What a network connects

Why this matters

A network lets devices exchange data across links. “The internet” is not one invisible object: your device first uses a local interface and local network, then other devices can forward data toward another network.

The first vocabulary

• A device is a computer, phone, printer, router or other system participating in the network.
• A network interface is the point through which a device connects, such as Ethernet or Wi-Fi.
• A link carries data between connected interfaces.
• A packet is a unit of data with control information and a payload.
• A client requests a service; a server provides one. These are roles in an interaction, not fixed sizes of computer.

Local is not global

Devices connected to the same local network can often exchange data directly. Reaching a different network normally requires a router. Before the computer can make that decision, it needs an address and information about which destinations count as local.

Common mistakes

• Wi-Fi is one way to connect to a network; it is not a synonym for the internet.
• A client and server are roles. One system can act as both in different exchanges.
• A packet is not the complete conversation; it is one unit inside an exchange.

Mini challenge

Draw your current path as roles only: device → interface → local connection → network device. Do not guess product models or public addresses.

Next stepIP addresses and local networks

Give interfaces logical addresses and decide which destinations are local.