00:00How does the internet work? The video you are watching now traveled thousands of
00:07miles from a Google data center to reach you. Let's learn how the internet works
00:13by getting to understand the details of this data's incredible journey. The data
00:21center, which can be thousands of miles away from you, has your video stored
00:25inside it. How does this data reach your mobile phone or laptop? An easy way to
00:32achieve this goal would be with use of satellites. From the data center, a signal
00:37could be sent to the satellite via an antenna.
00:42And then from the satellite, a signal could be sent to your mobile phone via
00:46another antenna near to you. However, this way of transmitting signals is not a good
00:51idea. Let's see why. The satellite is parked nearly 22,000 miles above the
00:58Earth's equator. So in order for the data transmission to be successful, the data
01:03would have to travel a total distance of 44,000 miles. Such a long distance of
01:08travel causes a significant delay in receiving the signal. More specifically,
01:12it causes huge latency, which is unacceptable for most internet applications. So if this
01:18video does not reach you via a satellite, then how does it actually get to you? Well,
01:23it is done with the help of a complicated network of optical fiber cables, which
01:28connect between the data center and your device.
01:33Your phone could be connected to the internet via cellular data or any Wi-Fi
01:37router. But ultimately, at some point, your phone will be connected to this network of
01:42optical fiber cables. We saw at the beginning that the video you are currently watching is
01:50stored inside a data center. To be more specific, it is stored in a solid state device within
01:57the data center. This SSD acts as the internal memory of a server. The server is simply a powerful
02:04computer whose job is to provide you the video or other stored content when you request it.
02:10Now, the challenge is how to transfer the data stored in the data center specifically to your device via
02:16the complex network of optical fiber cables. Let's see how this is done. Before proceeding further,
02:23we should first understand an important concept, which is the concept of an IP address. Every device
02:29that is connected to the internet, whether it is a server, a computer, or a mobile phone, is identified
02:35uniquely by a string of numbers known as an IP address. You can consider the IP address similar
02:43to your home address. That is, the address that uniquely identifies your home. Any letter sent to
02:50you reaches you precisely because of your home address. Similarly, in the internet world, an IP address
02:58acts as a shipping address through which all information reaches its destination. Your internet
03:04service provider will decide the IP address of your device, and you are able to see what IP address your
03:10isp has given to your mobile phone or laptop. The server in the data center also has an IP address.
03:20The server stores a website, so you can access any website just by knowing the server's IP address.
03:26However, it is difficult for a person to remember so many IP addresses. So to solve this problem, domain names
03:33like youtube.com, facebook.com, etc., are used which correspond to IP addresses, which are easier for us
03:41to remember than the long sequence of numbers. Another thing to notice here is that a server has the
03:46capability of storing several websites, and if the server consists of multiple websites, all the websites
03:53cannot be accessed with the server's IP address. In such cases, additional pieces of information,
03:59host headers are used to uniquely identify the website. However, for the giant websites like facebook.com or
04:06youtube.com, the entire data center infrastructure will be dedicated to the storage of the particular website.
04:14To access the internet, we always use domain names instead of the complex IP address numbers.
04:20From where does the internet get IP addresses corresponding to our domain name requests?
04:25Well, for this purpose, the internet uses a huge phone book known as DNS. If you know a person's name
04:33but
04:33don't know their telephone number, you can simply look it up in a phone book. The DNS server provides the
04:39same service to the internet. Your internet service provider or other organizations can manage the DNS server.
04:49Let's have a recap of the whole operation. You enter the domain name. The browser sends a request to the
04:55DNS server to get the corresponding IP address. After getting the IP address, your browser simply forwards the
05:02request to the data center, more specifically to the respective server. Once the server gets a request to access a
05:11particular website, the data flow starts. The data is transferred in digital format via optical fiber cables, more
05:18specifically in the form of light pulses. These light pulses sometimes have to travel thousands of
05:24miles via the optical fiber cable to reach their destination. During their journey, they often have
05:30to go through tough terrains such as hilly areas or under the sea. There are a few global companies who
05:37lay
05:37and maintain these optical cable networks. These visuals show how the laying of optical fiber cables is done
05:44with the help of a ship. A plow is dropped deep into the sea from the ship. And this plow
05:53creates a trench
05:54on the seabed into which is placed the optical fiber cable. In fact, this complex optical cable network is the
06:02backbone of the internet. These optical fiber cables carrying the light are stretched across the seabed to
06:09your doorstep, where they are connected to a router. The router converts these light signals to electrical
06:16signals. An ethernet cable is then used to transmit the electrical signals to your laptop. However, if you
06:25are accessing the internet using cellular data, from the optical cable the signal has to be sent to a cell
06:31tower. And from the cell tower, the signal reaches your cell phone in the form of electromagnetic waves.
06:40Since the internet is a global network, it has become important to have an organization to manage
06:46things like IP address assignment, domain name registration, etc. This is all managed by an
06:52institution called ICANN, located in the USA. One amazing thing about the internet is its efficiency
06:59in transmitting data when compared with cellular and landline communication technologies.
07:04This video you are watching from the Google Data Center is sent to you in the form of a
07:09huge collection of zeros and ones. What makes the data transfer in the internet efficient is the way
07:15in which these zeros and ones are chopped up into small chunks, known as packets, and transmitted.
07:21Let's assume these streams of zeros and ones are divided into different packets by the server,
07:26where each packet consists of six bits. Along with the bits of the video, each packet also consists of the
07:34sequence number and the IP addresses of the server and your phone. With this information,
07:40the packets are routed towards your phone. It's not necessary that all packets are routed through the
07:46same path, and each packet independently takes the best route available at that time. Upon reaching your
07:52phone, the packets are reassembled according to their sequence number. If it is the case that any packets
07:58fail to reach your phone, an acknowledgement is sent from your phone to resend the lost packets.
08:04Now compare this with a postal network with a good infrastructure, but the customers do not follow
08:10the basic rules regarding the destination addresses. In this scenario, letters won't be able to reach the
08:16correct destination. Similarly in the internet, we use something called protocols for the management of
08:24this complex flow of data packets. The protocols set the rules for data packet conversion, attachment
08:30of the source and destination addresses to each packet, and the rules for routers, etc. For different
08:36applications, the protocols used are different. We hope this video has given you a good understanding
08:43about how the internet works. More specifically, about the amazing journey of data packets from the data
08:50center to your mobile phone. Please don't forget to support us at patreon.com. Thank you.
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