so these are combined as layers of defence.

How this module is examined

• Paper 1 (written, 60%). Define a network, LAN and WAN; explain IP addresses, protocols and packets; distinguish the internet from the web and describe how a page loads; and describe security threats and the protection measures that counter them.
• Match threats to measures. A common question pairs a threat with the measure that best defends against it, so learn them together.

Check your knowledge

Try these, then take the matching quiz for this module.

1. State the difference between a LAN and a WAN. (2 marks)
2. Define a protocol. (1 mark)
3. State the difference between the internet and the World Wide Web. (2 marks)
4. Name one protection measure against interception and explain how it helps. (2 marks)