Network Types
Key Definition
A network is a group of two or more computers or devices connected together to communicate and share resources such as files, printers, and internet connections.
Why Do We Need Networks?
Imagine a school where no one could talk to each other - chaos! Networks let computers "talk" to share:
- Files - like passing notes between friends
- Printers - one printer for everyone, not one each!
- Internet - one connection shared by all devices
LAN vs WAN
Networks are classified into two main types based on their geographical size:
The House vs City Analogy
LAN = Talking to people inside your house. You own the house, it's fast, and you're in control!
WAN = Phoning someone in another city. You use phone lines you don't own, and there's a delay!
LAN (Local Area Network)
- Covers a small geographical area (single building or site)
- Examples: school, office, home network
- Owned and maintained by the organisation
- Connected by cables (Ethernet) or Wi-Fi
- High data transfer speeds
- Low latency (fast response)
WAN (Wide Area Network)
- Covers a large geographical area (cities, countries, worldwide)
- Examples: internet, bank networks across branches
- Usually made up of multiple LANs connected together
- Uses telephone lines, fibre optic cables, satellites
- Third-party infrastructure (not owned by user)
- Higher latency than LANs
Key Fact
The Internet is the world's largest WAN - a global network of interconnected networks. It's basically millions of LANs all joined together!
Client-Server vs Peer-to-Peer
The Restaurant vs Potluck Analogy
Client-Server = A restaurant. One chef (server) cooks for everyone. Organised, but if the chef is sick, no one eats!
Peer-to-Peer = A potluck dinner. Everyone brings food to share. No single chef, but harder to organise!
Client-Server Network
- Central server provides services to clients
- Server manages files, security, backups
- Clients request resources from server
- Centralised management and control
- More secure and reliable
- Expensive (need dedicated server)
- Used in businesses and schools
Peer-to-Peer Network
- No central server
- All computers are equal (peers)
- Each computer can share and access files
- Decentralised - no single point of failure
- Less secure, harder to manage
- Cheap and easy to set up
- Used in small offices, homes
Wired vs Wireless Connections
| Aspect | Wired (Ethernet) | Wireless (Wi-Fi) |
|---|---|---|
| Speed | Faster (up to 10 Gbps) | Slower (typically up to 1 Gbps) |
| Reliability | More reliable, consistent connection | Subject to interference and signal loss |
| Security | More secure (physical access needed) | Less secure (signals can be intercepted) |
| Mobility | Fixed location, cables required | Freedom to move around |
| Cost | Expensive to install cables | Cheaper, no cabling needed |
Craig 'n' Dave: Types of Networks
LAN, WAN and network characteristics
Craig 'n' Dave: Wired and Wireless Networks
Performance comparison of different connection types
Craig 'n' Dave: Network Speeds
Understanding bandwidth and network performance
Past Paper Question
Q: Explain two differences between a LAN and a WAN. (4 marks)
Mark Scheme:
- A LAN covers a small geographical area/single site (1) whereas a WAN covers a large geographical area/multiple sites (1)
- A LAN is owned and maintained by the organisation (1) whereas a WAN uses third-party infrastructure/phone lines (1)
- A LAN typically has higher data transfer speeds (1) than a WAN (1)
Network Topologies
Key Definition
Network Topology is the arrangement or pattern in which nodes (devices) on a network are connected together. Think of it as the "shape" of your network!
Star
[PC]
|
[PC]--[HUB]--[PC]
|
[PC]
Like spokes on a wheel
Bus
[PC] [PC] [PC] [PC]
| | | |
=======================
(backbone cable)
Like a bus route
Mesh
[PC]----[PC] |\ /| | \ / | | \/ | | /\ | | / \ | [PC]----[PC]
Everyone connected!
Star Topology
Analogy: Like a spider web with the spider (hub/switch) in the middle. If one strand breaks, only one fly escapes - but if the spider dies, the whole web is useless!
