📱 Devices on a Network

• Desktop computers and laptops
• Mobile phones and tablets
• Games consoles and smart TVs
• Servers, printers and routers

If a device can send or receive data, it can be part of a network.

📡 Why Networks Are Useful

• Share files between users
• Share hardware (e.g. printers)
• Share one internet connection
• Communicate quickly using email or messaging

🏫 Real-World Examples

• Schools – shared student files and printers
• Homes – multiple devices sharing Wi-Fi
• Businesses – shared servers and databases

📜 What Is a Protocol?

• A protocol is a set of rules for communication
• Rules decide how data is:
• Sent
• Received
• Checked for errors

🗣️ Protocols in Everyday Life

• Saying “hello” before speaking
• Taking turns in conversation
• Using agreed greetings in different cultures

Computers also need agreed rules to avoid confusion.

💻 Why Computer Protocols Matter

• Different devices can work together
• Manufacturers follow the same standards
• Data arrives in the correct format
• Errors can be detected and fixed

📧 Email Protocols

• SMTP – Simple Mail Transfer Protocol
• Used to send emails from one server to another
• IMAP – Internet Message Access Protocol
• Used to access emails from different devices

🌐 Web Protocols

• HTTP – loads web pages
• Data is sent in plain text
• HTTPS – secure version of HTTP
• Uses encryption to protect data

🔐 Why HTTPS Is Important

• Prevents data being read if intercepted
• Protects passwords and personal information
• Used for online banking and shopping

🧠 Exam Tip

• Always link protocols to rules
• Explain why they are needed, not just what they are
• Use examples (email, web browsing)

🔌 Ethernet (Cat 5) Cables

• Ethernet cables are used in wired networks
• Made from twisted pairs of copper wires
• Twisting reduces electromagnetic interference

⚡ How Ethernet Cables Transmit Data

• Data is transmitted as electrical signals
• Signals travel both directions along the cable
• Provides a stable and reliable connection

✅ Advantages of Ethernet

• Faster than most wireless connections
• Less affected by interference
• More secure than wireless

❌ Disadvantages of Ethernet

• Requires lots of cables
• Cables can be expensive to install
• Devices are fixed in place

🔀 What Is a Switch?

• A switch connects multiple devices on a local area network (LAN)
• Each device plugs into the switch using an Ethernet cable

🧠 How a Switch Works

• Each device has a unique MAC address
• The switch learns which MAC address is on each port
• Data is sent only to the correct device

🚦 Why Switches Are Efficient

• Reduces unnecessary network traffic
• Improves performance
• Prevents data collisions

🗄️ What Is a File Server?

• A server is a powerful computer on a network
• A file server stores users’ files centrally
• Users can log in from any computer

📁 Benefits of File Servers

• Files are not lost if one computer fails
• Easy to back up data
• Supports shared folders

🌍 What Is a Router?

• A router connects different networks together
• Most commonly connects a LAN to the internet
• Acts as a gateway

📡 How Routers Route Data

• Routers read the destination IP address
• Forward data towards the correct network
• Ignore data not meant for their network

🏢 Real-World Example

• School computers connect to a switch
• The switch connects to a file server
• The router connects the school to the internet

🧠 Exam-Style Language

• “A switch improves network efficiency by…”
• “A file server benefits users because…”
• “A router is required when…”

📝 Exam Tip

• Always link hardware → function → benefit
• Avoid just listing devices
• Explain why each device is used

🧱 The Internet Is Physical

• The internet is not “the cloud”
• It is made of physical hardware
• This includes cables, routers, switches and servers

💻 Devices on the Internet

• Laptops and desktop computers
• Mobile phones and tablets
• Games consoles and smart TVs
• Servers in data centres

Any device connected to the internet becomes part of it.

