Have you ever wondered what happens when you pick up your phone or computer, open your browser — be it Chrome, Firefox, Safari, or another — and type in “https://www.google.com"? It seems almost magical: you press “Enter,” and the Google homepage appears almost instantly. But hold up — while we're busy thinking it's instant internet magic, a lot is happening behind the scenes. It's like expecting a pizza to appear in your hands after you hit 'order now' — if only it were that simple, right?

Imagine a team of busy little robots running around, finding IP addresses, making secure connections, and moving data super fast, all to make sure you can instantly look up why dogs tilt their heads. Sounds interesting? This write-up will break down the fascinating series of events that take place to make this possible, including DNS resolution, establishing a secure connection, HTTP requests, the role of load balancers, firewalls, web servers, application servers, databases, and finally, rendering and displaying the page. Well, buckle up, because we're about to dive into how it all works below!

The process of DNS resolution involves converting a domain name or hostname (such as google.com) into an IP address (such as 8.8.8.8). It converts a human-readable domain name into its corresponding IP address so that your browser can locate and access the website.

When you type “https://www.google.com" into your browser , the first thing your browser does is check its cache to see if it already knows the IP address for Google. You might be wondering, what a cache and an IP address are. Well, a cache is like your browser's little notepad where it jots down addresses it's visited recently so that it can find them faster next time. Every device on the Internet has its unique IP address, which is essential for locating that device — just like a room number helps you find a specific room in a large hotel. As mentioned earlier, a common example of an IP address is 8.8.8.8. This particular IP address belongs to Google's public DNS service.

Unluckily, if your browser does not know the IP address for Google it needs to find out the IP address, which is where DNS (Domain Name System) comes in. Think of DNS as the internet's phonebook. Your browser sends a request to a DNS server to find out what IP address corresponds to “google.com”. This request can travel through several DNS servers, each passing it along until the correct IP address is found. Once your browser gets the address, it knows where to send your request next.

Once the IP address is known, your browser initiates a TCP (Transmission Control Protocol) connection to Google's web server at that IP address.

TCP ensures reliable communication by managing the connection setup, data transfer, acknowledgment, and termination processes. Imagine a phone call between two people who want to have a conversation. In TCP, this is like the process of setting up a connection. Your computer makes sure the other computer, which hosts Google's server, is available and ready to talk before starting the conversation. This involves a three-way handshake process:

1. SYN: Your browser sends a synchronized packet to Google's server to start the connection

2. SYN-ACK: The server then responds with a synchronize-acknowledgment packet.

3. ACK: Your browser sends an acknowledgment packet back to the server.

After a successful connection, data is transferred in segments. When you type https://www.google.com in your browser and hit enter, your request is broken down into smaller data segments. Each segment includes a sequence number that helps in reordering the segments at the destination if they arrive out of order. TCP uses a mechanism called windowing to control the flow of data. It ensures that the sender does not overwhelm the receiver by sending more data than it can handle. Each segment also includes a checksum to detect errors in the data. If a segment is corrupted, it is retransmitted.

Further, for each data segment received, the receiving computer (in our case, Google's server) sends an ACK back to the sender. This acknowledgment indicates that the segment was received correctly. If the sender does not receive an acknowledgment within a certain time, it will retransmit the segment. TCP uses retransmission timers to detect and recover lost packets by sending them again.

So, the data sent in segments includes the requests we make when typing a URL like https://www.google.com. TCP ensures that these requests are delivered reliably and in the correct order, making sure that we get the web pages we want to access smoothly and efficiently. The connection remains open until the page has been fully rendered.

Since you are accessing the site via HTTPS (a secured version of HTTP), a TLS (Transport Layer Security) handshake occurs to establish a secure connection. TLS is an encryption and authentication protocol designed to secure Internet communications. This involves exchanging cryptographic keys and verifying the server's certificate (usually signed by a trusted Certificate Authority such as Let's Encrypt, GoDaddy, Entrust and many more). SSL, or Secure Sockets Layer, was the original security protocol developed for HTTP. It has since been superseded by TLS, or Transport Layer Security. Nowadays, the process formerly referred to as SSL handshakes is called TLS handshakes, although the term “SSL” remains widely used.

TLS 1.3, the latest version of the Transport Layer Security protocol, brings a major speed boost with its handshake process. Unlike earlier versions that required multiple exchanges between the client and server — known as round trips — TLS 1.3 can complete the handshake with zero round trips. This means that the secure connection is established almost instantly, speeding up the process and improving security.

