How messages travel on the internet

Ages 9 to 12 Read alone or together · about 40 minutes

Read together

The internet is a network of networks. A message does not travel in one piece. It is broken into small parts called packets.

Each packet has an address and a number. Machines called routers send each packet along the best path they know. Packets may take different routes.

At the end, the packets are put back in order so you can read the message. Early versions of this idea were described in the 1970s.

Do it

1. Write a short message of twelve words on a strip of paper. Cut it into six pieces of two words and number them.
2. Each piece goes in a separate envelope with an address. Give the envelopes to different friends to “route” by hand across the room.
3. Mix them up at the receiving end. Put the pieces back in order using the numbers. Did the message arrive?
4. Remove one envelope. How could the receiver know a packet is missing?

Talk about it

• Why break a message into packets?
• What if a router fails?

For the grown-up

Packet switching makes the internet flexible, because if one path fails, packets can use another. The 1974 paper by Vint Cerf and Bob Kahn described the protocol design that became the internet's foundation. Messages on the internet can be read by others unless they are encrypted, so keep private matters safe.

Mark as done

← Previous lesson Next lesson →

Where this comes from

• Vinton G. Cerf and Robert E. Kahn, “A Protocol for Packet Network Intercommunication”, IEEE Transactions on Communications 22 (1974): 637 to 648
• Internet Society, “Brief History of the Internet”

Written with AI assistance and checked against the sources listed. Please read it before sharing it with a child.