LAN and WAN

Have you ever sent a document from your phone in the bedroom to a wireless printer in the living room? A network where devices are linked together inside a small, limited physical space like a home, an office, or a school is called a LAN (Local Area Network).

Inside a LAN, radio waves and cables only have to travel a very short distance. Signals don't need to go far, so data moves very fast and rarely drops out along the way. A device like a wireless router or a switch sits at the center and holds the nearby computers, phones, and TVs together as one group.

Inside these walls, your devices can swap high-resolution photos and big video files in an instant, without paying your carrier for expensive data. It's like building a fast private network that only your family or coworkers can join. But some LANs, like a coffee shop's Wi-Fi, are shared with strangers. A LAN isn't automatically safe just because it's a LAN.

Sending files between your laptop and phone on the same coffee shop Wi-Fi, or switching your smart lights on and off from your phone at home, are everyday scenes that LANs make possible.

But a LAN at home can't show you a video stored on a server across the ocean in the United States. A LAN only works inside its own walls, and it isn't directly connected to the world outside.

A huge network that ties together LANs in cities, countries, and continents far from each other is called a WAN (Wide Area Network). It connects a head office in Seoul to a branch in Busan, or links users all over the world.

A WAN has to cover distances from tens of kilometers between cities to more than 10,000 kilometers between continents. No individual can lay that much wire or cable. So data travels over big fiber-optic cable networks that telecom companies have buried deep underground and laid on the ocean floor, and you borrow that capacity.

When we talk about web surfing, online games, or global streaming services, they all run over the biggest WAN on Earth: the internet.

So how can your home LAN, a narrow alley, freely trade data with a WAN, a wide highway? The secret is a piece of network equipment inside your Wi-Fi box called a router.

The router hands out internal addresses to the many devices in your home. It also acts like a traffic cop, finding the fastest route for data heading outside. When your phone asks to open a website, the router swings open the gate of the LAN and sends the signal out onto the WAN's wide road.

These two networks, divided by distance, work together. The devices in a home or company form a small circle called a LAN, and through the router they step out into a huge worldwide square called a WAN.

In the end, when you use the internet, your data leaves the LAN where it started, travels back and forth along the global highway of the WAN, and brings the information from its destination safely back to you.