Here's a simple bonus: If you've visited the Google website before, the client and server can use a special shared key from the first visit, called the “resumption main secret.” During that first visit, the server gives the client a session ticket. When you return to the website, your browser can use this key and ticket to quickly set up the secure connection again without starting from scratch. This makes reconnecting faster and more seamless.

After your browser resolves the IP address through DNS and establishes a secure connection using TLS, it's time for the next step: making an HTTP GET request. Your browser sends an HTTP GET request to the server which includes the request lines (HTTP method, the path to the resource, etc.) the request headers that provide information about the client (browser type, language, etc.), and the request body (optional section here as it is mainly used in POST requests to send data to the server, such as form submissions).

Here's what an HTTP GET request might look like:

Before your request reaches Google's web server, it first passes through a firewall. It's important to dwell on firewall because it plays a crucial role in ensuring the security of web interactions. Think of the firewall as a security checkpoint. Its job is to screen incoming requests to make sure they are safe and legitimate.

Imagine you're trying to enter a secure building. The security guard checks your ID and questions why you're there. If everything looks good, you're allowed inside. Similarly, the firewall inspects each request for signs of malicious activity or unauthorized access attempts.

For example, if someone tries to send harmful code or exploit vulnerabilities, the firewall blocks those requests. Only the safe and authorized requests make it through to Google's web server. This helps protect Google's servers from potential threats and ensures that your visit to https://www.google.com is secure.

Once the secure connection is established, finally, your request reaches Google's load balancer. It's also important to talk about this step because load balancers play a crucial role in managing internet traffic. They act like traffic directors, distributing incoming requests across multiple servers to ensure no single server becomes overwhelmed. This helps improve resource use, reduce delays, and increase reliability. The load balancer decides which server will handle your request based on factors like how busy each server is, the health of each server, and where the server is located geographically. After considering all these factors, it then sends your request to one of Google's web servers.

Once the load balancer has directed your request to a specific server, the server begins processing it to determine what content to send back, in this case, the Google homepage. The server retrieves the necessary data to display Google's homepage. This includes fetching the HTML, images, and other static resources that make up the main page.

After the request passes through the firewall and reaches Google's web server, it is handed off to the application server. The application server is crucial for managing more complex tasks beyond serving static files and resources. It plays a key role in turning the static resources provided by the web server into a fully functional and customized webpage. Here's a breakdown of its role:

1. Running Dynamic Code: The application server executes scripts and programs that generate dynamic content. For example, when you visit https://www.google.com, the application server might run code to customize the homepage based on your location or preferences, even though you're not performing a search.

2. Handling Business Logic: It processes the business logic required to build the web page. For instance, the application server manages how different elements on the homepage are arranged and ensures that interactive features, like language settings or theme preferences, work correctly.

3. Managing Sessions: If you have an active session or cookies from previous visits, the application server checks these to provide a personalized experience. It might adjust what you see on the homepage based on your past interactions with Google.

4. Communicating with the Database: Although the homepage might not need extensive data from the database, the application server is responsible for fetching or updating information as needed. For example, if the homepage includes personalized content, the application server might retrieve relevant data from Google's database.

5. Preparing the Response: After processing the request and running the necessary code, the application server collaborates with the webserver to prepare the HTTP response. This response includes the final content to be sent back to your browser.

Database plays a crucial yet often behind-the-scenes role when you visit Google's homepage. In essence, it holds a wealth of information necessary for various features and services. This might include storing user preferences, session information, and any data relevant to personalization. Although you're just visiting the homepage, the database can provide personalized content if you have cookies or a logged-in session.

For instance, if Google tailors its homepage based on your location or language preferences, the application server queries the database to fetch and display this information. Moreover, if you've interacted with Google services before, the database keeps track of your settings and preferences, so when you visit the homepage, the application server might retrieve this data to ensure a consistent and personalized experience.

After processing the request and running the necessary code, the application server collaborates with the webserver to prepare the HTTP response, which includes:

1. Status Code: A number indicating the result of your request (e.g., 200 OK for success, 404 NOT FOUND if the page doesn't exist).

2. Headers: Information about the response, such as:

• Content-Type: The type of content being sent (e.g., HTML, JSON).

• Content-Length: The size of the content.

• Set-Cookie: Instructions for your browser to store cookies.

