[Script Info]
Title: 
[Events]
Format: Layer, Start, End, Style, Name, MarginL, MarginR, MarginV, Effect, Text
Dialogue: 0,0:00:10.19,0:00:13.94,Default,,0000,0000,0000,,Hi! My name is Paola,and I am a software engineer at Microsoft.
Dialogue: 0,0:00:13.94,0:00:20.13,Default,,0000,0000,0000,,Let's talk about how the internet works. My job relies on networks being able
Dialogue: 0,0:00:20.13,0:00:26.49,Default,,0000,0000,0000,,to talk with one another, but back in the 1970s there was no standard method for this.
Dialogue: 0,0:00:26.49,0:00:32.67,Default,,0000,0000,0000,,It took the work of Vint Cerf and Bob Kahn to invent the internetworking protocol, to make communication possible.
Dialogue: 0,0:00:32.67,0:00:38.56,Default,,0000,0000,0000,,This invention laid the groundwork for what we now call the internet.
Dialogue: 0,0:00:38.56,0:00:44.47,Default,,0000,0000,0000,,The internet is a network of networks. It links billions of devices together all
Dialogue: 0,0:00:44.47,0:00:51.23,Default,,0000,0000,0000,,around the globe. So maybe you're connected with a laptop or a phone through wifi, then
Dialogue: 0,0:00:51.23,0:00:56.100,Default,,0000,0000,0000,,that wifi connection connects to an internet service provider (or ISP), and that ISP connects
Dialogue: 0,0:00:56.100,0:01:01.60,Default,,0000,0000,0000,,you to billions and billions of devices around the world through hundreds of thousands of
Dialogue: 0,0:01:01.60,0:01:03.27,Default,,0000,0000,0000,,networks that are all interconnected.
Dialogue: 0,0:01:05.60,0:01:15.67,Default,,0000,0000,0000,,One thing that most people do not appreciate is that the internet is really\Na design philosophy and an architecture expressed in a set of protocols.
Dialogue: 0,0:01:15.64,0:01:20.30,Default,,0000,0000,0000,,A protocol is a well known set of rules and standards, that if all parties
Dialogue: 0,0:01:20.30,0:01:26.30,Default,,0000,0000,0000,,agree to use it will allow them to communicate without trouble.
Dialogue: 0,0:01:26.30,0:01:31.91,Default,,0000,0000,0000,,How the internet actually physically works is less important than the fact that this design philosophy
Dialogue: 0,0:01:31.91,0:01:37.71,Default,,0000,0000,0000,,has allowed the internet to adapt and absorb new communication technologies.
Dialogue: 0,0:01:37.71,0:01:42.61,Default,,0000,0000,0000,,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.
Dialogue: 0,0:01:42.61,0:01:49.14,Default,,0000,0000,0000,,All the different devices on the internet have unique addresses.
Dialogue: 0,0:01:49.14,0:01:54.35,Default,,0000,0000,0000,,An address on the internet is just a number, similar to a phone number or a sort of street address,
Dialogue: 0,0:01:54.35,0:02:00.17,Default,,0000,0000,0000,,that's unique to each computer or device at the edge of the network.
Dialogue: 0,0:02:00.17,0:02:04.69,Default,,0000,0000,0000,,This is similar to how most homes and businesses have a mailing address. You don't need to know a person to
Dialogue: 0,0:02:04.69,0:02:09.11,Default,,0000,0000,0000,,send them a letter in the mail, but you do need to know their address and how to write
Dialogue: 0,0:02:09.11,0:02:14.19,Default,,0000,0000,0000,,the address properly so the letter can be carried by a mail system to its destination.
Dialogue: 0,0:02:14.19,0:02:19.87,Default,,0000,0000,0000,,The addressing system for computers on the internet is similar and it forms part of one
Dialogue: 0,0:02:19.87,0:02:25.34,Default,,0000,0000,0000,,of the most important protocols used in internet communication simply called the internet protocol or IP.
Dialogue: 0,0:02:25.34,0:02:31.89,Default,,0000,0000,0000,,A computer's address then is called its IP address. Visiting a website is really
Dialogue: 0,0:02:31.90,0:02:36.62,Default,,0000,0000,0000,,just your computer asking another computer for information. Your computer sends a message
Dialogue: 0,0:02:36.62,0:02:41.28,Default,,0000,0000,0000,,to the other computer's IP address and it also sends along its origin address, so the
Dialogue: 0,0:02:41.28,0:02:48.45,Default,,0000,0000,0000,,other computer knows where to send its response.
Dialogue: 0,0:02:46.28,0:02:49.45,Default,,0000,0000,0000,,You may have seen an IP address.It's just a bunch of numbers!
Dialogue: 0,0:02:49.45,0:02:50.91,Default,,0000,0000,0000,,These numbers are organized in a hierarchy.
Dialogue: 0,0:02:54.91,0:03:02.27,Default,,0000,0000,0000,,Just like a home address has a country, a city, a street, and a house number,
Dialogue: 0,0:03:02.27,0:03:09.52,Default,,0000,0000,0000,,an IP address has many parts. Just like all digital data, each of these numbers is represented in bits.
