A few months ago, I was relaxing with my girlfriend in our living room while she was scrolling through a huge list of clothes from Zara’s e-commerce site, as she frequently does. Suddenly, she asked me,
"Why aren’t the X and Y t-shirts available online? I saw them in the store a week ago."
I replied, "Well, maybe they’re just not available anymore."
To my surprise, she said, "Or they forgot to throw it in the air." I responded, "In the air?" She said, "Yeah, you know, on the internet."
This comment stuck in my mind for a while. Internet? In the air? So, I asked her:
"What comes to your mind when we talk about the Internet? Like, how do you imagine the internet works?"
"In the air, like, I don’t know, for me, the internet works like the air. We just have everything floating in the air. Like when we use the wifi and then we are getting all the things from the air…I have no idea"
That small talk took me back to my university days when I was studying computer networks (honorable mention to my teacher Jeyniglis), and I was struggling to understand the OSI layers!
Well, let's start at the beginning: what is the internet? For me, the best answer is well cited in the book "Computer Networks: A Top-Down Approach" by Kurose.
”The Internet is a network of networks!”
This sentence will make more and more sense as we start to understand how networks work and how they connect with each other.
Ok, let’s imagine the hypothetical scenario below:
You are in your house with two friends, and you are using computers. Each computer is connected to the other through a cable. Using this cable, you can send data to your friends, and vice versa.
With the scenario above, you can send data (you can imagine data as images, for example) from PC A to PC B or from PC C to PC A. It is possible because you are physically connected by a cable, and through this cable, you can send whatever you want. This very simple example can be considered a computer network! I would say that we need to meet at least three main goals to be able to consider a computer network:
1 - Interconnection: The three computers are physically connected to each other, allowing communication and data exchange.
2 - Data Exchange: The ability to send and receive data between the computers is an essential element of any network.
3 - Network Definition: A computer network is defined by the interconnection of devices that allow communication between them, regardless of whether they are connected to the public internet or not. (We will understand the concept of the public internet later.)
Ok, perfect! Now we have clear in our minds the concept of computer networks. And this very tiny example has a name: Local Area Network or LAN.
A small definition of LAN
"A Local Area Network (LAN) is a computer network that spans a relatively small geographical area, typically confined to a single building or a campus. LANs are characterized by high data transfer rates, small geographic scope, and lack of reliance on leased telecommunication lines."
Nice, with our LAN, we now have our first simple image in our minds of a computer network. Let’s imagine a new scenario:
Now, we want to send and receive data to another group of friends. But the problem is, they are very, very far away from our house (1000 km away). So, to be able to connect with them, should we buy a very powerful and large cable to connect our houses? Well, maybe you can try if you have enough money to build an infrastructure to support this sort of operation.
The first problem with the method above that we can start to think about is:
1 - do we need to use a cable for each computer?
It starts to become chaotic very quickly, right? For this scenario, we would need at least 15 cables to be able to connect each computer physically.
To solve this problem, let’s imagine that we have a machine that can serve as a point of connection for all devices in our LAN (Lets call it as POC). Now, instead of having three cables for each computer, we just need to connect each computer to this new device, and with this, you are now connected with all devices also connected to this point-of-connection machine. With this approach, it becomes pretty easy. Now, we just need one very ultra-large cable to connect our new machine with another machine in another place in the world that also has a LAN connected to it. In our example, a house of our friends that are 1000 km away from us.
Does this sound familiar to you? It probably does because if you’re reading this article, you likely have a machine like this in your house. This "point of connection" machine is actually called a modem! You've probably noticed it in your living room. Remember when a technician knocked on your door some time ago, saying they needed to install this box to give you internet access? And every time your internet isn’t working as expected, the first thing you usually try is restarting this little device.
Ok, now we solve the problem that we have of conect all machines with a modem. But now, we still continuing have a huge problem…
2 - How can we connect this modem through 1000 km away to our friend's house?
I have good news for you. You don't need to do this yourself. You just need to pay a company to handle it for you. That's right, there are companies with extensive infrastructure that includes various types of cables, such as fiber optic cables or coaxial cables, that span large geographical areas in your city.
These companies, often Internet Service Providers (ISPs) or telecom companies, have invested in the necessary technology and infrastructure to ensure reliable and high-speed connections over long distances. They have a network of data centers, routers, switches, and cables that interconnect cities and even countries.
When you subscribe to their services, they use their infrastructure to connect your modem to their network, regardless of the distance. They take care of the complex routing, signal boosting, and maintenance required to keep the connection stable and fast. This way, you can enjoy seamless internet access without having to worry about the technical challenges of long-distance connectivity.