3. Body: The actual content you requested (the HTML of Google's homepage).

Once your browser receives the HTTP response from Google's servers, it begins the process of rendering and displaying the Google homepage. The browser starts by parsing the HTML content from Google's server. This HTML includes the structure of the Google homepage, such as the search box, Google logo, and buttons. The browser constructs the Document Object Model (DOM), a tree-like structure representing these elements. Each HTML element, like the search bar and buttons, becomes a node in the DOM, providing a framework for the browser to understand and manipulate the content.

As the browser parses the HTML, it identifies links to additional resources such as CSS stylesheets, JavaScript files, and images. For the Google homepage, this might include styles for the search box and images for the Google logo. The browser sends requests to fetch these resources, ensuring that the complete set of components needed to display the page is available.

The browser then parses the CSS files it retrieved to build the CSS Object Model (CSSOM). The CSSOM defines how the elements in the DOM should be styled. For example, it will include styles for the search box's appearance, the alignment of the Google logo, and the layout of buttons. This model works with the DOM to apply these styles correctly.

Combining the DOM and CSSOM, the browser creates the render tree. This tree includes all visible elements, like the Google search bar and logo, and their corresponding styles. Elements that are not visible, such as hidden ads or elements with display: none, are excluded from this tree.

The browser calculates the size and position of each element on the render tree, a step known as layout or reflow. For Google's homepage, this means determining where the search box, logo, and buttons will appear on the screen. Further, it arranges these elements based on factors like the size of the viewport and the dimensions of other elements.

With the layout complete, the browser starts painting. This step involves rendering the visual aspects of the page, such as applying colors, borders, and backgrounds. For Google's homepage, the browser paints the search bar in its designated color, displays the Google logo, and styles the buttons as specified.

If there are JavaScript files or inline scripts on the homepage, the browser executes them. For example, JavaScript might manage interactive features like the search button's functionality or handle user interactions. This script can also make the page more dynamic by updating content or reacting to user actions.

Once the rendering process is complete, the browser displays the fully constructed and styled webpage. You see the fully styled and functional page, including the search bar, Google logo, and buttons. The page appears as intended, with all elements in their proper places and ready for use.

TCP termination typically occurs after the web page has been fully rendered, as mentioned above. Once the browser has received all necessary data segments to complete the web page, the connection is closed using a four-way handshake process:

1. FIN: The client's computer sends a FIN (finish) packet to indicate that it has finished sending data.

2. ACK: The server responds with an ACK to confirm it received the FIN packet.

3. FIN: The server then sends its own FIN packet to indicate it has finished sending data.

4. ACK: The client responds with an ACK to confirm it received the server’s FIN packet. After this, the connection is fully closed.

As you interact with the homepage, such as typing a query into the search box or clicking the “Google Search” button, the browser may send additional requests to Google's servers. These interactions can trigger new HTTP requests to process your search query or navigate to other pages, continuing the dynamic nature of the browsing experience.

Google's homepage may include features that update in response to your actions, such as dynamic search suggestions or updates to the page layout. The browser handles these updates smoothly, ensuring that the page remains responsive and engaging throughout your interaction.

In sum, when you visit https://www.google.com, a complex sequence of technological processes works behind the scenes to display Google's homepage on your device. Initially, your browser translates the domain name into an IP address through DNS resolution. It then establishes a secure connection with Google's servers using TLS. Once the secure connection is set up, your browser sends an HTTP request to Google's servers. This request is handled by a load balancer that distributes incoming traffic across multiple servers, optimizing performance and reliability.

The web server processes the request, possibly interacting with an application server and a database to retrieve or manage data needed to generate the homepage. A firewall plays a crucial role throughout this process by protecting the servers from unauthorized access and potential threats, ensuring that only legitimate requests are processed. After the request is processed, your browser begins rendering the page. This involves parsing the HTML, fetching additional resources, and building the visual representation of the page. Finally, the fully rendered Google homepage is displayed on your screen, allowing you to interact with it. This entire process, from initial request to final display, involves multiple layers of technology and security measures that work together to provide a seamless and secure browsing experience.

Thank you for taking the time to read this article and explore the fascinating journey that happens behind the scenes when you visit Google's homepage. I hope this insight into web technology has been both informative and engaging!

Written by Yusuf Mustapha Opeyemi. July 22, 2024.

• What is DNS — Cloudflare

• What is TCP/IP in Networking?

• What happens when you type www.google.com and press enter - FreeCodeCamp

• The sequence of actions and network communication involved in accessing Google's homepage — ChatGPT

• Client Server Network — Study.com