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Hi! My name is Paola,and I am a software engineer at Microsoft.

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Let's talk about how the internet works. My job relies on networks being able

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to talk with one another, but back in the 1970s there was no standard method for this.

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It took the work of Vint Cerf and Bob Kahn to invent the internetworking protocol, to make communication possible.

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This invention laid the groundwork for what we now call the internet.

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The internet is a network of networks. It links billions of devices together all

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around the globe. So maybe you're connected with a laptop or a phone through wifi, then

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that wifi connection connects to an internet service provider (or ISP), and that ISP connects

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you to billions and billions of devices around the world through hundreds of thousands of

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networks that are all interconnected.

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One thing that most people do not appreciate is that the internet is really
a design philosophy and an architecture expressed in a set of protocols.

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A protocol is a well known set of rules and standards, that if all parties

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agree to use it will allow them to communicate without trouble.

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How the internet actually physically works is less important than the fact that this design philosophy

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has allowed the internet to adapt and absorb new communication technologies.

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This is because in order for a new technology to use the internet in some fashion, it just needs to know which protocols to work with.

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All the different devices on the internet have unique addresses.

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An address on the internet is just a number, similar to a phone number or a sort of street address,

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that's unique to each computer or device at the edge of the network.

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This is similar to how most homes and businesses have a mailing address. You don't need to know a person to

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send them a letter in the mail, but you do need to know their address and how to write

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the address properly so the letter can be carried by a mail system to its destination.

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The addressing system for computers on the internet is similar and it forms part of one

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of the most important protocols used in internet communication simply called the internet protocol or IP.

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A computer's address then is called its IP address. Visiting a website is really

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just your computer asking another computer for information. Your computer sends a message

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to the other computer's IP address and it also sends along its origin address, so the

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other computer knows where to send its response.

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You may have seen an IP address.It's just a bunch of numbers!

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These numbers are organized in a hierarchy.

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Just like a home address has a country, a city, a street, and a house number,

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an IP address has many parts. Just like all digital data, each of these numbers is represented in bits.

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Traditional IP addresses are 32 bits long, with 8 bits for each part of the address.

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The earlier numbers usually identify the country and regional network of the device.

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Then come the subnetworks, and then finally the address of the specific device.

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This version of IP addressing is called IPv4.

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It was designed in 1973 and was widely adopted in the early 80s,

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and provides for more than 4 billion unique addresses for devices connecting to the internet.

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But the internet has turned out to be much more popular than even Vint
Cerf imagined and 4 billion unique addresses won't be enough.

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We're now in the middle of a multi-year transition to a longer IP address format

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called IPv6, which uses 128 bits per address and provides over 340 undecillion unique addresses.

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That's more than enough for every grain of sand on Earth to have its own IP address.

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Most users never see or care about internet addresses.

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A system called the domain name system or DNS associates names like www.example.com with the corresponding addresses.

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Your computer uses the DNS to look up domain names and get the associated IP

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address which is used to connect your computer to the destination on the internet.

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And it goes a little something like this: (voice1) "Hey, hi there, I want to go to www.code.org."

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(voice 2) "Mm.. yeah I don't know the IP address for that domain let me ask around.
Hey, do you know how to get to code.org?"

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(voice 3) "Yeah, I got it right here it's 174.129.14.120."

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(voice 2) "Oh okay, great, thanks. I'm gonna write that down and save it for later in case I need it again.

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Hey here's that address you wanted." (voice 1) "Awesome! Thank you."

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So how do we design a system for billions of devices to find any one of billions of different websites?

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There is no way one DNS server can handle all the requests from all devices.

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The answer is that DNS servers are connected in a distributed hierarchy, and are divided into zones,

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splitting up responsibility for the major domains such as .org, .com, .net, etc.

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DNS was originally created to be an open and public communication protocol for government

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and educational institutions. Because of its openness, DNS is susceptible to cyber attacks.

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An example attack is DNS spoofing. That's when a hacker taps into a DNS server and changes

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it to match a domain name with the wrong IP address. This lets the attacker send people to an imposter website.

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If this happens to you, you are vulnerable for more problems

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because you are using that fake website as if it's real. The internet is huge and getting bigger everyday.

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But the domain name system and internet protocol are designed to scale,

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no matter how much the internet grows.