Computer Science Principles The Internet - 03 Addressing and Routing Information - 02 The Internet Protocol and IP address

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When you send a letter or package, you need to provide an address.

The address needs to be understood by everyone that comes into contact with it, to make sure that it's going to the right place, and that it's being delivered to the right person.

When we address a letter, we use a country, state, city, street, and house number.

With these, we are able to get the letter closer and closer, to the right person among millions of people.

Everyone has a unique name and address.

Well, unless you live with an identical twin with the same name.

The same exists with addresses on the Internet.

Instead of a street address, addresses on the Internet use numbers.

The use of numbers as addresses is one of the core concepts of the Internet, and it is called the Internet Protocol, or IP.

Each device on the Internet has an address called an IP address.

With IPv4, a current standard, this is a sequence of four, three-digit numbers separated by a period.

Each number can be a number from zero to 255, allowing for over four billion possible addresses on the Internet.

Using these numbers, networks, sub-networks, servers, and individual devices, can be reached from any other device on the network.

Each packet that is sent, has the sender and the receiver addresses in the header.

These are stored as IP addresses.

This way, the network has a way to see where it needs to send each packet, and if there's a problem, where to send the error, or the issue back to the sender.

With IP addresses, there are public addresses, and private ones.

There's an organization called the Internet Assigned Numbers Authority, or IANA, that determines what numbers and subsets are assigned to different groups.

Within these groups there is the public addresses your device has on the Internet, and a private one you have on your home network.

Here's an example.

I might have a tablet that is on my home network.

My router has a connection to my Internet provider, and I have a public address.

On my home network, my router gives each device, including my tablet, a private address.

So the job of the router, is to route, the packets from the public Internet, to my private device and vice versa.

Using the Internet Protocol and IP addresses, every device can connect to a network of millions of other devices, and packets of information can be sent to any of them.