Dialogue: 0,0:03:09.52,0:03:14.47,Default,,0000,0000,0000,,Traditional IP addresses are 32 bits long, with 8 bits for each part of the address.
Dialogue: 0,0:03:15.52,0:03:18.47,Default,,0000,0000,0000,,The earlier numbers usually identify the country and regional network of the device.
Dialogue: 0,0:03:18.97,0:03:22.47,Default,,0000,0000,0000,,Then come the subnetworks, and then finally the address of the specific device.
Dialogue: 0,0:03:22.47,0:03:30.47,Default,,0000,0000,0000,,This version of IP addressing is called IPv4.
Dialogue: 0,0:03:30.47,0:03:34.05,Default,,0000,0000,0000,,It was designed in 1973 and was widely adopted in the early 80s,
Dialogue: 0,0:03:30.47,0:03:38.05,Default,,0000,0000,0000,,and provides for more than 4 billion unique addresses for devices connecting to the internet.
Dialogue: 0,0:03:40.42,0:03:47.34,Default,,0000,0000,0000,,But the internet has turned out to be much more popular than even Vint\NCerf imagined and 4 billion unique addresses won't be enough.
Dialogue: 0,0:03:47.34,0:03:53.26,Default,,0000,0000,0000,,We're now in the middle of a multi-year transition to a longer IP address format
Dialogue: 0,0:03:53.26,0:04:03.66,Default,,0000,0000,0000,,called IPv6, which uses 128 bits per address and provides over 340 undecillion unique addresses.
Dialogue: 0,0:04:03.66,0:04:08.78,Default,,0000,0000,0000,,That's more than enough for every grain of sand on Earth to have its own IP address.
Dialogue: 0,0:04:08.78,0:04:15.74,Default,,0000,0000,0000,,Most users never see or care about internet addresses.
Dialogue: 0,0:04:15.74,0:04:23.41,Default,,0000,0000,0000,,A system called the domain name system or DNS associates names like www.example.com with the corresponding addresses.
Dialogue: 0,0:04:23.41,0:04:29.16,Default,,0000,0000,0000,,Your computer uses the DNS to look up domain names and get the associated IP
Dialogue: 0,0:04:29.16,0:04:33.29,Default,,0000,0000,0000,,address which is used to connect your computer to the destination on the internet.
Dialogue: 0,0:04:33.29,0:04:38.05,Default,,0000,0000,0000,,And it goes a little something like this: (voice1) "Hey, hi there, I want to go to www.code.org."
Dialogue: 0,0:04:38.05,0:04:49.90,Default,,0000,0000,0000,,(voice 2) "Mm.. yeah I don't know the IP address for that domain let me ask around.\NHey, do you know how to get to code.org?"
Dialogue: 0,0:04:49.90,0:04:59.10,Default,,0000,0000,0000,,(voice 3) "Yeah, I got it right here it's 174.129.14.120."
Dialogue: 0,0:04:59.10,0:05:04.50,Default,,0000,0000,0000,,(voice 2) "Oh okay, great, thanks. I'm gonna write that down and save it for later in case I need it again.
Dialogue: 0,0:05:04.50,0:05:14.04,Default,,0000,0000,0000,,Hey here's that address you wanted." (voice 1) "Awesome! Thank you."
Dialogue: 0,0:05:14.04,0:05:20.12,Default,,0000,0000,0000,,So how do we design a system for billions of devices to find any one of billions of different websites?
Dialogue: 0,0:05:20.12,0:05:27.89,Default,,0000,0000,0000,,There is no way one DNS server can handle all the requests from all devices.
Dialogue: 0,0:05:27.89,0:05:33.00,Default,,0000,0000,0000,,The answer is that DNS servers are connected in a distributed hierarchy, and are divided into zones,
Dialogue: 0,0:05:33.00,0:05:40.70,Default,,0000,0000,0000,,splitting up responsibility for the major domains such as .org, .com, .net, etc.
Dialogue: 0,0:05:40.70,0:05:48.03,Default,,0000,0000,0000,,DNS was originally created to be an open and public communication protocol for government
Dialogue: 0,0:05:48.03,0:05:55.37,Default,,0000,0000,0000,,and educational institutions. Because of its openness, DNS is susceptible to cyber attacks.
Dialogue: 0,0:05:55.37,0:06:02.54,Default,,0000,0000,0000,,An example attack is DNS spoofing. That's when a hacker taps into a DNS server and changes
Dialogue: 0,0:06:02.54,0:06:09.48,Default,,0000,0000,0000,,it to match a domain name with the wrong IP address. This lets the attacker send people to an imposter website.
Dialogue: 0,0:06:09.48,0:06:15.74,Default,,0000,0000,0000,,If this happens to you, you are vulnerable for more problems
Dialogue: 0,0:06:15.74,0:06:23.87,Default,,0000,0000,0000,,because you are using that fake website as if it's real. The internet is huge and getting bigger everyday.
Dialogue: 0,0:06:23.87,0:06:30.79,Default,,0000,0000,0000,,But the domain name system and internet protocol are designed to scale,
Dialogue: 0,0:06:30.79,0:06:35.21,Default,,0000,0000,0000,,no matter how much the internet grows.