What You'll Learn
- Types of networks: LAN and WAN
- Factors that affect network performance
- Client-server vs peer-to-peer networks
- Network hardware: routers, switches, NICs, and more
- The Internet, DNS, and the Cloud
- Star and Mesh network topologies
1. Types of Networks
What is a Network?
A computer network is two or more computers connected together to share resources (files, printers, internet) and communicate with each other.
LAN - Local Area Network
Definition: A network covering a small geographical area, typically a single building or site.
Characteristics:
- Covers a small area (room, building, campus)
- Usually owned and managed by one organisation
- High-speed connections (typically 100 Mbps - 10 Gbps)
- Lower cost to set up and maintain
- Uses private infrastructure
Common Examples:
- School computer network
- Home WiFi network
- Office network in one building
- Internet cafe
WAN - Wide Area Network
Definition: A network covering a large geographical area, connecting multiple LANs across cities, countries, or continents.
Characteristics:
- Covers a large area (cities, countries, worldwide)
- Often uses third-party telecommunications
- Generally slower than LAN (depends on connection)
- Higher cost due to infrastructure
- Uses public or leased infrastructure
Common Examples:
- The Internet (largest WAN)
- Bank networks connecting branches
- Company network linking offices worldwide
- Government networks
Key Difference
LAN = Small area, owned by you, fast, cheap
WAN = Large area, uses external providers, can be slower, more expensive
2. Factors Affecting Network Performance
Several factors determine how fast and reliably a network operates:
Bandwidth
What it is: The maximum amount of data that can be transmitted per second, measured in bits per second (bps, Mbps, Gbps).
Effect: Higher bandwidth = faster potential speeds. Like a wider pipe allowing more water to flow.
Number of Devices
What it is: How many computers, phones, and other devices are using the network simultaneously.
Effect: More devices = bandwidth shared between them = slower speeds for each user.
Transmission Media
What it is: The physical medium used to carry data (cables or wireless signals).
Effect: Different media have different speeds and reliability.
Fibre optic: Fastest, most reliable, expensive
Ethernet cable: Fast, reliable, affordable
WiFi: Convenient, slower, affected by interference
Network Traffic
What it is: The amount of data currently being transmitted across the network.
Effect: High traffic during peak times causes congestion and slower speeds.
Latency
What it is: The delay between sending data and it arriving at its destination.
Effect: High latency causes lag in games and video calls, even with fast bandwidth.
Errors & Interference
What it is: Data corruption or signal interference requiring retransmission.
Effect: Data must be resent, slowing overall transmission.
3. Network Models: Client-Server vs Peer-to-Peer
Client-Server Network
How it works:
- One or more powerful servers provide services
- Clients (user computers) request services
- Server manages all shared resources centrally
Server Types:
- File server: Stores and shares files
- Web server: Hosts websites and web pages
- Print server: Manages shared printers
- Email server: Handles email sending/receiving
- Database server: Stores and manages data
Advantages:
- Centralised security and backup
- Easier to manage and update
- Better security controls
- More scalable for large networks
Disadvantages:
- Expensive server hardware required
- Needs specialist IT staff
- If server fails, services stop
- Server can become a bottleneck
Peer-to-Peer (P2P) Network
How it works:
- All computers are equal (peers)
- Each computer can be both client AND server
- Resources shared directly between computers
Common Uses:
- Small home/office networks
- File sharing applications
- Cryptocurrency networks (Bitcoin)
- Some online gaming
Advantages:
- No expensive server needed
- Easy to set up
- No single point of failure
- Each user controls their own computer
Disadvantages:
- Harder to secure
- No centralised backup
- Difficult to manage when network grows
- Each computer must be individually maintained
4. Network Hardware
These devices are needed to connect computers into a LAN:
NIC (Network Interface Card)
What it does: Allows a computer to connect to a network. Converts data into signals for transmission.
Types:
- Wired NIC: Ethernet port (RJ45 connector)
- Wireless NIC: WiFi adapter
Location: Built into motherboard or added as expansion card/USB adapter.
Key fact: Every NIC has a unique MAC address for identification.
Switch
What it does: Connects multiple devices within a LAN. Sends data only to the intended recipient device.
How it works:
- Learns MAC addresses of connected devices
- Creates direct connection between sender and receiver
- More efficient than a hub (which broadcasts to all)
Location: Central point in a LAN, often in server room or network cabinet.
Router
What it does: Connects different networks together (e.g., LAN to the Internet). Directs data packets to their destination.
How it works:
- Uses IP addresses to route data
- Finds the best path for data to travel
- Acts as gateway between networks
Home routers: Often combine router + switch + wireless access point in one device.
