What Happens When You Type Google.com in Your Browser?

Have you ever wondered what happens behind the scenes when you type Google.com (or any other domain) in your browser?

Well in this article, I will be breaking down this fascinating process as part of my ALX software engineering assignment.

Let's dive in!

When you type Google.com in your browser, you are literally asking your device for the default page of google from google servers, which you can think of as a computer or group of computers that host all google information and serve them to anyone that asks for it.

Although this process generally takes a few seconds, there is a lot that happens behind the scenes. It begins with finding the address of the google server, sending the request to the server to finally receiving the response from the server.

1- Finding the IP address:

When you type google.com in a browser, in order to for the client device to know exactly which server is associated with google.com, it needs the IP address of google.com. An IP address is a unique identifier of a computer (both client and server) over the internet.

Since IP addresses are generally a series of numbers that are difficult to recall by the average human being, like 8.8.8.8 and 8.8.4.4 for Google IPv4 addresses, the need for a system called Domain Name System or DNS which translates all IP addresses to easily recallable domain names like "google.com" came about.

The translation of a domain name to an IP address goes through several processes which are as follows:

• Your device first checks the cache of your browser which generally will store recently used domain names. If the IP address is found in the cache, it begins the next phase of sending the request the the google server.
• If not found in the browser cache, your device's host file which is a file on your computer that stores useful IP addresses is checked. If found, your browser begins the next step of sending the request to the browser. (QUICK NOTE: In the beginnings of the internet, the host files were the main lookup systems used to translate domain names into IP addresses but with the coming as the internet grew, so did the need for space to store all the IP addresses on the internet on every computer. Another limitation of the host files was the fact that developers had to update these files each time a new domain came about. However, a common use of the host file is to change the IP address a domain name points to. For example you could make google.com to point to google.com/example/of/path. This is possible because the device first searches for the domain in the host files before searching in the DNS).
• If the IP address is still not found, a DNS request is sent to the DNS resolver using the Transfer Control Protocol or TCP protocol which provides reliable, ordered, and error-checked delivery of a stream of data between applications running on hosts communicating via an IP network. The DNS resolver is a server often provided by the Internet Service Provider (ISP) , which is configured specifically to find IP addresses. The DNS resolver first searches its cache for the IP address and then sends the request to the Root DNS Server which generally doesn't know the IP address but knows which Top Level Domain or TLD server (like .com) is responsible for the domain. The TLD server then points the resolver to the Authoritative DNS server for the specific domain which, holds the records of IP addresses for that domain. The resolver retrieves the IP address from the Authoritative DNS server, caches it for subsequent requests and finally sends the IP address back to your browser allowing it to connect to the desired website.

2- Sending the Request to the Server

After obtaining the IP address, your browser needs to establish a secure connection using HTTPS, which employs SSL (Secure Sockets Layer) encryption. This ensures that the data transferred between your browser and Google's servers is secure.

Once the connection is established, your browser sends an HTTP request to the web server at the resolved IP address. This request includes:

• A request line starting with "GET" for the default page.
• A list of headers, identifying the host as www.google.com and providing additional information.

USEFUL INFORMATION:

• Since Google handles millions of requests simultaneously, it uses load balancers to distribute incoming traffic across multiple web servers. This ensures no single server is overwhelmed and helps optimize response times.
• Once the appropriate web server receives the request, it processes it and may pass it to an application server if needed. The application server handles the logic to generate the appropriate response, which might involve querying a database to retrieve information.

2- Serving the response:

The web server then sends back a response composed of:

• A status code (like 200 OK if successful)
• A list of response headers, including the content length which tells the browser about the amount of data it should expect in the response.
• The body, containing the HTML content to be displayed in your browser

If the HTML references additional resources like CSS or JavaScript files, the browser will send separate requests for those.

USEFUL INFORMATION:

Your request must pass through any firewalls configured on the server. Firewalls control incoming and outgoing network traffic, blocking unauthorized IP addresses and types of requests to protect the server from attacks.

In summary, accessing a website involves a complex series of steps and coordination among various components. I hope you enjoyed learning about this as much as I did. I will be very grateful to see your comments, contributions and corrections in the comment section