Network Fundamentals
IB Syllabus: A2.1.1 – Purpose and characteristics of networks, A2.1.2 – Modern digital infrastructures, A2.1.3 – Network devices
Table of Contents
- Key Concepts
- Worked Examples
- Quick Check
- Trace Exercise
- Spot the Error
- Fill in the Blanks
- Predict the Output
- Practice Exercises
- Connections
Key Concepts
What is a Network? (A2.1.1)
A network is two or more computing devices connected together to share resources and communicate. Networks are the foundation of modern computing – from a student sharing a file with a classmate to billions of devices exchanging data across the internet.
The main purposes of a network are:
- Resource sharing – multiple devices can share hardware (printers, scanners), software (applications hosted on a server), and data (shared files and databases)
- Communication – users can exchange messages, video calls, and data in real time
- Data transfer – files and information can be moved between devices quickly and reliably
- Centralised management – an administrator can manage user accounts, security policies, software updates, and backups from a single location rather than configuring each device individually
Key characteristics used to evaluate and compare networks:
- Bandwidth – the maximum amount of data that can be transmitted per unit of time (e.g., 100 Mbps). Higher bandwidth means more data can flow simultaneously.
- Latency – the time delay between sending data and it arriving at its destination. Lower latency is better, especially for real-time applications like video calls and gaming.
- Reliability – how consistently the network maintains connections and delivers data without loss or corruption. Redundant paths and error-checking protocols improve reliability.
- Scalability – how easily the network can grow to accommodate more devices or increased traffic without significant performance degradation.
Network Types (A2.1.1)
Networks are classified by their geographic scope and purpose.
| Type | Scope | Examples | Key Features |
|---|---|---|---|
| LAN | Single building or campus | School computer lab, office network | High speed, limited area, owned by a single organisation |
| WAN | Large geographic area | The internet, a company linking offices across countries | Lower speed than LAN, wide coverage, often uses leased lines |
| PAN | Personal (a few metres) | Bluetooth headphones, smartwatch connected to a phone | Very short range, low power consumption |
| VPN | Virtual (over the internet) | Remote worker accessing the company network from home | Encrypted tunnel, user appears to be on the local network |
A VPN is not a physical network type – it is a virtual network that uses encryption to create a secure private connection over a public network (like the internet). This allows remote users to access a LAN as if they were physically connected to it. The “tunnel” means that all data travelling between the user and the LAN is encrypted, so even though it passes through the public internet, it cannot be read by anyone who intercepts it.
A common exam mistake is confusing LAN and WAN. Remember: LAN = Local (single building/campus, high speed, privately owned). WAN = Wide (large geographic area, connects multiple LANs, often uses third-party infrastructure).
Modern Digital Infrastructure (A2.1.2)
Modern computing relies on several interconnected infrastructure technologies. Each serves a different purpose and has distinct benefits and limitations.
The Internet – a global network of interconnected networks, all communicating using the TCP/IP protocol suite. The internet is the physical and logical infrastructure – cables, routers, servers, and protocols – that connects billions of devices worldwide.
The internet and the World Wide Web (WWW) are not the same thing. The internet is the underlying network infrastructure. The WWW is a service that runs on top of the internet – it is the collection of web pages accessed via web browsers using HTTP/HTTPS. Other services that run on the internet include email (SMTP), file transfer (FTP), and video streaming.
Cloud computing – the on-demand delivery of computing resources (storage, processing power, applications) over the internet. Organisations no longer need to buy and maintain their own servers – they rent resources from a cloud provider and pay only for what they use. See Cloud Computing for a detailed breakdown of IaaS, PaaS, and SaaS models.
Distributed systems – multiple computers working together, coordinated over a network, to appear as a single system to the user. The workload is shared across many machines, providing scalability and fault tolerance.
- Example: Google Search uses thousands of servers processing queries in parallel – if one server fails, others continue without interruption.
- Example: Cryptocurrency blockchains maintain a decentralised ledger across thousands of nodes worldwide. No single authority controls the system; transactions are verified by consensus among nodes.
Edge computing – processing data near the source (at the “edge” of the network) rather than sending it to a centralised data centre. This reduces latency because data does not need to travel long distances for processing.
- Example: Smart traffic lights process camera feeds locally to adjust signal timing in real time. Sending video to a data centre hundreds of kilometres away would introduce unacceptable delay.
- Example: Autonomous vehicles process sensor data on-board. A self-driving car cannot wait for a cloud server to decide whether to brake – the decision must happen in milliseconds.
Mobile networks – cellular networks (4G, 5G) that provide wireless internet access over wide geographic areas. Mobile networks use a system of base stations (cell towers) to relay signals between devices and the wider network. 5G offers significantly higher bandwidth and lower latency than 4G, enabling new applications like real-time remote surgery and augmented reality.
