1. The Basics: What is a Network?
A network is just two or more computers connected so they can "talk" to each other. They do this to share files or equipment like printers.
LAN vs WAN
- LAN (Local Area Network): Small scale. Think of your house or school. You own the cables and routers.
- WAN (Wide Area Network): Large scale. Think of a city or the whole world. You have to "rent" the lines from big companies like BT or Virgin.
Performance Factors
Factors Affecting Speed:
- Bandwidth: The maximum data rate (bits per second).
- Number of Users: High traffic causes data collisions.
- Latency: The time delay between sending and receiving.
Wired vs Wireless:
- Ethernet: Fast, stable, and secure.
- Wi-Fi: Portable but interference from walls/signals.
- Bluetooth: Very short range (10m) for peripherals.
2. Network Hardware (The "Stuff" You Need)
NIC (Network Interface Controller): The internal hardware that lets a device connect to a network.
Switch: Connects devices on a LAN. It "learns" MAC addresses to send data only to the intended recipient.
Router: The "bridge" that connects different networks (e.g., your home LAN to the Internet WAN).
WAP (Wireless Access Point): Creates the Wi-Fi signal.
3. Topologies (The Layout)
Star Topology
Everything plugs into one central switch.
[Image of a star network topology diagram]
The Good: If one computer's cable breaks, others are fine. Easy to add new devices.
The Bad: If the central switch breaks, the whole network fails.
Mesh Topology
Every computer connects to every other computer.
[Image of a mesh network topology diagram]
The Good: Highly reliable. If one path fails, data takes another (Self-healing).
The Bad: Very expensive and complex due to the amount of cabling needed.
4. The Cloud & DNS
The Cloud: Storing files and running applications on remote servers over the internet instead of your local hard drive.
Pros: Access from any device, easy collaboration, automatic backups.
Cons: Requires internet, subscription costs, reliance on provider security.
DNS (Domain Name System): Turns human-readable URLs (queryed.com) into numeric IP addresses (192.168.1.1) so routers know where to send your request.
5. Protocols & The 4-Layer Model
A Protocol is a set of rules for communication. We use Layers so that changing one part of the network (like upgrading a browser) doesn't break the hardware.
1. Application: HTTP, HTTPS, SMTP, IMAP, FTP.
2. Transport: TCP (splits data into packets).
3. Internet: IP (addresses and routes packets).
4. Link: Ethernet, Wi-Fi (physical hardware).
Practice Quiz (20 Questions)
Exam-Style Practice (Longer Answers)
Try to answer these in 2-3 sentences:
- Question: Explain one advantage of using a Star topology over a Mesh topology.
- Question: Why does a network's performance slow down when 30 people try to watch YouTube at the same time?
- Question: Describe how the DNS helps a user visit a website.