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The Internet: IP Addresses and DNS

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Hi! My name is Paola,[br]and I am a software engineer

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at Microsoft. Let's talk about how the internet[br]works. My job relies on networks being able

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

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It took the work of Vint Cerf and Bob Kahn[br]to invent the internetworking protocol, to

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make communication possible. This invention[br]laid the groundwork for what we now call the

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

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

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

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

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networks that are all interconnected. One[br]thing that most people do not appreciate is

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that the internet is really a design philosophy[br]and an architecture expressed in a set of

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protocols. A protocol is a well known set[br]of rules and standards, that if all parties

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agree to use it will allow them to communicate[br]without trouble. How the internet actually

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physically works is less important than the[br]fact that this design philosophy has allowed

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the internet to adapt and absorb new communication[br]technologies. This is because in order for

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a new technology to use the internet in some[br]fashion, it just needs to know which protocols

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to work with. All the different devices on[br]the internet have unique addresses. An address

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

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that's unique to each computer or device at[br]the edge of the network. This is similar to

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how most homes and businesses have a mailing[br]address. You don't need to know a person to

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

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

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

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of the most important protocols used in internet[br]communication simply called the internet protocol

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or IP. A computer's address then is called[br]its IP address. Visiting a website is really

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

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

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other computer knows where to send its response.[br]You may have seen an IP address. It's just

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a bunch of numbers! These numbers are organized[br]in a hierarchy. Just like a home address has

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a country, a city, a street, and a house number,[br]an IP address has many parts. Just like all

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digital data, each of these numbers is represented[br]in bits. Traditional IP addresses are 32 bits

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long, with 8 bits for each part of the address.[br]The earlier numbers usually identify the country

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and regional network of the device. Then come[br]the subnetworks, and then finally the address

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of the specific device. This version of IP[br]addressing is called IPv4. It was designed

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in 1973 and was widely adopted in the early[br]80s, and provides for more than 4 billion

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unique addresses for devices connecting to[br]the internet. But the internet has turned

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out to be much more popular than even Vint[br]Cerf imagined and 4 billion unique addresses

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won't be enough. We're now in the middle of[br]a multi-year transition to a longer IP address

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format called IPv6, which uses 128 bits per[br]address and provides over 340 undecillion

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unique addresses. That's more than enough[br]for every grain of sand on Earth to have its

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own IP address. Most users never see or care[br]about internet addresses. A system called

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the domain name system or DNS associates names[br]like www.example.com with the corresponding

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addresses. Your computer uses the DNS to look[br]up domain names and get the associated IP

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address which is used to connect your computer[br]to the destination on the internet. And it

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goes a little something like this: (voice[br]1) "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[br]for that domain let me ask around. Hey, do

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you know how to get to code.org?" (voice 3)[br]"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[br]write that down and save it for later in case

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I need it again. Hey here's that address you[br]wanted." (voice 1) "Awesome! Thank you." So

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how do we design a system for billions of[br]devices to find any one of billions of different

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websites? There is no way one DNS server can[br]handle all the requests from all devices.

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The answer is that DNS servers are connected[br]in a distributed hierarchy, and are divided

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into zones, splitting up responsibility for[br]the major domains such as .org, .com, .net,

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etc. DNS was originally created to be an open[br]and public communication protocol for government

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

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

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it to match a domain name with the wrong IP[br]address. This lets the attacker send people

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to an imposter website. If this happens to[br]you, you are vulnerable for more problems

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

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bigger everyday. But the domain name system[br]and internet protocol are designed to scale,

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no matter how much the internet grows.