Computer Science Principles The Internet - 03 Addressing and Routing Information - 01 Sending and receiving information

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Everything that we create on a computer is translated into digital information using bits.

This could mean a collection of thousands, millions, or billions of bits, or more, need to have a way to be transmitted over the internet.

But, in order to do that, there needs to be a way to take the information and break it down, so we have a reliable way to send it over the network.

Every message, file, or stream of information is broken down into small chunks, called packets.

When packets are sent on the internet, they usually will travel the network together.

But, take a situation like a road trip.

If you and your friends are in four separate cars, and you're going down the highway, at a certain point there might be an accident cutting off the route of two people.

They might have to take a different route to get to the destination.

To help with this, each packet contains some important information inside of it called the header.

First, the packet says where it came from.

This is like the return address on an envelope.

If the place it is trying to go to doesn't exist, or there's a problem, there's a way for the network to send a message back to the sender to let them know that the message didn't go through.

It also is helpful to know that if a message was successfully sent, that there is an acknowledgement of that sent back to the sender.

Next, the packet needs to know where it's going to.

This is the address you have on an envelope.

This way, if a packet gets lost or has to go in a different way, the network can point it in the right direction for it to get to the right destination.

The packet also needs to say how long it is.

It stores that by defining the number of bytes that are in the packet.

This way, we know the packet is complete.

All the packets in the message are the same size, so if one isn't the same size as the others, we know we have lost some data, and we can find a way to get it back.

Finally, we need to know how many packets there are in the overall message, and in which place each individual packet lives within the set.

Using packets, and the header information inside of them, we can take a message of any size and break it down into chunks that can be transmitted over the internet.