🌊 How Data Travels Long Distances

• Most internet data travels through cables
• These cables run:
• Underground
• Under streets
• Across the ocean floor

🌍 Undersea (Submarine) Cables

• Carry over 99% of internet data
• Stretch thousands of kilometres
• Connect continents together

⚠️ Risks to Undersea Cables

• Damaged by ship anchors
• Damaged by fishing nets
• Rarely damaged by wildlife

Damage can slow or disrupt internet access between countries.

📡 What Do We Use the Internet For?

• Communication (email, messaging, video calls)
• Entertainment (streaming, gaming)
• Online shopping and banking
• Social media and research

📦 How Information Is Sent

• Messages are not sent in one piece
• They are split into packets
• Packets can take different routes

🧾 What Each Packet Contains

• Sender IP address
• Receiver IP address
• Sequence number
• Payload (the data)

🔁 Why Packets Are Used

• Makes data transfer more reliable
• Reduces congestion on the network
• Allows rerouting if one path fails

🏷️ IP Addresses

• An IP address uniquely identifies a device
• Written as four numbers (0–255)
• Example: 192.168.1.10

🔐 IP Addresses & Security

• IP addresses can reveal:
• Approximate location
• Internet Service Provider (ISP)
• This is why security and privacy matter

🚦 Role of Routers on the Internet

• Routers read destination IP addresses
• They forward packets towards the correct network
• Packets may pass through many routers

🌐 Internet vs World Wide Web

• The internet is the infrastructure
• The World Wide Web is a service that runs on it
• The web uses browsers, servers and HTTP/HTTPS

🧠 Exam-Style Language

• “The internet is a worldwide network of networks…”
• “Data is split into packets to improve reliability…”
• “Routers forward packets based on IP addresses…”

📝 Exam Tip

• Do not describe the internet as “websites”
• Mention hardware and packets
• Use the phrase physical infrastructure

⚠️ Internet vs World Wide Web

• The internet = physical infrastructure (cables, routers, servers)
• The World Wide Web = websites and web pages
• The web could not exist without the internet

💻 What Is a Web Client?

• A web client is the user’s device
• Examples: laptop, phone, tablet
• The client requests web pages from servers

🌍 What Is a Web Browser?

• A browser is software used to access the web
• It sends requests on behalf of the client
• It displays web pages to the user

Examples: Chrome, Edge, Firefox, Safari

🖥️ What Is a Web Server?

• A web server is a powerful computer
• It stores website files (HTML, images, CSS)
• It responds to requests from clients

🔁 The Client–Server Model

• The client requests a web page
• The server responds with the requested data
• This process happens every time a page loads

📄 What Is a Website?

• A website is a collection of related web pages
• Web pages are written in HTML
• CSS controls how pages look

🔗 What Is a URL?

• A URL identifies the location of a resource on the web
• It tells the browser where to go
• Each website has a unique URL

🧩 Parts of a URL

• Protocol – how data is transferred (http / https)
• Domain name – the website name
• Path – specific page or resource

https://www.bbc.co.uk/news

📘 What Is a Domain Name?

• A domain name is a human-readable website address
• Much easier to remember than IP addresses
• Each domain name is unique

📇 Top-Level Domains (TLDs)

• .com – commercial organisations
• .org – organisations
• .co.uk – UK businesses

🔄 What Is DNS?

• DNS stands for Domain Name System
• It converts domain names into IP addresses
• This allows browsers to find the correct server

🧠 Why DNS Is Important

• Humans remember names, not numbers
• DNS removes the need to memorise IP addresses
• Makes the web easy to use

🔐 HTTP vs HTTPS

• HTTP sends data in plain text
• HTTPS uses encryption
• HTTPS protects data during transfer

🔑 Encryption on the Web

• Uses public and private keys
• Prevents attackers reading intercepted data
• Essential for passwords and payments

🧠 Exam-Style Language

• “The World Wide Web is a service that runs on the internet…”
• “A browser acts as a client requesting data…”
• “DNS converts domain names into IP addresses…”

📝 Exam Tip

• Do not confuse the web with the internet
• Always mention the client–server model
• Include DNS when explaining URLs