The Internet: IP addresses and DNS

(upbeat piano and drum music)

- Hi. My name is Paola,

and I am a software engineer at Microsoft.

Let's talk about how the internet works.

My job relies on networks being able

to talk with one another.

But back in the 1970s, there was no

standard method for this.

It took the work of Vint Cerf and Bob Kahn

to invent the Internetworking Protocol

to make communication possible.

This invention laid the groundwork

for what we now call the internet.

- The internet is a network of networks.

It links billions of devices
together all around the globe.

Maybe you're connected with a laptop

or a phone through wifi.

But then that wifi connection

connects to an Internet
Service Provider, or ISP.

And that ISP connects you
to billions and billions

of devices around the world

through hundreds of thousands of networks

that are all interconnected.

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.

A protocol is a well-known set
of rules and standards that,

if all parties agree to use it,

will allow them to
communicate without trouble.

How the internet actually
physically works is less important

than the fact that this
design philosophy has allowed

the internet to adapt and absorb

new communication technologies.

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.

All the different devices on the internet

have unique addresses.

An address on the
internet is just a number,

similar to a phone number,
or a sort of street address

that's unique to each computer or device

at the edge of the network.

This is similar to how most
homes and businesses have

a mailing address.

You don't need to know a person

to send them a letter in the mail,

but you do need to know their address,

and how to write the address properly,

so the letter can be
carried by the mail system

to its destination.

The addressing system for computers

on the internet is similar,

and it forms part of one
of the most important

protocols used in internet communication,

simply called the
Internet Protocol, or IP.

A computer's address, then,
is called its IP address.

Visiting a website is really
just your computer asking

another computer for information.

Your computer sends a message
to the other computer's

IP address, and it also sends
along its origin address

so the other computer knows
where to send its response.

- You may have seen an IP address.

It's just a bunch of numbers.

These numbers are
organized in a hierarchy.

Just like a home address has a country,

a city, a street, and a house number,

an IP address has many parts.

Just like all digital data,

each of these numbers
is represented in bits.

Traditional IP addresses are 32 bits long,

with eight bits for each
part of the address.

The earlier numbers usually identify

the country and regional
network of the device.

Then come the subnetworks.

And then, finally, the address
of the specific device.

This version of IP
addressing is called IPv4.

It was designed in 1973,

and widely adopted in the early '80s,

and provides for more than
4 billion unique addresses

for devices connecting to the internet.

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.

We're now in the middle
of a multi-year transition

to a longer IP address format called IPv6,

which uses 128 bits per address,

and provides over 340
undecillion unique addresses.

That's more than enough for
every grain of sand on Earth

to have its own IP address.

- Most users never see or
care about internet addresses.

A system called the Domain
Name System, or DNS,

associates names, like www.example.com,

with the corresponding addresses.

Your computer uses the DNS
to look up domain names

and get the associated
IP address, which is used

to connect your computer to the
destination on the internet.

- [Voiceover] And it goes a
little something like this.

- Hey, hi there.

I want to go to www.code.org

- Yeah, well I don't know the
IP address for that domain.

Let me ask around.

Hey, anyone know how to get to a...

code.org?

- Yeah, I got it right here.

It's 174 dot 129

dot 14 dot 120.

- Oh, okay, great. Thanks.

Yeah, I'm gonna write that
down and save it for later

in case I need it.

Hey, here's that address you wanted.

- Awesome. Thank you.

(piano flourish)

- So how do we design a
system for billions of devices

to find any one of billions
of different websites?

There is no way one DNS server

can handle all of the
requests from all devices.

The answer is that DNS
servers are connected

in a distributed hierarchy,
and are divided into zones,

splitting up responsibility
for the major domains

such as .org, .com, .net, et cetera.

DNS was originally created to be

an open and public communication protocol

for government and
educational institutions.

Because of its openness,

DNS is susceptible to cyber attacks.

An example attack is DNS spoofing.

That's when a hacker
taps into a DNS server

and changes it to match a domain name

with the wrong IP address.

This lets the attacker send
people to one imposter website.

If this happens to you,

you are vulnerable for more problems

because you are using that
fake website as if it is real.

The internet is huge, and
getting bigger every day.

But the Domain Name System
and Internet Protocol

are designed to scale,

no matter how much the internet grows.