In summary, simply contact a reputable and good ISP, choose a suitable plan, and they will manage the entire process of connecting your modem to their network, ensuring you stay connected no matter the distance.
Understanding the Three Levels of ISPs
ISPs (Internet Service Providers) are categorized into three levels based on their role and reach within the global internet infrastructure. These levels are Tier 1, Tier 2, and Tier 3. Each level serves a specific function and plays a crucial role in ensuring seamless global connectivity. Here’s a detailed description of each:
Tier 3 ISPs:
Description: These are your friendly neighborhood ISPs. They’re the ones you deal with directly when you sign up for internet service at home or at your small business. They buy access from Tier 2 (and sometimes Tier 1) ISPs.
Services: They provide internet services to end-users, like you and me. They handle everything from installation to customer support ( the guy who knock your door…)
Importance: Tier 3 ISPs are essential because they bring the internet right to our doorsteps, making sure we can stream, game, and browse without a hitch.
Tier 2 ISPs:
Description: Tier 2 ISPs are like the middle managers. They buy access from Tier 1 ISPs and also make deals (called peering) with other ISPs. They cover large regions but don’t have the same global reach as Tier 1.
Services: They connect regional networks and serve as a bridge between Tier 3 ISPs and the global internet. They help data move from local networks to the wider world.
Importance: Tier 2 ISPs play a crucial role in expanding internet access beyond the major hubs, ensuring regional connectivity.
Tier 1 ISPs:
Description: Think of Tier 1 ISPs as the big bosses of the internet world. They own massive networks that span continents and connect entire countries. These guys don’t have to pay anyone to access the global internet; they’re already at the top.
Services: They offer direct access to the internet backbone and make deals with other Tier 1 ISPs to keep data flowing smoothly across the planet.
Importance: Without Tier 1 ISPs, the internet wouldn’t be able to function on a global scale. They ensure that data can travel long distances efficiently.
Now that we know about ISPs, we understand that we don't need to connect a physical cable that runs from our house and travels 1000 km across the world to reach another country and plug into a friend's house. Instead, we use the entire infrastructure of ISPs. It's simple: first, we hire a Tier 3 ISP. They send someone to install a modem in our home, and a cable runs from that modem to the infrastructure of the ISP we hired.
This Tier 3 ISP is connected to a larger infrastructure of a Tier 2 ISP (Or Tier 1), which has a broader reach. The Tier 2 ISP, in turn, pays for the services of a Tier 1 ISP, which has cables crossing continents under the oceans. This way, our local connection integrates into a global communication network, allowing us to connect with someone on the other side of the world without the need for a direct physical cable all the way there.
With the explanation above, our cenario is more similar to this:
Remember when I said at the beginning that the best definition of the internet is "a network of networks"? Well, this is the reason why. In the end, we have various networks interconnected by these companies, and when we piece them all together, we get what we now call the internet.
Small summary and conclusion
Instead of having to connect a physical cable from your house and stretch it 1000 km across the world to another country to reach a friend's house, we use the infrastructure of ISPs. First, we hire a Tier 3 ISP. They send someone to install a modem at our place, and a cable runs from that modem to the infrastructure of the ISP we hired.
Here's where the magic happens: this Tier 3 ISP is connected to a larger infrastructure of a Tier 2 ISP, which has an even broader reach. And this Tier 2 ISP pays for the services of a Tier 1 ISP, which has cables crossing continents under the oceans. This way, our local connection integrates into a global communication network.
In the end, each of these ISPs has its own networks, and when they interconnect, they form the vast network we know as the internet. That's why we call the internet "a network of networks." It's this combination of many smaller interconnected networks that allows us to be connected with someone on the other side of the world without needing a direct physical cable all the way there. And it's this collaboration that keeps the internet running, letting us do everything from streaming videos to video chatting with friends anywhere on the planet.
Of course, this is just a summary and barely scratches the surface of the complexity of the internet. There are many other pieces of equipment and technologies involved, such as routers, switches, DNS servers, communication protocols like TCP/IP, and network management systems that play crucial roles in maintaining and operating the internet.
For those who want to delve deeper into how all this works and understand all the key components that make this network possible and functional, we highly recommend reading "Computer Networking: A Top-Down Approach" by James F. Kurose and Keith W. Ross. This book provides a detailed and comprehensible look into the fundamentals of computer networks and the complexity of the internet.