Benefits and Limitations of Modern Digital Infrastructure
| Benefit | Limitation |
|---|---|
| Resource sharing (printers, storage, internet access) | Security vulnerabilities (more entry points for attackers) |
| Global communication and collaboration | Dependency on infrastructure (ISP outages, cable damage) |
| Scalability (add resources on demand with cloud computing) | Cost of setup and ongoing maintenance |
| Redundancy and fault tolerance (distributed systems) | Privacy concerns (data in transit can be intercepted) |
| Centralised data management and backup | Complexity of management (more devices = more to configure and secure) |
Real-World Examples
- WWW – web browsers access web servers via HTTP/HTTPS over the internet. When you type a URL, your browser sends a request across the internet to a web server, which responds with the web page content.
- Cryptocurrency / blockchains – distributed systems where transactions are verified by a network of independent nodes, with no central authority. Each node holds a copy of the transaction ledger, making it extremely difficult to tamper with.
- Smart traffic lights – edge computing devices that use cameras and sensors to monitor real-time traffic flow and adjust signal timing locally, without needing to communicate with a distant server.
- School network – a LAN connecting computers, printers, and servers within a campus; managed centrally by IT staff; internet access provided via a WAN connection through the school’s ISP.
Network Devices (A2.1.3)
A network requires various hardware devices to connect, direct, and protect data as it travels between devices.
| Device | Function | Key Details |
|---|---|---|
| Gateway | Connects networks that use different protocols and translates between them | Acts as an entry/exit point for a network; often combined with a router in home networks |
| Hardware firewall | Inspects and filters network traffic based on security rules | Sits between the internal network and the internet; uses whitelists (allowed) and blacklists (blocked) to control traffic |
| Modem | Converts digital signals to analogue (and vice versa) for transmission over telephone or cable lines | MOdulator-DEModulator; required for broadband internet connections |
| Network Interface Card (NIC) | Provides the physical connection between a device and the network | Every networked device has one (wired or wireless); each NIC has a unique MAC address that identifies it on the local network |
| Router | Forwards data packets between different networks using IP addresses | Determines the best path for data; connects a LAN to a WAN (e.g., your home network to the internet) |
| Switch | Connects devices within the same network (LAN) and forwards data to the specific device using MAC addresses | More efficient than a hub – a hub sends data to all ports, while a switch sends only to the correct port |
| Wireless Access Point (WAP) | Provides wireless (Wi-Fi) connectivity to a wired network | Extends network coverage; devices connect wirelessly to the WAP, which is connected to the switch via a cable |
Router vs Switch: A switch operates within a network (connecting devices on the same LAN), while a router operates between networks (connecting your LAN to the internet/WAN). Think of a switch as a local postman delivering letters within your building, and a router as the postal service routing mail between cities.
Typical Network Layout
INTERNET
|
[Modem]
|
[Router] <-- Hardware Firewall
|
[Switch]
/ | \
PC1 PC2 [WAP]
/ \
Laptop Phone
In this layout:
- The modem converts the ISP’s signal for use by the home/school network
- The router directs traffic between the local network and the internet
- The hardware firewall (often built into the router) filters incoming and outgoing traffic
- The switch connects all wired devices on the LAN, forwarding data to the correct device using MAC addresses
- The WAP extends the network wirelessly so laptops and phones can connect without cables
- Every device (PC1, PC2, laptop, phone) has a NIC that provides its physical or wireless connection to the network
These devices operate at different layers of the TCP/IP model – we explore this in Protocols and Layers.
Standards and Protocols
This goes beyond the IB syllabus but helps build understanding.
Standards vs protocols: A standard is an agreed specification published by an official body (e.g., IEEE 802.11 defines the Wi-Fi standard), while a protocol is a set of rules for communication (e.g., HTTP defines how web browsers request and receive web pages). Standards are maintained by organisations like IEEE and ISO; protocols are implemented in software and hardware. A single standard may define multiple protocols. For example, the IEEE 802.11 standard defines protocols for wireless authentication, data framing, and error handling.
Worked Examples
Example 1: Choosing the Right Network Type
For each scenario, identify the most appropriate network type (LAN, WAN, PAN, or VPN) and explain your reasoning.
| # | Scenario | Network Type | Explanation |
|---|---|---|---|
| 1 | A student connects wireless earbuds to their phone via Bluetooth | PAN | Very short range (a few metres), connecting personal devices, uses Bluetooth |
| 2 | A multinational company connects offices in London, Tokyo, and New York | WAN | Spans a large geographic area across multiple countries |
| 3 | A teacher shares files with 30 computers in a classroom | LAN | Single room within a building, shared resources, high-speed connection |
| 4 | An employee works from home and securely accesses the company database | VPN | Creates a secure encrypted tunnel over the internet to access the private company LAN |
| 5 | Smart traffic lights at an intersection communicate with each other | LAN | Small geographic area (a single intersection), dedicated local network connecting the devices |
Example 2: Network Device Identification
For each scenario, identify which network device is primarily responsible and explain why.
