Principles of Internet Operation Revision
This revision lesson covers network fundamentals — LAN vs WAN, network topologies, hardware, and core Internet services like URL, DNS, and the client-server model.
Learning Objectives
- 11.6.1.1 Compare features of LAN and WAN
- 11.6.1.2 Describe advantages and disadvantages of network topologies
- 11.6.1.3 Explain the purpose of network equipment
- 11.6.2.1 Describe the role of URL
- 11.6.2.2 Describe the purpose of DNS
- 11.6.2.3 Know the features of the client-server model
Key Concepts Review
LAN vs WAN
| Feature | LAN | WAN |
|---|---|---|
| Coverage | Small area (room, building, campus) | Large area (city, country, worldwide) |
| Speed | High (100 Mbps – 10 Gbps) | Lower (depends on connection type) |
| Ownership | Private (owned by organization) | Public or leased (ISPs, telecom) |
| Cost | Lower setup and maintenance | Higher (infrastructure, leased lines) |
| Example | School network, office Wi-Fi | The Internet |
Network Topologies
| Topology | Advantages | Disadvantages |
|---|---|---|
| Star | Easy to add devices; one failure doesn't affect others | Central hub/switch is a single point of failure |
| Bus | Simple; cheap cabling | One cable break stops entire network; collisions |
| Ring | No collisions; orderly data flow | One device failure breaks the ring |
| Mesh | Highly reliable; multiple paths for data | Expensive; complex wiring |
Network Hardware
| Device | Purpose |
|---|---|
| Hub | Broadcasts data to all connected devices (no intelligence) |
| Switch | Sends data only to the intended device using MAC addresses |
| Router | Routes data between different networks using IP addresses |
| NIC | Network Interface Card — connects a device to the network |
| WAP | Wireless Access Point — allows wireless connections to LAN |
URL, DNS & Client-Server
1 URL Structure
https://www.example.com:443/page/index.html?id=1#section
│ │ │ │ │ │ │
protocol subdomain domain port path query fragmentDNS (Domain Name System)
DNS translates domain names (www.google.com) into IP addresses (142.250.74.46). Without DNS, you would need to memorize IP addresses to visit websites. DNS servers form a hierarchy: browser cache → local DNS → root → TLD → authoritative.
Client-Server Model
A client sends requests (e.g., your browser). A server processes requests and sends responses (e.g., web server). The server is always running, waiting for connections. Multiple clients can connect to one server simultaneously.
Revision Tasks
State 3 differences between LAN and WAN.
Explain how DNS resolves a domain name to an IP address.
Draw a star topology with 5 devices and a central switch. Label each component.
Compare star and mesh topologies. Which is more suitable for a hospital network and why?
Self-Check Quiz
Q1: What does DNS stand for and what does it do?
Q2: What is the difference between a hub and a switch?
Q3: In the client-server model, which sends the request?