All devices connect to a central hub or switch:
Advantages
- If one cable fails, only that device is affected
- Easy to add new devices
- Easier to manage and troubleshoot
- Good performance - no data collisions
Disadvantages
- If central hub/switch fails, whole network fails
- Requires more cable than bus topology
- More expensive (hub/switch needed)
Bus Topology
Analogy: Like a single road with houses along it. Everyone shares the same road, so if there's a traffic jam (collision), everyone waits. If the road is blocked, no one can travel!
All devices connect to a single central cable (backbone):
Advantages
- Simple and cheap to install
- Uses less cable than star topology
- Easy to add new devices
Disadvantages
- If backbone fails, whole network fails
- Data collisions reduce performance
- Harder to troubleshoot
- Limited cable length
- Security risk - all devices see all data
Mesh Topology
Analogy: Like a group of friends who ALL have each other's phone numbers. If one friend's phone breaks, you can still reach them through another friend. Super reliable, but lots of phone numbers to manage!
Every device connects directly to every other device:
Advantages
- Very reliable - multiple paths for data
- No single point of failure
- If one connection fails, data reroutes
- Good for critical systems
Disadvantages
- Very expensive - lots of cables/connections
- Complex to set up and manage
- Impractical for large networks
Which Topology is Best?
Star topology is the most common in modern LANs (schools, offices). Mesh topology is used in WANs and the internet where reliability is critical. Bus topology is rarely used today - it's outdated!
Craig 'n' Dave: Network Topologies
Star, bus, ring and mesh topologies explained
Past Paper Question
Q: A school is setting up a new computer room. Explain why star topology would be a better choice than bus topology. (4 marks)
Mark Scheme:
- In star topology, if one cable fails only that computer is affected (1)
- In bus topology, if the backbone fails the whole network fails (1)
- Star topology has better performance/no data collisions (1)
- Star topology is easier to add new computers (1)
- Star topology is easier to troubleshoot/identify faults (1)
Network Hardware
Key Definition
Network hardware refers to the physical devices needed to set up and operate a network. Each device has a specific job to help data travel from one place to another.
The Postal System Analogy
Think of a network like a postal delivery system:
- NIC = Your mailbox (lets you send/receive)
- Switch = Local post office (sorts mail for your street)
- Router = Main sorting office (decides which town to send mail to)
- WAP = A postman who delivers wirelessly (no postbox needed!)
Network Interface Card (NIC)
Hardware that allows a computer to connect to a network. Can be wired or wireless.
- Usually built into the motherboard
- Has a unique MAC address
- Converts data into signals for the network
Analogy: Your "ID badge" that lets you join the network party!
Switch
Connects devices together on a LAN. Sends data directly to the correct device.
- Reads MAC addresses to route data
- More efficient than a hub (sends to specific device, not all)
- Central point for star topology
Analogy: A smart receptionist who knows exactly which desk to deliver your message to!
Router
Connects different networks together (e.g., your LAN to the internet/WAN).
- Uses IP addresses to route data
- Finds the best path for data to travel
- Assigns IP addresses (DHCP)
- Often includes firewall protection
Analogy: A GPS that knows how to get your data to any address in the world!
Wireless Access Point (WAP)
Allows wireless devices to connect to a wired network using Wi-Fi.
- Creates a wireless local area network
- Bridges wireless and wired networks
- Often built into home routers
Analogy: A translator that lets wireless devices "speak" to the wired network!
What About Your Home "Router"?
The box in your home that you call a "router" is actually an all-in-one device! It's really a router + switch + wireless access point + modem all in one box. Clever, right?
Switch vs Hub - What's the Difference?
Switch (Smart)
Reads the destination address and sends data ONLY to that device. Efficient and secure!
Hub (Dumb)
Sends data to ALL devices and lets them figure it out. Wasteful, slow, and insecure - avoid!
Network Protocols
Key Definition
A protocol is a set of rules that governs how data is transmitted across a network. Protocols ensure that devices from different manufacturers can communicate with each other.
The Language Analogy
Protocols are like languages that computers agree to speak!
