The problem networks solve
Asha works in a small office. She needs to print a report, open a file a colleague saved, and look something up on a website. Without a network, she would copy the report to a USB stick, walk it to the printer's computer, and have no internet at all.
A network fixes this by connecting the devices, so they can send data to each other directly. Every office, home and data centre uses one for the same reasons: to share things (files, printers, an internet connection) and to communicate (email, chat, video calls).
What a network is
A network can be very small: two laptops joined by one cable are a network. Your home Wi-Fi is a network. The internet is the largest one, made by connecting millions of smaller networks together.
Whatever the size, every network is built from the same four parts:
| Part | What it does | In Asha's office |
|---|---|---|
| End devices | Create and use the data | Laptop, printer, web server |
| Network devices | Move data between end devices | Switch, router |
| Media | Carry the signal | Copper cables (Ethernet) |
| Protocols | Shared rules for talking | Ethernet, IP, HTTPS |
A switch connects devices inside one network. A router connects one network to another, for example the office to the internet.
How it works: Asha prints and opens a website
Data travels in small pieces called packets. Each packet carries the IP address of where it is going, like the address on an envelope. Watch two packets: one to the printer and one to a website.
Tip: click or tap a device or the moving packet to see its details.
- 1. Print: the printer is in the same network, so the switch delivers the packet directly. The router is not involved.
- 2. Website: example.com is on another network, so the packet goes to the router, which sends it out to the internet.
- 3. Reply: the web server answers, and the router passes the reply back to Asha's laptop.
What to notice:
- The print job never reaches the router. Traffic inside one network only needs the switch.
- Anything going outside the office passes through the router. It is the network's way out.
- Each device has its own address, so every packet knows where to go.
💡 In simple terms: the switch is like the post room inside one building; the router is the door to the outside world.
Learn more: SwitchesRoutersWhat Is an IP Address?
Client-server and peer-to-peer
There are two ways for devices to share. In client-server, a server provides a service and clients ask for it. Asha's browser is a client; example.com is a server.
Tip: click or tap a device to see its details.
- 1. Request: a client asks the server for a file.
- 2. Response: the server sends it back.
- 3. Many clients: one server answers them all.
In peer-to-peer (P2P) there is no server: each device shares directly with the others, as when you AirDrop a photo.
| Client-server | Peer-to-peer | |
|---|---|---|
| Who provides it? | A server | Every device |
| Best for | Many users, shared data | A few devices |
| Examples | Websites, email, file servers | AirDrop, home folder sharing |
A server is a role, not a special computer: any device that provides a service is acting as a server.
Home, office and enterprise networks
The ideas are the same at every size. What changes is how many devices there are and how many separate boxes share the work. At home, one box does almost everything:
Tip: click or tap a device to see its details.
- 1. Join: devices connect to the home router over Wi-Fi.
- 2. Out: the router sends their traffic to the internet.
| Home | Small office | Enterprise | |
|---|---|---|---|
| Devices | 5 to 50 | 10 to 200 | Thousands |
| Network devices | One home router | A router or firewall, switches, access points | Many of each, in layers, with spare paths |
| Run by | The household | One IT person | A network team |
Learn more: Types of Networks
Check your own network
On Windows, open Command Prompt and run ipconfig. It shows your device's address and its router:
C:\>ipconfig Wireless LAN adapter Wi-Fi: IPv4 Address. . . . . . . . . . . : 192.168.1.20 Subnet Mask . . . . . . . . . . . : 255.255.255.0 Default Gateway . . . . . . . . . : 192.168.1.1
ifconfig or ip addr.Then run ping 192.168.1.1 (use your own gateway address). Replies mean your device can reach the router, so your local network works.
Advanced: two kinds of address
Every device on an Ethernet or Wi-Fi network has two addresses. The MAC address (for example 02:00:00:00:00:20) is used by switches to deliver data within one network. The IP address (for example 192.168.1.20) is used by routers to deliver data between networks.
When a packet crosses a router, the router puts it in a new frame with new MAC addresses. The IP addresses inside normally stay the same from end to end; the exception is NAT, which you saw when the router changed Asha's source address to 203.0.113.2.
Learn more: MAC AddressesHow NAT and PAT Work
Common mistakes
- Thinking Wi-Fi is the internet. Full Wi-Fi bars only mean you reach the local network.
- Confusing a switch with a router. A switch connects devices in one network; a router connects networks.
- Thinking a server is a special computer. Any device that provides a service is a server.
Practice
Exercise: sketch your own home network on paper. Mark the end devices, the network device(s), the media (cable or Wi-Fi) and one protocol you use every day. Then run ipconfig and write your IP address and default gateway next to your device.
Asha can print, but no websites load. Which device should she suspect first?
Your browser loads a page from example.com. Which roles are they playing?
Two laptops are joined by one cable and can share files. Is this a network?