How does the internet work?
The short answer
The internet moves data in packets. A page is cut into numbered packets, each addressed to your device. Routers forward every packet one hop closer and send it around a broken link, so packets can take different routes and arrive out of order. Your device sorts them by number and asks again for any that were lost.
Chapters and transcript
- 0:00
Your page does not travel as one piece.
When you open a page, it does not cross the internet in one piece.
- 0:10
It is cut into numbered packets.
The server cuts it into small packets and numbers each one, so the page can be put back together.
- 0:16
Each packet carries an address.
Every packet carries the address it is going to, so each one can travel on its own.
- 0:21
Each router passes it one hop closer.
Each router reads the address and sends the packet one link closer. No router knows the whole way.
- 0:26
A broken link? They go around it.
When a link breaks, routers send the packets that have not crossed it yet along another working path.
- 0:31
They arrive out of order.
Packets that took different routes arrive in a different order from the one they were sent in.
- 0:37
A missing one is asked for again.
One packet was lost on the way. Your device sees the gap in the numbers and asks for it again.
- 0:48
The server sends it again.
The server sends that packet again, and it finds its own route.
- 1:01
The page is rebuilt, in order.
Your device sorts the packets by number and rebuilds the page.
- 1:14
Every page is many packets, each with its own route.
Everything on the internet moves this way: many small packets, each finding its own route.
- 1:25
No one planned the whole route.
No single machine planned the path. Each router only chose the next hop.
Sources
Every figure in the film comes from these. The animation is illustrative.