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The Standalone Computer
A standalone computer operates entirely on its own — not connected to any other device. It has its own operating system, software, and local storage. Every user works in isolation.
- Simple — no extra hardware needed
- Secure: no network attack surface
- No dependency on a server
- Faster for isolated local tasks
- Files shared only via USB or physical media
- Each machine needs its own printer
- Software installed per machine — costly
- No central backups; data lost if drive fails
- No communication between users
Why Connect Computers?
As organisations grew, buying a printer per machine and physically carrying files on USB drives became impractical and expensive. Networking solves this: connect computers and let them share resources and communicate instantly.
- One printer shared across all PCs
- Site licence software — cheaper per seat
- Central file storage — any machine, any time
- Email and instant messaging
- Remote software updates by admin
- Extra hardware: switch, cables, NICs
- Server failure affects everyone
- Viruses spread to all machines
- Needs a network administrator
Local Area Network (LAN)
A LAN connects computers within a limited geographical area — a classroom, office floor, or building. It is typically owned and managed by the organisation itself using its own cabling and switches. Your school network is a LAN.
- Very fast data transfer — short cable runs
- Organisation owns and controls all hardware
- Share printers, scanners, file servers
- Centralised software updates and security
- Limited to one site — cannot span cities
- Physical cabling expensive to install
- Requires staff with networking expertise
- Switch failure affects all connected devices
Network Topologies
A topology describes how devices are physically arranged and connected on a network. The choice affects speed, cost, and reliability. The star topology is by far the most common in schools and offices.
Star Topology
- Fast — minimal collisions
- Easy to add new devices
- One device failing doesn’t affect others
- Easy to identify faults
- Switch failure = entire network down
- Requires extra hardware (switch)
- More cable needed than bus
Bus Topology
- Easy to set up
- Uses less cable than star
- If the backbone cable fails the whole network goes down
- Performance degrades with more devices
- Difficult to troubleshoot
- Data collisions common
Ring Topology
- Data flows in one direction reducing collisions
- Performs better than bus under heavy load
- If one device or cable fails the whole network goes down
- Difficult to add new devices (must break the ring)
- Slower as data passes through every device
Client–Server Model
Most school and business networks use the client–server model: a powerful server manages shared resources, user accounts, and security policies. Each user’s PC is a client that sends requests to the server and receives responses.
- Centralised security and access control
- Easy to back up all data centrally
- Admin updates software remotely
- Server scales to handle many clients
- Expensive to buy and maintain a server
- Server failure = all clients lose access
- Needs skilled network administrator
Peer-to-Peer Networks
In a peer-to-peer (P2P) network, every computer is equal — there is no central server. Each device can share files, printers, and other resources directly with every other device. This is commonly used in small home networks or for file-sharing applications.
- No server needed — cheaper to set up
- Easy to configure for small networks
- No single point of failure (no server to crash)
- Each PC controls its own files and security
- No central security — each PC manages its own
- Harder to manage as network grows
- Files spread across multiple machines — hard to find and back up
- Performance slows as more devices share resources
Exam tip: You must be able to compare client-server and peer-to-peer networks. Client-server uses a central server for management and security; peer-to-peer has no server and every device is equal. Client-server is used in schools and businesses; P2P is used in small home networks.
Wired vs Wireless Connections
Networks can use wired connections (such as Ethernet cables) or wireless connections (such as WiFi or Bluetooth). Most networks use a combination of both. Understanding the trade-offs between wired and wireless is essential for GCSE.
| Feature | Wired (Ethernet) | Wireless (WiFi / Bluetooth) |
|---|---|---|
| Speed | Faster — dedicated cable per device | Slower — shared radio frequency |
| Reliability | Very reliable — no interference | Less reliable — walls, interference, distance |
| Security | More secure — physical access needed | Less secure — signals can be intercepted |
| Flexibility | Less flexible — devices tied to cable location | Very flexible — connect anywhere in range |
| Cost | Expensive to install cables in walls/floors | Cheaper — just needs a WAP |
| Adding devices | Needs a free port on the switch | Easy — just connect to the WiFi |
Key terms: A NIC (Network Interface Card) is the hardware inside a device that allows it to connect to a network — either wired (Ethernet port) or wireless (WiFi antenna). A WAP (Wireless Access Point) is a device that creates a wireless network, allowing devices to connect via WiFi.
Wide Area Network (WAN)
When an organisation spans multiple buildings or cities, individual LANs are connected together to form a WAN. The links between LANs are usually owned by a third-party ISP such as BT or Virgin. Your school’s broadband connection to the internet is a WAN link.
