Unit 1: Digital Technology – Network Technologies Study Notes
Welcome to your study guide for Network Technologies! Whether you are already a tech enthusiast or someone who finds computer systems a bit intimidating, do not worry—this guide breaks down everything step-by-step using plain English, clear real-world examples, and helpful memory tricks.
In this unit, we explore how computers talk to one another, share files, connect to the internet, and keep data safe from cyber threats.
---1. What is a Computer Network?
A computer network is simply two or more computing devices connected together using communication media (such as cables or Wi-Fi) so they can share data, hardware, and software.
Think of a computer network like a road system connecting houses. Without roads, every house is isolated. With roads, people can visit each other, share tools, and send letters back and forth.
Advantages of Networking
• Resource Sharing: Multiple computers can share one piece of expensive hardware, such as a printer or scanner.
• Centralised File Sharing: Users can access their files from any computer on the network.
• Centralised Backups: Network administrators can back up everyone's work in one single operation.
• Centralised Software Deployment: Updates and software can be installed across all computers at once rather than going to each machine individually.
• Communication: Users can communicate instantly via email, messaging, and shared calendars.
Disadvantages of Networking
• Security Risks: If a hacker or virus gets into the network, all connected computers are vulnerable.
• Network Failure: If a main server or switch fails, many users may not be able to do their work.
• Initial Setup Cost: Buying cables, switches, servers, and paying specialists to install them can be expensive.
• Maintenance: Networks often require trained staff (network managers/administrators) to run smoothly.
Quick Review: Networks save money and time through sharing and central management, but they introduce security risks and maintenance costs.
---2. Types of Networks by Geographic Scale
Networks are categorised by how much physical space they cover. Here are the four main types you need to know for your exam:
1. LAN (Local Area Network)
• Coverage: A small geographical area, such as a single room, building, school, or office.
• Ownership: The network hardware and cables are usually owned and maintained by the organisation using it.
• Example: Your school computer room or your home Wi-Fi network.
2. WAN (Wide Area Network)
• Coverage: A large geographical area connecting cities, countries, or the entire globe.
• Ownership: Uses telecommunication links and infrastructure owned by external third parties (like British Telecom or Virgin Media).
• Example: The Internet is the ultimate example of a WAN.
3. PAN (Personal Area Network)
• Coverage: Centred around an individual person, typically within a range of \(10\text{ metres}\).
• Technology: Usually connects devices wirelessly using Bluetooth.
• Example: Connecting your smartphone to wireless earbuds or a smartwatch.
4. WLAN (Wireless Local Area Network)
• Coverage: Same as a LAN, but uses wireless signals (radio waves / Wi-Fi) instead of physical cables to connect devices.
• Example: Your home network when you connect a tablet or laptop to your broadband router without plugging in an Ethernet cable.
Memory Trick: Think of size from smallest to largest: PAN (Personal/Pocket) \(\rightarrow\) LAN/WLAN (Local building) \(\rightarrow\) WAN (Worldwide).
---3. Network Models: Client-Server vs Peer-to-Peer
Computers on a network can be organised in two main ways: Client-Server and Peer-to-Peer (P2P).
Client-Server Network
In this model, one powerful central computer (the server) provides services and stores files, while other computers (the clients) request resources from it.
Analogy: Think of a restaurant. The waiter/kitchen is the server and the customers are the clients. You ask the server for food; the server delivers it to you.
• Advantages: Files and security are managed centrally; backups can be scheduled automatically on the server; clients can log in from any computer.
• Disadvantages: If the server crashes, nobody can access their central files; servers are expensive to purchase and require specialist IT managers.
Peer-to-Peer (P2P) Network
In a P2P network, there is no central server. Every computer (called a peer) has equal status and can act as both a client and a server.
Analogy: A group project with your friends where everyone holds their own notes and shares directly with each other without a teacher directing them.
• Advantages: Cheap and simple to set up; if one computer fails, the rest of the network keeps working; no need for expensive server hardware.
• Disadvantages: No central backup (each user must back up their own files); security is managed on each individual machine; files can be scattered across different devices, making them harder to find.
Common Exam Trap: Do not confuse a client-server network with the internet. While websites use servers, the client-server concept also applies to a simple school computer lab!
---4. Network Topologies
A topology is the physical or logical layout of how computers and cables are arranged in a network.
1. Star Topology
• Structure: Every device is connected directly to a central node (a switch or hub).
• Advantages: If one cable breaks, only that single device goes offline—the rest of the network continues working normally. It is also very easy to add new devices without disrupting others.
• Disadvantages: If the central switch fails, the entire network goes down. It requires a lot of cabling compared to a bus topology.
2. Bus Topology
• Structure: All devices share a single main cable called the backbone. Terminators are placed at each end to stop signals bouncing back.
• Advantages: Very cheap and easy to install because it uses minimal cabling.
• Disadvantages: If the main backbone cable breaks, the entire network fails. As more devices are added, data collisions increase, slowing down performance.
3. Ring Topology
• Structure: Devices are connected in a continuous loop. Data travels in one direction around the ring from computer to computer.
• Advantages: Data collisions are avoided because data moves in a single direction in a predictable sequence.
• Disadvantages: If any single computer or cable breaks, the whole ring is broken and the entire network goes down. Adding or removing computers temporarily shuts down the network.
4. Mesh Topology
• Structure: Devices are interconnected so that there are multiple paths between any two points.
• Advantages: Extremely reliable and robust. If one path or device fails, data simply travels down another route (called self-healing).
