Imagine waking up with a start and suddenly you are in the 1930s. You have no internet, no network signal, no phone and, of course, no social media. Now you can’t even tweet about your current predicament. All you can do is try to survive whatever the 1930s was like in your country.

That doesn’t sound very fun, does it? It’s weird to imagine a life without the internet but there was once a life without it. Have you ever wondered how we got here? How do our devices connect to the internet? How do we text and stream videos with no physical connection? Well, me too!

History of the Internet

It all began in the 1960s. The Soviet Union and the United States both wanted to be the first to launch the first Satellite. However, the Soviet Union won, launching the Sputnik satellite before the U.S. could. This later spurred the U.S.'s creation of the Advanced Research Projects Agency Network (ARPANET) during the cold war between the U.S. and the Soviet Union so that they wouldn't miss out entirely on being the "first" to do something.

ARPANET was built for sharing information using the Transfer Control Protocol (TCP). This protocol is the set of rules governing the transmission of data, but as it evolved, a new communication protocol was established called Transfer Control Protocol/Internet Protocol (TCP/IP). This lets different kinds of computers on various networks communicate with each other.

Your Device and the Internet

A network of networks is called internetwork, or simply the internet. It is a huge system of interconnected computer networks that uses the Internet Protocol Suite (TCP/IP) to communicate between networks and devices. It is the largest network in the world. Presently, the Internet is implemented using IPv4 because of the need for more IP address spaces, however, it is migrating from IPv4 to IPv6. The Internet helps its users share and access a huge amount of information globally. It uses WWW, FTP, email services, audio and video streaming etc.

What Happens When You Search on Google?

• Your PC is connected through a modem and/or router. Your router enables many computers to join the same network while a modem connects to your Internet Service Provider (ISP) which provides you with either cable or Digital Subscriber Line/Loop (DSL) internet.

• On Google, after typing in a web address, also known as Uniform Resource Locator (URL), your query is pushed to your ISP.

  Note: your ISP has a record of every site you visit, it doesn't matter if you turn on incognito mode or not.

• The Domain Name System (DNS) then translates the text-based domain name you typed into the number-based IP address. For instance: google.com becomes 173.194.215.138

• If the IP address of the website is not in the ISP cache, the DNS initiates a DNS query to find the IP address of the server that hosts the domain name.

• When it’s found, your browser initiates a connection using TCP/IP, and then it sends a Hypertext Transfer Protocol (HTTP) request to the target server to send a copy of the website.

  Note: HTTP is an application layer protocol and it is one of the TCP/IP protocols. This is part of the network communication of the TCP/IP, there would be a further explanation of this as you read on.

• The server approves the request and sends a status code “200 OK” message to your computer. Then, the server sends website files to the browser in the form of data packets.

• As your browser reassembles the data packets, the website loads.

• Your search results are now available!

Network Communication

Network communication is a set of protocols i.e. rules that allow application programs to communicate with each other independently of their hardware and operating system (hardware & OS agnostic). The Open Systems Interconnection (OSI) model is a reference model of network communication. It defines how data is encoded, formatted, encapsulated, and segmented so that it can be transmitted over networks, while TCP/IP is an implementation of the OSI model which helps you to determine how a specific computer should be connected to the internet and how data can be transmitted.

How data moves through the OSI model

The OSI Model is a reference and logical model that defines network communication used by systems open to interconnection and communication with other systems.

How this works;

• From the application layer, the message is received, passed and encrypted in the presentation layer.

• Then the session layer handles the network connection and authorization/authentication.

• The Transport layer deals with the transport of the message as data segments using either Transmission Control Protocol (TCP) or User Datagram Protocol (UDP).TCP is a connection-oriented protocol that ensures your data is delivered and maintains the order of data using the sequence number. On the other hand, UDP is a connectionless protocol, your data may or may not be delivered completely or in the correct order, but it is typically used because it’s faster.

• The network layer deals with the transmission of data. Its main function is to transfer data as packets from the source to the destination. It also manages data traffic problems such as switching, routing and congestion control.

• In the Data link layer, the data packets are broken into frames and sent to the physical layer. The physical layer is the lowest layer of the OSI reference model. The frames received from the datalink layer are broken into bits (binary data) for data transmission.

How does the TCP Model Work?

TCP/IP is a communication protocol/rule that determines how a specific computer should be connected to the internet and how data can be transmitted between them. TCP ensures that the transfer of data is dependable. It makes sure no packets are lost, no delay affecting the quality of data, and that packets are organized in the right order. IPs are the rules that control how information is sent from one computer to another over an internet connection.

• The application layer is the component that interfaces with the end user, this is the layer that the user directly interacts with when using internet services. For instance, sending an email.

• The transport layer defines the various ports and it differentiates the different activities from a single user. You may be surfing the internet, texting and listening to music on one computer. It is the work of the transport layer to differentiate these different activities and ensure that the data segments are sent or received in the same sequence as it was sent by the sender.

• The internet/network layer divides the data received from the transport layer in the form of packets. it controls the flow of data from source to destination, it is also concerned with reassembling data packets at their destination.

• The network access layer combines the physical & datalink layer of the OSI model. it handles the mechanics of how data is physically transmitted through the networks, which is how these signals (binary data) are transmitted through cables or airwaves.

Data Signal Transmission - How Are We Connected?

When we interact with the internet i.e. sending messages, streaming videos, surfing the web, etc. data is transmitted from the source to the destination. This is made possible by the transmission of data signals. Signals are the electric or electromagnetic current that is used to transmit data from one network to the other. This data can be transmitted through cables or airwaves referred to as Transmission Media.

Transmission Media are of two types:

• Guided Media

• Unguided Media

Guided Media

In Guided media, signals are transmitted through a narrow pathway using physical links. A good use case is the Submarine cable system. While we live in a seemingly wireless world, a significant part of that connectivity depends on underwater internet cables, known as submarine cables. These submarine cables are responsible for almost all international telecommunications traffic connecting different continents. They generally use optical fibre cables and carry most of the world’s cross-continent data traffic, they are the most valued cables for mega companies from Amazon to Google. You can see an overview of the submarine cable system here.

Unguided Media

It is referred to as Wireless or Unbounded transmission media. No physical medium is required for the transmission of electromagnetic signals. Its use cases are:

• For short ranges ⇒ Bluetooth and Wi-Fi

• For longer ranges ⇒ 3G, 4G LTE, 5G

Conclusion

In summary, when someone sends something over the internet, it goes from the application layer, the data is encapsulated then it leaves the physical layer, but, when someone receives something from the internet it comes from the physical layer and the data is decapsulated and it shows up on the application layer.

This is just a basic overview of computer networking. If you are interested in the mechanics of networking I encourage you to keep making research on the subject. It is very deep and extensive. If you have suggestions, corrections, questions or you learned something new, you can send in your comments, as I would like to know your thoughts.

Hope you found this article helpful! Cheers.