Big data in small pieces: the packet

It can't go all at once

Here is one big piece of data.
A photo, a video, a big file.
We want to send it whole,
all at once.
But the road is narrow.
A big lump does not fit on the road.
So as one whole lump
it cannot even set off.
Let's see this for ourselves first.

Tap the big data lump to send it whole. The road is too narrow, so it can't go in one piece.

We tried to push it through whole
and it got stuck at the entrance.
The lump was too big
to fit the narrow road.
The real internet road is the same.
There is a fixed size
you can send at one time.
So there is only one way.
Cut it into small pieces.

Cut it into pieces

Let's cut the big lump.
We split one lump
into several small pieces.
Each piece is sized
to slip onto the narrow road.
This small piece is called a packet.
It is like taking a long letter
and splitting it across several envelopes.
Now the pieces can set off.

Tap the data lump to split it into small packets. Each tap divides off a piece.

The big lump
became several pieces.
Now each piece can go
onto the narrow road one by one.
But a problem appeared.
The pieces all look the same.
We can't tell which is which number,
or where each one should go.
So each piece needs a mark.

Attach a tag

We attach a tag to each piece.
The tag says two things.
One is the number.
It tells which piece this is in order.
The other is the address.
Where this piece needs to go.
With just a number and an address,
even if a piece loses its way
it can find its place.

Tap a packet to attach a number and destination address tag. Every piece gets a tag.

Now each piece
has a number and an address on it.
The pieces set off.
But they do not have to go
side by side on the same road.
If one road is blocked
a piece takes another road.
So the pieces can even arrive
in a jumbled order.

Reassemble on arrival

All the pieces have arrived.
But their order is mixed up.
Number 3 might come first
and number 1 come later.
No worries.
Each piece has its number on it.
Line them up in number order
and the scattered pieces
become the original data again.

Tap the scattered packets in number order (1, 2, 3, 4) to join them back into the original data.

Joined in number order,
the original data came back.
The split photo
became one picture again.
The receiver
never even notices
that the pieces came separately.
They just see the finished photo.
This is how packets work.

Let's wrap up

Gathered on one line, it's this.
Big data cannot be sent all at once.
So we cut it into small packets.
Each piece gets a number and address tag.
Pieces can travel separately,
so a blocked road can be gone around.
On arrival they join in number order.
Split, tag, and reassemble.
That is a packet.

Tap the key points in order to review. (split → tag (number + address) → send separately → join in number order)

Now you know what a packet is.
Even big data, cut into pieces,
can go far over a narrow road.
But the address a piece must reach,
what does it actually look like?
Among countless computers,
how do we find just one?
Next lesson, let's follow
the story of that address together.