The Internet : Understanding computer networks and protocols involves learning about URLs, DNS, TCP, and UDP.
We all have computers, smartphones, tablets, smart TVs, and even smartwatches.
These gadgets can function independently and perform tasks. When you link them to the internet using a 5G/4G connection, a Wi-Fi network, or by connecting with an Ethernet cable, you gain access to the world outside.
Behind the scenes, when your device is linked to the internet, it gets assigned an IP address.
This address consists of four sets of numbers, ranging from 0 to 255. You can locate this number in your device’s network settings.
As an illustration, my MacBook’s IP address right now is 192.168.1.105. Addresses beginning with 192.168. are set aside for local networks. That means it’s part of your local network.
The local network is formed by your Wi-Fi or Ethernet router, which is connected to your internet provider.
Here’s how it works: the router links to the internet provider and gets its own IP address.
Afterward, the router establishes the local network and gives each connecting device a unique local IP address. This means every device in your home has a different IP address.
You can exchange information between devices on your local network, but it’s not possible to communicate with devices in other local networks, like the ones in your friend’s house, unless specific arrangements are made for this.
This protection is there because, in a local network, the IP address is private.
Our devices can send information to the internet whenever we want, but the internet can’t send information to our devices unless we specifically allow it and set up systems for that (and this is done on purpose, so we don’t have to worry about hackers trying to control our smart thermostat or something worse).
So, we can instruct our devices to communicate with something on the internet. Great! But… who do we communicate with?
The answer is other computers, known as servers.
A server is a computer with the job of providing us something.
Just like our devices, a server also has an IP address, but this time it’s public because the server is meant to be accessed, unlike our home devices. The server needs to be reachable all the time.
Apart from an IP address, a server also has a name, which we call a domain name.
There are other computers called DNS servers, and their job is to connect a domain name to an IP address. So instead of saying “visit 142.250.184.78,” we say “visit google.com.”
People find names easier to remember, while computers prefer numbers. DNS makes things simple for both.
Typically, you don’t try to access a website using its IP address. It’s possible, but it’s not common.
Instead, you use a domain name, like google.com or codinginterviewpro.com.
This is quite convenient because, for instance, I can change the location and hosting company for a website while keeping the same domain name.
The system responsible for matching domain names to IP addresses is known as DNS: Domain Name System.
The language computers use to communicate is called a protocol. The protocol behind the internet we all use is known as the Internet Protocol Suite, also called TCP/IP.
The IP protocol, as mentioned earlier, deals with IP addresses and forms the fundamental layer that helps computers locate each other.
Built on top of that layer, we have what we call transport protocols. They determine how computers send packets of data to one another.
One of these transport protocols is TCP, or Transmission Control Protocol. This protocol ensures that packets are successfully sent from the client to the server and vice versa.
Additionally, we have the UDP protocol, which is similar but has some differences. We’ll explore more about this later.
So, we now have the basics in place: devices, IP addresses, and the TCP/IP protocol, which ensures that data can smoothly flow between computers.