• Disadvantages: In a full wired mesh, the amount of cabling and cost is very high and complex to install.
Key Takeaway: The Star topology is the most common in modern schools and businesses because a single cable fault does not take down the whole system.
---5. Network Hardware
To connect computers together and send data across the world, specific hardware devices are required:
Network Interface Card (NIC)
• A hardware component (built into the motherboard or plugged in via USB) that allows a device to connect to a network.
• Every NIC has a unique physical hardware address called a MAC Address hardcoded into it at manufacture.
Hub vs Switch
• Hub: A simple device that receives a data packet and broadcasts it to every port on the network. This creates unnecessary network traffic and reduces security.
• Switch: A smart device that inspects the destination MAC address of incoming data and sends the packet only to the specific device it is meant for. This reduces network traffic and speeds up data delivery.
Router
• A device that connects different networks together (for example, connecting your home LAN to the internet WAN).
• Routers read IP addresses to determine the fastest route for data packets across the internet.
Wireless Access Point (WAP)
• A device that receives wired data from a switch/router and broadcasts it as wireless radio signals (Wi-Fi), allowing wireless devices to connect to a wired network.
---6. Transmission Media (Cables & Wireless)
Data must travel through a physical medium. Let us compare the three main options:
1. Unshielded Twisted Pair (UTP / Copper Ethernet Cable)
• Transmits data using electrical pulses.
• Pros: Inexpensive, flexible, easy to install.
• Cons: Limited range (up to \(100\text{ metres}\) before signal degrades), vulnerable to electrical interference.
2. Fibre Optic Cable
• Transmits data using pulses of light through thin glass or plastic strands.
• Pros: Extremely fast data transfer, travels long distances without signal loss, immune to electrical interference.
• Cons: Expensive to buy and requires specialist tools and training to install.
3. Wireless (Wi-Fi / Radio Waves)
• Transmits data using radio frequencies.
• Pros: User mobility, no messy cables, easy to connect new mobile devices.
• Cons: Lower speeds than wired cables, signal can be blocked by thick walls, vulnerable to interception if not encrypted.
7. Addressing: MAC vs IP Addresses
Every device needs an address so data finds the right destination.
MAC Address (Media Access Control)
• What is it? A unique identifier permanently burned into the device's NIC during manufacturing.
• Format: 48-bit hexadecimal number, e.g., \(00\text{:}1A\text{:}2B\text{:}3C\text{:}4D\text{:}5E\).
• Analogy: Your fingerprint or DNA—it never changes, no matter where you travel in the world.
IP Address (Internet Protocol)
• What is it? A logical address assigned to a device by the network it is currently connected to.
• Format: IPv4 uses four 8-bit numbers separated by dots, e.g., \(192.168.1.1\).
• Analogy: Your postal address—it changes whenever you move to a new house or connect to a new Wi-Fi hotspot.
8. Network Protocols
A protocol is an agreed set of standard rules that determines how devices communicate and format data across a network. Without protocols, devices made by different manufacturers could not understand each other.
Essential Protocols to Memorise
• TCP/IP (Transmission Control Protocol / Internet Protocol): The fundamental protocol suite of the internet. TCP breaks data down into smaller packets and reassembles them at the destination; IP handles routing the packets to the correct address.
• HTTP (HyperText Transfer Protocol): Used by web browsers to request and display web pages from web servers.
• HTTPS (HTTP Secure): An encrypted version of HTTP that protects sensitive data (like passwords and credit card details) from eavesdropping.
• FTP (File Transfer Protocol): Used specifically for uploading and downloading files between a client and a remote server.
• SMTP (Simple Mail Transfer Protocol): Used for sending emails from a client to a server or between servers.
• POP3 (Post Office Protocol): Downloads emails from a server to a local device and deletes them from the server.
• IMAP (Internet Message Access Protocol): Syncs emails with the mail server so you can view the same inbox across multiple devices (phone, laptop, tablet).
Memory Trick for Email Protocols:
• SMTP = Send My Texts Please (Sending mail)
• POP = Pulls emails Off the server permanently
• IMAP = Identical across Multiple Apps/devices
9. Network Security Essentials
Protecting networks from unauthorised access and cyber threats is critical.
1. Firewalls
• Hardware or software that monitors incoming and outgoing traffic based on security rules.
• Blocks unauthorised incoming connections and prevents malware from sending data out.
2. Encryption
• Scrambles plain text into unreadable ciphertext using an algorithm and a key.
• If intercepted, the data cannot be understood without the decryption key (e.g., HTTPS, WPA2/WPA3 Wi-Fi passwords).
3. User Access Levels & Authentication
• Authentication: Proving who you are using passwords, PINs, biometrics (fingerprint/facial scan), or two-factor authentication (2FA).
• Access Levels: Restricting what users can see and do based on their role. For example, in a school, students can read resources, but only teachers can view gradebooks, and only network managers can install software.
Summary Checklist
Before moving on to the next topic, check that you can:
• Define a computer network and state two pros and two cons.
• Distinguish between LAN, WAN, PAN, and WLAN.
• Explain the differences between Client-Server and Peer-to-Peer networks.
• Compare Star, Bus, Ring, and Mesh topologies.
• State the purpose of a Switch, Router, NIC, and WAP.
• Distinguish between a MAC address (permanent/hardware) and an IP address (logical/network).
• State the function of common protocols (HTTP, HTTPS, FTP, SMTP, POP, IMAP).
• Explain how firewalls, encryption, and access levels protect network data.