Computer networks

What is computer networking?

Computer networking is the study of connecting devices together so they can share information — from two computers in the same room to the entire global internet connecting billions of devices.

Layers: why networking is split into separate jobs

Network communication is organized in layers, each handling one specific job, and each only needing to know how to talk to the layer directly above and below it — not every other layer at once. The physical layer handles actual electrical or radio signals; higher layers handle addressing, and then the actual data an application wants to send. This division matters concretely: a web browser's code doesn't need to know anything about how Wi-Fi radio signals work, and a Wi-Fi chip doesn't need to know anything about what a web page is — each layer's job stays independent and reusable, so improving or replacing one layer (switching from Wi-Fi to a wired cable, for instance) doesn't require rewriting anything in the layers above it.

IP addresses: an address for every device

An IP address identifies a specific device on a network, similar to how a postal address identifies a specific building — a device needs to know another device's IP address before it can send it any information, exactly the way a letter needs a destination address before it can be delivered.

Packets: why data gets broken into pieces

Rather than sending an entire file as one single, uninterrupted transmission, networks break data into smaller pieces called packets, each sent and routed somewhat independently. This has two concrete, direct benefits: if a single packet is lost or corrupted in transit, only that small piece needs to be resent, not the entire file; and breaking data into packets lets many different transmissions share the same network connection fairly, interleaved with each other, rather than one large transfer monopolizing the connection until it finishes entirely.

Why computer networking matters

Every online interaction — loading a web page, sending a message, making a video call — depends on this layered, packet-based system working correctly and efficiently, reliably moving data between devices that may be on opposite sides of the world, through many intermediate networks along the way.