If you speak English and I speak French, we can't communicate. Protocols ensure ALL devices "speak the same language" so they can understand each other - even if they're made by different companies!
Why Do We Need Protocols?
Protocols define rules for:
- Data transmission speed - how fast data can be sent
- Error checking - detecting and correcting errors
- Addressing - how to locate devices on the network
- Data format - how data is structured
- Handshaking - establishing connections
Common Protocols
| Protocol | Full Name | Purpose |
|---|---|---|
| TCP/IP | Transmission Control Protocol / Internet Protocol | The foundation of internet communication. TCP breaks data into packets; IP addresses and routes them. |
| HTTP | Hypertext Transfer Protocol | Transfers web pages from servers to browsers. Used when you visit websites. |
| HTTPS | HTTP Secure | Secure version of HTTP. Encrypts data for safe transactions (banking, shopping). |
| FTP | File Transfer Protocol | Transfers files between computers across the internet. |
| SMTP | Simple Mail Transfer Protocol | Sends emails from client to server and between servers. |
| POP3/IMAP | Post Office Protocol / Internet Message Access Protocol | Retrieves emails from server to client. |
| Ethernet | - | Standard for wired LAN connections. Defines cable types and speeds. |
| Wi-Fi | - | Standard for wireless LAN connections. |
Layers of Protocols
Network communication uses layers, with each layer handling different tasks:
Application Layer
User-facing protocols: HTTP, HTTPS, FTP, SMTP, POP3
Transport Layer
TCP - ensures reliable delivery of data packets
Network Layer
IP - addresses and routes packets across networks
Link Layer
Ethernet, Wi-Fi - physical transmission of data
Craig 'n' Dave: Common Protocols
HTTP, HTTPS, FTP, SMTP and more
Craig 'n' Dave: TCP/IP Protocols
The foundation of internet communication
Past Paper Question
Q: Explain the difference between HTTP and HTTPS. (2 marks)
Mark Scheme:
- HTTPS encrypts data / HTTP does not (1)
- HTTPS is more secure / used for sensitive data like banking (1)
The Internet
Key Definition
The Internet is a global network of interconnected networks that use TCP/IP protocols to communicate. The World Wide Web is a service that runs on the internet, consisting of web pages accessed via browsers.
IP Addresses and MAC Addresses
The House Address vs Birth Certificate Analogy
IP Address = Your house address. It can change if you move house! It tells data WHERE to go on the network.
MAC Address = Your birth certificate. It NEVER changes - it's permanently attached to your network card!
IP Address
A unique numerical address that identifies each device on a network.
IPv4: 192.168.1.1IPv6: 2001:0db8:85a3:0000
- IPv4: 32-bit (4 billion addresses)
- IPv6: 128-bit (billions of billions!)
- Can change (dynamic) or stay fixed (static)
MAC Address
A unique hardware address burned into every network interface card.
00:1A:2B:3C:4D:5E
- 48-bit hexadecimal address
- Permanent - set by manufacturer
- Used for local network communication
- Also called "physical address"
Other Key Internet Concepts
| Concept | Description |
|---|---|
| DNS | Domain Name System - translates domain names (www.google.com) into IP addresses. Like a phonebook for the internet! |
| Router | Directs data packets between networks. Connects your LAN to the internet. |
| Switch | Connects devices within a LAN. Forwards data only to the intended device. |
| ISP | Internet Service Provider - company that provides internet access (e.g., BT, Virgin). |
Packet Switching
Data sent across the internet is broken into packets:
- Each packet contains a header (source IP, destination IP, packet number) and payload (the actual data)
- Packets can take different routes to reach the destination
- Packets are reassembled in order at the destination
- If packets are lost, they can be resent
- More efficient than circuit switching (phone calls)
How a Web Page is Loaded
User enters URL
User types www.example.com in the browser
DNS Lookup
Browser contacts DNS server to get IP address for the domain name
HTTP Request
Browser sends HTTP GET request to the web server
Server Response
Web server sends HTML, CSS, JavaScript files back in packets
Page Rendered
Browser reassembles packets and displays the web page
Craig 'n' Dave: How the Internet is Structured
Understanding how the internet works
Craig 'n' Dave: The Internet of Things
Connected devices and smart technology
Past Paper Question
Q: Describe the role of DNS when a user accesses a website. (3 marks)
Mark Scheme:
- DNS stands for Domain Name System (1)
- It translates the domain name/URL into an IP address (1)
- So the browser knows which server to connect to (1)
Network Security
Key Definition
Network Security involves protecting a network and its data from unauthorised access, misuse, modification, or denial of service. It includes both technical measures and policies.