Wireless Access Point (WAP)
What it does: Allows wireless devices to connect to a wired network using WiFi.
How it works:
- Converts wired signal to wireless (and vice versa)
- Broadcasts SSID (network name)
- Handles wireless security (WPA2, WPA3)
Range: Typically 30-50 metres indoors, affected by walls and interference.
Transmission Media
What it is: The physical cables or wireless signals that carry data.
| Type | Speed | Use |
|---|---|---|
| Ethernet (Cat5e/Cat6) | 1-10 Gbps | Office/home networks |
| Fibre Optic | 10-100+ Gbps | Backbone, data centres |
| WiFi (802.11ac/ax) | Up to 10 Gbps | Wireless devices |
5. The Internet
What is the Internet?
The Internet is a worldwide collection of interconnected computer networks - a "network of networks". It connects millions of private, public, academic, business, and government networks.
DNS - Domain Name System
You type: www.google.com
DNS Server looks up the name
Returns IP: 142.250.187.46
Browser connects to that IP address
What it does: Translates human-readable domain names (URLs) into IP addresses that computers use.
Why needed: Humans remember names easily; computers use numbers.
Key fact: The DNS is made up of multiple DNS servers distributed worldwide, working together hierarchically.
Web Servers and Clients
Client
(Your browser)
Requests web page
Web Server
(Hosts website)
Sends HTML, images, etc.
Web Server: A computer that stores website files and serves them to clients on request.
Client: A program (like a web browser) that requests and displays content from servers.
Hosting
What it is: Storing website files on a web server so they're accessible via the Internet 24/7.
Types:
- Shared hosting: Multiple websites on one server (cheapest)
- Dedicated hosting: Your own server (expensive)
- Cloud hosting: Distributed across multiple servers
The Cloud
What it is: Remote servers accessed via the Internet that provide storage, software, and processing power.
Storage
Google Drive, Dropbox, iCloud
Software
Google Docs, Office 365, Photoshop
Processing
AWS, Azure, game streaming
Advantages
- Access files from anywhere
- Automatic backups
- No need for expensive hardware
- Easy collaboration
- Scales up/down as needed
- Provider handles maintenance
Disadvantages
- Requires Internet connection
- Ongoing subscription costs
- Data security concerns
- Less control over your data
- Dependent on provider's reliability
- Privacy concerns
6. Network Topologies
A network topology is the arrangement of devices and connections in a network. It affects performance, reliability, and cost.
Star Topology
Structure: All devices connect to a central switch or hub.
Advantages
- Easy to add new devices
- If one cable fails, only that device is affected
- Easy to troubleshoot problems
- Good performance - no data collisions
- Centralised management
Disadvantages
- If central switch fails, whole network fails
- Requires more cable than bus topology
- Central switch is a single point of failure
- Can be expensive for large networks
Common use: Most modern LANs, offices, schools
Mesh Topology
Structure: Every device connects to every other device (full mesh) or to several others (partial mesh).
Advantages
- Very reliable - many redundant paths
- No single point of failure
- Data can take alternative routes if one fails
- Good for critical systems
- Can handle high traffic
Disadvantages
- Very expensive - lots of cabling/connections
- Complex to set up and manage
- Difficult to troubleshoot
- Each device needs multiple NICs
- Not practical for large networks
Common use: Internet backbone, military networks, critical infrastructure
Quick Comparison
| Factor | Star | Mesh |
|---|---|---|
| Cost | Moderate | High |
| Reliability | Central point of failure | Very high (redundant paths) |
| Complexity | Simple | Complex |
| Scalability | Easy to expand | Difficult to expand |
| Best for | Offices, schools, homes | Critical systems, Internet backbone |
Summary
Network Types
LAN: Local, fast, cheap, single site
WAN: Wide area, connects LANs, Internet
Performance Factors
Bandwidth, number of devices, transmission media, traffic, latency, errors
Network Models
Client-Server: Centralised, managed, scalable
P2P: Decentralised, simple, equal peers
Hardware
NIC, Switch, Router, WAP, Transmission media
Internet Concepts
DNS (URL → IP), Web servers/clients, Hosting, The Cloud
Topologies
Star: Central hub, easy to manage
Mesh: All connected, very reliable
Practice Activities
Predict
Can you predict which network type, topology, or hardware is needed?
Worked Examples
See step-by-step solutions to network scenarios.
Trace
Follow data through networks and understand each step.
Parsons Problems
Put the steps in the correct order.
Knowledge Quiz
Test your understanding with 15 questions.