Lesson 1:
What is the internet?
The Internet is a huge network of computers and other electronic devices around the world that are connected to each other and therefore can share information. As we’ll see later, that connection can be:
- Wired: that is, using an electrical cable or an optic fiber cable.
*A group of several wires that are isolated one from each other is called a cable.
- Wireless: using electromagnetic waves that travel through the air.
The origin of the Internet dates back to 1969, when four universities in the United States began to connect some of their computers in a network that they called the ARPANET. At that time the applications of that network were purely military. However, as time went by, more and more computers were connected: 24 in 1971, 2013 in 1981, 500 in 1983 … This quick growth caused the exchange of information spread to many other applications (not related to security and the army), giving rise to the Internet as we know it today.
However, we are going to see how the structure of the Internet is not as simple as it might seem. Computers around the world are not connected to each other in any way and getting information to travel from one to another in an efficient way and safely is not easy at all.
Internet providers.
ISP (Internet Service Provider) are the companies that allow us to connect to the internet, either with a computer, mobile phone or any other device. In other words, they allow us to convert an isolated device into a device that is connected to the great international network that is the Internet. The most important internet providers in Spain are:
How to connect to the internet.
Every day we enter web pages and other internet services such as email with multiple devices (mobile phones, tablets, laptops …). But, how is this connection made? Where is all the information on the internet stored? Why does a web page sometimes stop working?
What is a router?
A router (from the word «route») is the device through which electronic devices (of a home, an office, a school …) connect to the internet. To connect a device to a router it is necessary to know its password and therefore only people who have this password will be able to connect their devices to the internet using that router (there are some exceptions in public places whose routers do not require a password).
The set of devices, physically close to each other, and that are connected to the same router (although they can also be connected to another device called a switch without the need for internet access) is called a local area network, better known by its acronym LAN. This connection can be made by cables like the one in the image below:
Or wirelessly, in which case the network is called WLAN (Wireless Local Area Network). To be able to connect a device wirelessly to a router, it must have antennas that transmit the information using electromagnetic waves (Wi-Fi).
Therefore, you may have several computers, mobile phones, printers, televisions connected to each other at home… What’s more, as shown in the image below, some components can be connected to the router by cable while others are wirelessly connected:
Electrical cable or optic fiber?
As we’ve explained before, the connection point between the internet and a local area network is the router. In other words, the router of a network is like a gateway to the Internet, therefore, all the information that enters or leaves a LAN goes through it. The connection between the router and the rest of the internet can be done in two different ways:
- Using an electrical cable made of several copper wires. This is the case when the Internet reaches a home through an ADSL line.
- Through optic fiber cables, made of glass. In this case, the information arrives in the form of pulses of light. This method allows for much higher information transmission rates and greater reliability in communication since the interference is much lower.
There is a third way in which information can get to the router, which is by electromagnetic waves from a satellite. However, this method is very expensive and is only used in geographically isolated areas that cannot be reached by other means.
Public and private IP adresses.
Each router on the Internet is identified with a numeric code made of four numbers from 0 to 255 separated by dots. That code is called IP address. An example could be:
173.194.41.229
The IP address is like the address of a house since it allows us to identify a router in order to send it some information. The IP address of a router is unique and there can’t be another router with the same address (just like the address of a home must be unique so that the letters reach the mailbox properly). Otherwise, information that is being sent to a particular person through the internet could reach the wrong person.
All devices that are connected to the same router have the IP address of that router. If you want to check the IP address of a device (that is, the IP address of the router to which you are connected) you can do it here: https://whatismyipaddress.com/. You can check how if both your phone and laptop are connected to the same wifi network their IP address will be the same. This address is assigned by the internet provider and therefore we cannot choose it.
The IP address that we have studied is actually called the public IP address since it is the address of a router (and the devices connected to it) in the whole internet. However, in order to distinguish among the different devices that are connected to the same router, it assigns them another code, the so-called private IP address. This way, when information reaches our home router, it only forwards it to the device that requested it. For example, if a Wikipedia search has been made on one of the home computers, the result will only be displayed on that computer, not on all the connected devices.
To know the private IP adress of a device you need to follow these steps (in Windows):
- Open the command prompt by typing cmd in the search box.
- Then write «ipconfig» and press enter.
- Your private IP address is the code that appears as IPv4 Address.
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