We use it on a daily basis, but do you know how the Internet works? What happens between entering the address of the website you want to visit and displaying it? How does the information pass between the Internet user and the requested resource? Let’s take a look at the whole subject to see how it works.
How the Internet Works – The Main Players
Before delving into the mechanics of the Internet, you need to have a good idea of the different players involved, and what their role is. There are others, but we will focus on the main ones.
ISP (Internet Service Provider)
It is with an ISP that you will be able to take out a subscription giving you the right to access the Internet.
FCA (Content and Application Provider)
FCAs are entities that have applications or content to pass through the Internet. This can be a company that offers a cloud service, or VOD for example.
DNS (Domain Name System)
The DNS will make it possible to translate a domain name (gafish.fr) into an IP address (18.104.22.168). To simplify this, we can compare it with a telephone directory, the domain name being the name and the IP the telephone number to dial to reach the recipient.
CDN (Content Delivery Network)
CDNs are servers that are geographically distributed and store cached copies of Internet content. They make it possible to speed up the distribution of content (a web page, an image, a film, software, etc.) because the idea is that they are geographically close to the end user. An example of use: you want to watch an episode of your favorite series, instead of fetching it from a server in the United States, it will be provided to you by a CDN located in France.
Autonomous System (AS, or autonomous system)
An autonomous system constitutes a basic building block of the network. It is a set of IP networks under the direction of an entity. This can be a corporate network with multiple sites but with a consistent internal routing policy. It can also be an ISP (see above).
Backbone (or Internet backbone)
These are the large strategic links which are the basis of the network and which have a large bandwidth. They make it possible to interconnect most of the Internet traffic, by linking together the Internet exchange points ( IPX ). This also includes inter-continental connections
How the internet works – Accessing the internet
To access the Internet as an individual, you must subscribe to an ISP (Internet Service Provider). In this context, he will provide you with a box which will be used to connect your home to his network infrastructure. This same box will also allow your local equipment (computers, telephones, tablets, connected TV, etc.) to connect to the local network (the box will provide them with a local IP address), and also to be able to access the Internet via the box.
Once connected to your access provider, you will already have access to the latter’s CDN, because in general there are often CDNs at ISPs. This ISP is also an Autonomous System (AS). As an AS, he will be able to discuss with the ASes close to him, and thus gradually arrive at the requested resource.
This step-by-step communication is done via BGP routes . The information then passes through peering agreements (agreement between two parties), or in transit (purchase of a transit right on a network).
How the internet works – Accessing web content
Already, we must not confuse internet and web. Internet is the network supporting many uses and applications, including the World Wide Web (WWW).
When you seek to access a web page, you will therefore use the Internet network to access web content.
To access a page, you enter its URL (address) which includes, among other things, its domain name. Broadly, the steps will be as follows to return the content to you:
- Using DNS to match this domain name with an IP address. This IP address will be that of the destination server.
- Contact the destination server with the url and send parameters to it. Among the information that is sent to the server, there is already the url that will allow it to know what content you want. But you also send a lot of other information via HTTP headers. In these headers, you will have, for example, session information that will allow the server to know who you are if the page you wish to consult is subject to a connection (for example a shopping cart on an e-commerce site). If you want to know the list of headers, you can check this documentation on HTTP headers at Mozilla .
- The web server (this can be an Apache, IIS, Nginx server, etc.) analyzes and processes this information. Depending on the rules that have been implemented on the server, it prepares the response (which will be the content of a web page, for example).
- This content is sent to the recipient, namely the web user’s browser. The page is then displayed on the latter.
This information travels on the network in the form of network packets .
How the Internet Works – Net Neutrality
We saw in the previous paragraph how information travels in packets from the point of departure to its destination. Net neutrality is a principle that allows each packet of information, regardless of its sender or recipient, to be treated identically. This is a very important principle, because it guarantees a free flow of information. It is a source of tension between ISP and FCA, in particular due to the increasing volumes circulating on the network, in particular due to large content providers.
In Europe, this principle is applied. He hasn’t been in the United States since 2018.
On the occasion of the debate which took place on the subject in the United States, a program by John Oliver dealt with the subject. If you speak English, I recommend it (add English subtitles if necessary), it will allow you to better understand the subject with humor.
To go deeper
Here are some videos on the subject, to illustrate, or in addition if you want to go further.
A video explanation of how the network works:
Going further on pearing and transit:
An introduction to BGP routes: