The address book
A name is looked up and turned into a number. That lookup is a question, not a building the request walks through.
One more sentence, for a grown-up
People type names. Computers use numbers. The lookup often starts at the device or the router, and the answer can be remembered for a while. Roughly, as of 2026, that number is still how machines find each other.
This picture is an idea, not a thing with a size.
Real: What it looks like.
- Packets
- The reply
Keys: arrows rotate · + / − zoom · 0 reset · 1–4 views · S signal · T tour · L labels · Space spin. The model is stylised. The network on this page is made up.
Every labeled part
- 1
The name
A person-readable name, like the words in a link.
- 2
The book
Something answers: this name currently means this number.
- 3
The number
Other computers use the number, not the name.
- 4
A missing name
If the name is not in the book, there is no number to send the request to.
- Packets
- The reply
Try it