The telecom building

Reading the address, choosing the road

Below the tower, the request enters a cable under the ground and arrives at a telecom building. Inside are rows of route-finding machines. Each one reads the address on the request and chooses the next path, like "for the US, take this cable." The request passes through several of these machines and heads for the Busan coast.

Why?It works like a parcel sorting center, which reads each address and loads the parcel onto the right truck. No single place needs to know the whole route. Each one only needs to know where to send it next.

Learn moreThese machines are called "routers," and the building is called a "central office." Routers keep telling each other how far they can reach. So if one path breaks, they find another way around.

Time

4 ms → 6 ms

Simplified route · light in glass at about 200,000 km per second