The big ideaA message is cut into packets that travel by different roads, then put back together.
How it works
A message, like a picture, is cut into small pieces called packets. Each packet gets a label with a number and the place it is going.
The internet is a huge network of computers joined together. Helper computers called routers send each packet on its way.
Packets do not all take one road. If a road is busy, a router sends packets another way.
Packets can arrive in any order. The other computer uses the numbers to put them back in order, and then shows the whole message.
Arriving in any order, then in order.
Example 1: Cutting it up
Mina's dragon picture is cut into packets.
Each packet is labeled with its number and the place it is going.
There is packet one, packet two, packet three, and more.
Example 2: A busy road
One road is busy and slow.
A router sends packets another way.
That is how the internet keeps going, even when one road is busy.
Example 3: Out of order
At Sam's house number four comes first, and number two comes last.
Sam's computer does not mind and keeps catching the packets.
It uses the numbers to put them in order: 1, 2, 3, 4, 5, 6.
Example 4: Which are missing
The dragon is cut into six packets, and packets 4, 1, 6 and 3 have arrived.
The packets are 1, 2, 3, 4, 5 and 6, so the ones not here are 2 and 5.
Packets 2 and 5 are still on their way.
Words to know
packet
A small piece of a message.
router
A helper computer that sends each packet onward.
internet
A huge network of computers joined together.
network
Computers joined together so they can share messages.
Watch out
A message is not one big lump. It travels as small packets.
Packets can take different roads, so they can arrive out of order.
The number on a packet is what puts the message back together.
A router sends a packet onward. It does not keep the message.
Try it
What is a packet?
What does a router do?
Why does each packet have a number?
True or false: all packets must take the same road.
The packets arrive as 3, 1, 2. What order does the other computer put them in?
Answers: 1. A small piece of a message · 2. Sends each packet onward · 3. So the packets can be put back in order · 4. False · 5. 1, 2, 3
Try at homeWith a grown-up, write a short message in four pieces on four cards. Number each card on the back. Shuffle the cards, then ask your grown-up to put them back in order using only the numbers. That is how a computer puts packets back together.
For grown-upsDo the Mission: write a short message in four pieces on four cards, number each card on the back, shuffle them, and ask your child to put them back in order using only the numbers. That is how a computer puts packets back together.
Open these notes on screenScan the code, or go to tutorpip.com.