How does the Internet work?

          How does the data arrive on your mobile phone or computer? 

   
   
     The article you're reading right now has traveled thousands of miles from a google data center to get to you. We're going to see how the internet works and we'll find out the details of the fascinating journey of this data.

     A data center, which can be thousands of miles away from your home, hosts the content you've created.
       
     An easy way to achieve this would be to use satellites, from the data center a signal can be sent to the satellite via an antenna, then from the satellite, a signal can be sent to your mobile phone via another antenna near you, however, this way of transmitting signals is not a good idea.

     The satellite in orbit is about 35400 Km or 22000 miles above the earth's equator, so in order for data transmission to go smoothly, the data would have to travel a total distance of 70800 Km or 44000 miles, such a travel distance causes a significant delay in signal reception, more precisely it causes a huge latency, which is unacceptable for most internet applications.

     If this content doesn't reach you via satellite, then how? It's done through a complex network of fiber optic cables, which connects the data center is your device. 

     Your phone can be connected to the internet via cellular data or any wifi router, but at some point, your phone will be connected to this fiber optic cable network.

     The item you are reading now, is stored in a data center, to be more precise, it is stored on a storage device in the SSD datacenter, this SSD acts like the internal memory of a server.

     The server is simply a powerful computer, whose task is to send you the stored content when you request it, the most difficult task now is to transmit the data stored in the datacenter, especially to your device via the complex network of fiber optic cables.

          The basic principle of how an IP address works

      Every device connected to the Internet, whether a server, computer or mobile phone, is uniquely identified by a string of numbers called IP addresses.

     You could consider the IP address similar to the address of your home, that is the address that uniquely identifies your residence, all letters that are sent to you, reach you precisely because of your postal address, similarly on the Internet an IP address cert address for the delivery of all information to their destination.

     Your internet service provider will decide the IP address of your device, and you can see which IP address your internet service provider has assigned to you for your mobile phone, or your laptop by writing on the google search bar the keyword "my IP address".

     The server in the data center also has an IP address, the server hosts a website, which means that you can access any website simply by knowing the IP address of the server, however, it is difficult for a person to remember so many IP addresses.

     In order to solve this problem, domain names, such as youtube.com, facebook.com, etc, are used to match IP addresses, thus making it easier for us to remember names than long sequences of domain numbers.

     It should also be noted that a server has the capacity to store several websites, and if the server hosts several websites, not all websites can be accessed with the IP address of the server, in such cases additional information, host headers are used to uniquely identify the website, however for gigantic sites like facebook.com or youtube.com, the entire infrastructure of the data center will be dedicated to storing the site in question, to access the internet we always use domain names instead of complex IP addresses.

           Where do the IP addresses corresponding to the domain name come from?

     For this, the internet uses a huge phone book, known as DNS, if you know a person's name, but you don't know their phone number, you can simply find it in a phone book, the DNS server provides the same service for the internet, your internet service provider or other organizations can manage the DNS server.

     Let's summarize the whole operation, you enter the domain name, the browser sends a request to the DNS servers to obtain the corresponding IP address, after obtaining the IP address, your browser simply transmits the request to the data center, more specifically to the servers involved, once the server receives a request to access a particular website, the data flow starts.

     The data is transferred in digital format via fiber-optic cables, more precisely in the form of light impulses. 

     These light impulses sometimes have to travel thousands of kilometers via the fiber-optic cable to reach their destination.

     During their journey, they often have to cross difficult terrains, such as mountainous regions or the seabed. Some international companies, such as AT&T, Orange, Verizon Google, lay and maintain these optical cable networks.

      The laying of fiber optic cables is done using specialized vessels, a blade is thrown deep into the sea from the vessel, and this blade creates a trench on the seafloor, in which the fiber optic cable is placed, in fact, this complex optical cable network is the backbone of the Internet network, These fiber optic cables, which carry light, are laid out on the seabed and underground to your doorstep, where they are connected to a router. 

     The router converts the light signals into electrical signals, an Ethernet cable is then used to transmit the electrical signals to your computer.

     However, if you access the internet using cellular data, the signal must be sent from the optical cable to a cell phone tower, and from there the signal reaches your mobile phone as an electromagnetic wave.

     Since the internet is a global network, it has become important to have an organization to manage things like IP address assignment, domain name registrations, etc.

     All this is managed by an institution called ICANN "Internet Corporation For Assigned Names And Numbers" located in the United States. One of the most remarkable things about the internet, and its efficiency in data transmission, compared to cellular and terrestrial communication technologies.

     This article that you are reading from google's datacenter, is sent to you like a huge amount of 0 and 1.

     What makes data transfer over the Internet efficient is the way these 0s and 1s are cut into small pieces, called a packet, and then delivered.

     Suppose these streams of 0s and 1s are divided into different packets by the server, where each packet consists of 6 bits, in addition to the bits of the article, each packet also includes the sequence number and the IP addresses of the server and your phone. 

     With this information the packets are routed to your phone, it is not necessary for all packets to go through the same path, and each packet independently takes the best path available at that time.

     When packets arrive on your phone, they are reassembled according to their sequence number, if packets do not reach your phone, an acknowledgment is sent by your phone, to return lost packets.

     Compare this with a postal network with good infrastructure, but with clients that do not follow the basic rules regarding destination addresses.

     In this scenario the letters will not be able to reach the right destination, also on the internet, we use so-called protocols to manage this complex flow of data packets.

     Protocols define the rules for converting data packets, attaching source and destination addresses to each packet, rules for routers, etc, for different applications the protocols used are different.

     This is how the internet works, especially the extraordinary journey of data packets from the data center to your smartphone or computer.

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