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Angela: Hey guys, it's Angela from The App Brewery

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and in this lesson we're gonna deep dive

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into how exactly does the internet work.

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So what exactly is the internet?

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A lot of people think it's a cloud

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something that's hanging around in the sky.

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It's super complex, super difficult to understand

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but actually that's not it at all.

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The internet is pretty simple.

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All it is is just a long piece of wire.

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And the wire connects different computers to each other.

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So you might have one computer that's in London

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and another one that's in Seattle, and they can talk

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to each other and transfer data through this giant wire.

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Now, some of these computers attached

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to the internet have a very special job.

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They have to be online 2/7, ready to serve you all the data

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and files that you are requesting when you try to

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access a website.

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And these are called servers.

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And what they do is they serve you all the data

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and files you need to be able to access

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and interact with certain websites.

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So these computers are called servers.

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And any computer that a user would use to

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access the internet is called a client.

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Now, you can imagine a web server

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as a giant library that's open 24/7

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and you can go in there at any hour

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of the day and say, I wanna see Google's homepage

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or I wanna see the latest posts on TechCrunch.

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And it would be able to serve you

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with all the files and data you would need to

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be able to view whatever website you want.

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Now, as you can imagine

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if there's a library that's big enough to house all

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of these websites, then it's gonna be pretty

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difficult to quickly locate the thing that you want

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out of this giant library, right?

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So how is this problem solved on the internet?

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Well, let's say that you're sitting at home

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on your computer and you type in google.com

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because you wanna head over to the main Google homepage.

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Well, what happens behind the scenes is

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that your browser will send that message

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to your ISP or your internet service provider.

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So these are the people who you pay to be able to

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access the internet.

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If you live in the US, that will be AT&T or Comcast.

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And if you're in the UK,

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it'll be something like BT or TalkTalk.

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Now, the message that you're sending the ISP

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is I wanna see google.com

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and the ISP will then relay that message

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to something called a DNS server

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which stands for a domain name system server.

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And a DNS server is essentially just a souped up phone book.

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And what happens when you make that request

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through your browser is the DNS server will look

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up in its database to find the exact IP address

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of that website that you're trying to access.

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And every single computer that's connected

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to the internet has an IP address.

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It's kind of like a postal code for your computer

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so that when people need to send and receive files

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on the internet, each computer can be located

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and contacted using their unique IP address.

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And once the DNS server finds that IP address

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it'll send it back to your browser

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through the ISP over the internet.

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Then you can make a direct request

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to that address and what lives

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that that IP address is, of course the Google servers

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and they'll be able to send you back all the files

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and data you need to be able to view the Google homepage.

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Now, you can try this for yourself to look

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up the IP address of the Google homepage, head

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over to this website, NSlookup.io, and type in google.com

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and they should show you the exact IP address

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of the Google servers that you can access.

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Now, if you try checking this

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on a different day, say in a week or in a month's time,

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you might see that this address actually changes.

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And that's because many websites including Google

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use something called Dynamic IP addresses as well

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as a content distribution network or a CDN.

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This basically ensures that it gets you

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to the closest server to where you are located.

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And also this address will change depending

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on whether if it's being used or not.

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So don't type in what you see on screen.

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Instead, head over to NSlookup.io

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and look up what is the closest IP address

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to you that is currently being used.

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So if you copy it and paste it into a new tab

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then you'll be able to replicate that process

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and see the Google Homepage show up.

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So to summarize, the internet is just a bunch

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of wires that connects up different computers, but it's just

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on a much bigger scale connecting

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up all the computers in the world.

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But what about the oceans I hear you ask.

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Well, that's one of the coolest things.

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There are these massive undersea cables

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connecting all the continents on earth.

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And if you head over to submarinecablemap.com

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you can see all of these cables

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and see the ones that connect you up to the internet.

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And these undersea cables are massive consisting of hundreds

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of fiber optic fibers, each of them using lasers to transmit

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up to 400 gigabytes of data per second.

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This is a cross section of one

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of the cables that run to New Zealand.

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It's an absolute marvel of modern technology

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and it looks really beautiful, don't you think?

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And to think that every single time we load up a webpage

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or click on a button on a website, behind the scenes

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we're sending signals that navigates all

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of this crazy underwater and above water wires.

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And all I need is just an IP address.

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And through tiny electric signals traveling

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at the speed of light through the oceans

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and halfway around the world, in a matter of milliseconds

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I get to view my favorite websites.

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And that is how awesome the internet is.

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And we're gonna be taming it to build our own websites

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and web apps.

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And to be able to do that

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we first have to understand how exactly do websites work.

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So for all of that and more,

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I'll see you on the next lesson.