Types of Malware
| Malware Type | Description |
|---|---|
| Virus | Malicious code that attaches to files and spreads when files are shared. Can delete or modify data. |
| Worm | Self-replicating malware that spreads across networks without user action. Often spreads via email. |
| Trojan | Malware disguised as legitimate software. Users are tricked into installing it. |
| Spyware | Secretly monitors user activity (websites visited, passwords) and sends data to hackers. |
| Ransomware | Encrypts user files and demands payment (ransom) to decrypt them. |
| Keylogger | Records keystrokes to capture passwords and sensitive information. |
Types of Cyber Attack
| Attack Type | Description |
|---|---|
| Phishing | Fake emails or websites that trick users into revealing personal information (passwords, bank details). |
| Brute Force | Trying every possible password combination until the correct one is found. |
| DDoS | Distributed Denial of Service - flooding a server with requests to make it unavailable. |
| SQL Injection | Inserting malicious SQL code into web forms to access or modify database data. |
| Man-in-the-Middle | Intercepting communication between two parties to steal or modify data. |
| Shoulder Surfing | Watching someone enter passwords or PINs by looking over their shoulder. |
Protection Methods
Technical Measures
- Firewall - monitors and filters network traffic
- Anti-malware - detects and removes malicious software
- Encryption - scrambles data so only authorised users can read it
- Software updates - patches security vulnerabilities
- Automatic backups - protects against data loss
User Measures
- Strong passwords - 8+ characters, mix of letters, numbers, symbols
- Two-factor authentication - extra verification step
- Access rights - limit who can access what data
- User training - recognising phishing and threats
- Acceptable use policy - rules for using the network
Encryption
Encryption converts readable data (plaintext) into unreadable data (ciphertext):
- Symmetric encryption: Same key used to encrypt and decrypt (e.g., AES)
- Asymmetric encryption: Different keys for encrypting (public) and decrypting (private)
- Used for: secure websites (HTTPS), email, stored files, VPNs
Key Fact
HTTPS uses SSL/TLS encryption to protect data sent between your browser and websites. The padlock icon shows a secure connection.
Craig 'n' Dave: Importance of Network Security
Why network security matters
Craig 'n' Dave: Identifying Network Vulnerabilities
Ways to find and understand security weaknesses
Craig 'n' Dave: Methods of Protecting Networks
Firewalls, encryption and other protection methods
Craig 'n' Dave: Malware
Viruses, worms, trojans and other malicious software
Craig 'n' Dave: How Hackers Exploit Technical Vulnerabilities
Understanding common attack methods
Craig 'n' Dave: Social Engineering
Phishing, pretexting and human-based attacks
Craig 'n' Dave: Protecting Digital Systems and Data
Security measures and best practices
Past Paper Question
Q: Describe two methods an organisation could use to protect their network from cyber attacks. (4 marks)
Mark Scheme:
- Firewall: Monitors incoming and outgoing network traffic (1) and blocks unauthorised access/suspicious activity (1)
- Anti-malware software: Scans files for known malware/viruses (1) and removes or quarantines infected files (1)
- Encryption: Scrambles data so it cannot be read (1) if intercepted by hackers (1)
- Strong passwords: Complex passwords are harder to guess/crack (1) reducing risk of unauthorised access (1)
Topic 4 Quiz
Test Your Knowledge
Complete this 15-question quiz to test your understanding of networks, protocols, and security. You'll receive a PDF certificate with your results.