- Connect sites across cities or countries
- Access shared resources from anywhere
- Single internet connection shared by all
- ISP subscription — ongoing cost
- ISP manages the link, not the organisation
- Slower than LAN — longer distances
- More complex to secure
The Internet — World’s Largest WAN
The Internet is a global WAN built from millions of interconnected LANs. Data travels as packets routed by routers. DNS (Domain Name Servers) translate human-readable web addresses into numerical IP addresses that routers use to direct traffic.
- Connects billions of devices worldwide
- Access any website, service, or resource
- Foundation of cloud computing
- Multiple routes — very resilient
- Public — major security risks
- Requires strong encryption (HTTPS)
- Speed depends on ISP bandwidth
- No single owner — difficult to regulate
Packet Switching
Files are too large to send in one go. Instead, data is broken into small packets. Each packet carries a header (source IP, destination IP, packet number, total count) and a payload (chunk of actual data). Packets travel independently and may take different routes — they are then reassembled in order at the destination.
- Network stays efficient — no line monopolised
- Packets reroute around failures automatically
- Multiple users share the same links
- Lost packet re-requested, not whole file
- Packets may arrive out of order
- Reassembly adds latency
- Congestion causes packet loss
- Header data adds overhead to each packet
Interactive: How packets travel
Network Protocols
A protocol is a set of agreed rules that govern how data is transmitted between devices on a network. Without protocols, devices made by different manufacturers could not communicate — like two people speaking different languages.
Protocols define: the format of data, the speed of transmission, error detection and correction, how connections are established and terminated, and how data is addressed and routed.
Key Protocols You Need to Know
HyperText Transfer Protocol — governs how web pages are requested and delivered between browser and web server.
HTTPS = HTTP + encryption (TLS/SSL). All data is encrypted — essential for login pages, banking, shopping.
Host: www.hautevallee.sch.je
File Transfer Protocol — used to upload and download files between computers across a network.
Web developers use FTP to upload website files to a server. SFTP (Secure FTP) adds encryption for safety.
SMTP (Simple Mail Transfer Protocol) — sends email from client to server and between servers.
IMAP — retrieves email, leaving it on the server (syncs across all devices).
POP3 — downloads email to one device and typically deletes it from server.
Transmission Control Protocol — establishes a connection, breaks data into packets, ensures they all arrive and are reassembled in the correct order.
Uses a three-way handshake (SYN → SYN-ACK → ACK) to establish a reliable connection before data is sent.
Internet Protocol — assigns IP addresses to every device and handles the routing of packets across networks. Routers use IP to decide where to forward each packet.
IPv6: 2001:0db8:85a3::8a2e:0370:7334
Domain Name System — translates human-readable domain names into numerical IP addresses. Like a phone book for the internet.
→ DNS lookup
151.101.0.81
The TCP/IP 4-Layer Model
Protocols are organised into layers. The TCP/IP model groups all network protocols into four layers, each responsible for a different aspect of communication. Data passes down through the layers when sending and up through the layers when receiving.
Each layer only communicates with the layer directly above or below it. This separation of concerns means each layer can be updated independently — a change to how WiFi works (layer 1) doesn’t require rewriting HTTP (layer 4).
Receiving reverses this: each layer strips its header and passes data up.
Click a Layer to Explore
FTP · SMTP
DNS · IMAP
MAC addresses
TCP vs UDP — Two Transport Protocols
TCP — Transmission Control Protocol
Establishes a connection first. Guarantees all packets arrive and are in order. Slower but reliable.
- Three-way handshake before data
- Packets acknowledged and re-sent if lost
- Data arrives in correct order
- Used by: HTTP, HTTPS, FTP, email
UDP — User Datagram Protocol
No connection established. Packets sent without checking arrival. Faster but unreliable.
- No handshake — data sent immediately
- Lost packets are not re-sent
- Lower latency — good for real-time data
- Used by: video streaming, VoIP, gaming
The Full Journey
Every time you load a web page, your computer breaks the request into packets, sends them through a LAN (using wired or wireless connections) to a router, which forwards them across the internet (a global WAN) via the fastest available route — governed at every step by agreed protocols organised into the TCP/IP four-layer model.
Key exam topics covered: Standalone vs networked computers, LAN vs WAN, star/bus/ring/mesh topologies, client-server vs peer-to-peer, wired vs wireless, NIC, WAP, packet switching, protocols (HTTP, HTTPS, FTP, SMTP, IMAP, POP3, TCP, UDP, IP, DNS), and the TCP/IP 4-layer model with encapsulation.