| # | Scenario | Device | Explanation |
|---|---|---|---|
| 1 | Converting a broadband signal from the ISP for use by home devices | Modem | Converts the analogue ISP signal to digital signals that network devices can use |
| 2 | Directing a data packet from your home network to a web server in another country | Router | Forwards packets between different networks using IP addresses to find the best path |
| 3 | A laptop connects to the school network without a cable | Wireless Access Point | Provides Wi-Fi connectivity, bridging wireless devices to the wired LAN |
| 4 | Blocking an unauthorised connection attempt from the internet | Hardware firewall | Inspects incoming traffic and blocks connections that violate security rules |
| 5 | Sending data only to the specific computer that requested it, not to all computers on the network | Switch | Uses MAC addresses to forward data to the correct port rather than broadcasting to all ports |
Quick Check
Q1. Which type of network would connect Bluetooth earbuds to a smartphone?
Q2. What is the primary function of a router?
Q3. Which technology processes data near its source to reduce latency, rather than sending it to a centralised data centre?
Q4. What does a modem do?
Q5. A remote employee uses encrypted tunnelling to access their company's internal network from home. What type of network are they using?
Trace Exercise
A school has a computer lab, an admin office, and a library – each on a separate network segment. A student in the lab sends a print job to a printer in the admin office. Trace which network device handles each step of the process.
Trace: Printing Across Network Segments
A student in the computer lab sends a print request to a printer in the admin office. For each step, type the name of the network device responsible.
| Step | Action | Device |
|---|---|---|
| 1 | The student's computer sends the print request onto the network | |
| 2 | The request is forwarded to the correct port on the lab's local network | |
| 3 | The request crosses from the lab network to the admin office network | |
| 4 | The print data reaches the printer's network connection | |
| 5 | If the two networks use different protocols, translation occurs at the |
Spot the Error
A student wrote revision notes about network types. One line contains an error in the definition. Click the line with the error, then pick the correct fix.
Pick the correct fix for line 1:
Fill in the Blanks
Complete the summary of network devices by filling in the correct device name for each description.
Fill in the blanks to match each network device to its description:
NETWORK DEVICES
===============
A forwards packets between different networks using IP addresses.
A connects devices within the same LAN and forwards data using MAC addresses.
A converts digital signals to analogue for transmission over telephone lines.
A provides a device's physical connection to the network and has a unique MAC address.
A connects networks that use different protocols and translates between them.
Predict the Output
A school network has 3 computer labs, each on a separate subnet. A student in Lab A sends a file to a student in Lab C. The file must pass through at least one _____ to move between subnets.
Type the device name:
A home user has a modem, router, and switch. They connect a new desktop computer with an Ethernet cable. The computer connects to the _____ first.
Type the device name:
Practice Exercises
Core
-
Network Types – Define LAN, WAN, PAN, and VPN. For each, give one real-world example and explain why that network type is the most appropriate choice for your example.
-
Network Devices – Name and describe the function of five network devices. Draw a diagram showing where each device would be placed in a typical home network, and label each device with its function.
-
Digital Infrastructure – Explain the difference between the internet and the World Wide Web. Many people use these terms interchangeably – why is this incorrect?
Extension
- Edge vs Cloud – Compare edge computing and cloud computing. For each of the following scenarios, explain which approach would be more appropriate and why:
- (a) A self-driving car processing sensor data
- (b) A school storing student records
- (c) A factory monitoring equipment temperatures in real time
- VPN Analysis – Explain how a VPN works and why a company might require all remote employees to use one. Discuss both the security benefits and any potential drawbacks (e.g., reduced speed, cost, complexity of setup).
Challenge
- Infrastructure Design – A new international school is opening with two campuses 5 km apart. Each campus has 200 computers, shared printers, and a central server room. Students and teachers need to access the same resources from either campus, and some teachers will work from home. Design the network infrastructure, specifying:
- (a) The network type(s) needed and why
- (b) The devices required and where they would be placed (include a labelled diagram)
- (c) How remote access would be enabled for teachers working from home
- (d) What digital infrastructure services (cloud, edge, etc.) would benefit the school and why
Connections
- Prerequisites: Cloud Computing – cloud infrastructure builds on network connectivity; understanding IaaS/PaaS/SaaS helps explain how digital infrastructure is delivered over networks
- Prerequisites: OS Fundamentals – the OS manages NICs, the TCP/IP stack, and firewall rules that enable networking at the device level
- Related: Primary Memory – understanding cache and RAM helps explain how routers and switches buffer data packets during transmission
- Forward: Protocols and Layers – network devices operate at different layers of the TCP/IP model; protocols define the rules by which devices communicate
- Forward: Network Architecture – how networks are structured using topologies and models builds on the fundamentals covered here