A neighbor typed the name of a story site into his web browser. "How did my tablet know where that site lives?" he asks. "Names are just words!"
Rocket shrugs. Raven looks at the envelope on the desk. "What do you notice about how a letter finds a house?"
Nova glows. "Would you like a hint? Every device on a network has a number address. A name has to be turned into a number first."
A letter needs a house address. A packet needs a device address.
Every device on a network gets a number address. The router gives your tablet one when it joins the home network.
A packet carries two addresses: where it came from and where it is going. Routers read the going-to address and pass the packet along.
People do not like remembering long numbers, so sites have names. When you type a name, your device asks a lookup service for the number.
The lookup service is like a phone book. Name in, number out. Then the packets can be sent.
| What you use | What the network uses | Like |
|---|---|---|
| A site name | A number address | A friend's name and their house address |
| Typing a name | Looking up the number | Finding a name in a phone book |
A packet does not jump straight to its destination. It hops from router to router.
Each router reads the going-to address and passes the packet one hop closer. Like a relay race, each runner hands it on.
A packet might make ten or twenty hops to cross the world. It all happens in less than a second.
| Statement | True or false? |
|---|---|
| Networks send packets to names, not numbers. | ? |
| Each router reads the address and passes the packet along. | ? |
| A packet usually hops through several routers. | ? |
| The journey across the world takes many minutes. | ? |
You followed a packet across the world! Tomorrow the crew puts the whole journey together for a video call.