What happens when you type "google.com" in your browser and press Enter

Have you ever wondered what goes on behind the scenes when you enter a URL in your browser and navigate to your favorite websites? How does the webpage magically appear when you press enter after typing in the URL? And how are the images and content displayed on the page? It may seem like a simple and quick process, but in reality, loading a website involves a complex infrastructure.

In this blog post, we will take an in-depth look at the technical process of loading a website, covering everything from the initial DNS request to the final display of the web page. This end-to-end journey involves multiple components, including your browser, your computer's operating system, your internet service provider, the server hosting the website, and the services operating on that server. Let's unravel the mystery behind the seamless experience of browsing the internet and explore the intricate workings that bring your favorite websites to your screen.

DNS Request:

When you type "google.com" in your browser's address bar and press enter, it initiates a series of events known as DNS (Domain Name System) resolution. This process involves converting the human-readable domain name, such as "google.com," into a computer-friendly IP address (like 192.168.1.1), which informs your browser which server to communicate with.

Every device connected to the Internet, including servers, cell phones, and even smart refrigerators, has a unique address called an IP address. This address is essential for locating the specific Internet device, similar to how a street address is used to find a particular home.

Think of DNS as the Contacts app on our phones. It acts as a directory that helps our browser (and us) locate the IP addresses of servers on the Internet based on the domain name, such as "google.com." This seamless translation enables us to access websites and services with ease.

DNS Lookup Process: Understanding the Steps and Involved DNS Servers

Note: DNS lookup information is often cached either locally inside the querying computer or remotely in the DNS infrastructure, which can skip steps in the DNS lookup process and make it quicker. However, when nothing is cached, there are typically 9 steps in a DNS lookup. The example below outlines all 9 steps.

1. User Input: A user enters 'google.com' into a web browser, and the query travels into the Internet and is received by a DNS recursive resolver. This resolver is usually provided by our Internet Service Provider (ISP).
2. Query to Root Nameserver: If the resolver doesn't find the IP in its cache, it queries a DNS root nameserver.
3. Response from Root Server: The root server responds to the resolver with the address of a Top-Level Domain (TLD) server that stores information for its respective domains. In this case, the TLD is '.com', while other examples include '.net', '.fr', and so on.
4. Query to TLD Server: The resolver then makes a request to the '.com' TLD server.
5. Response from TLD Server: The TLD server responds with the IP address of the domain's authoritative name server, "google.com". Usually, there is more than one name server attached to a single domain name.
6. Query to Authoritative Name Server: The resolver sends a query to the domain's authoritative name server.
7. Response from Authoritative Name Server: The IP address for "google.com" is returned to the resolver from the authoritative name server.
8. DNS Resolver Response: The DNS resolver then responds to the web browser with the IP address of the initially requested domain.
9. HTTP Request and Response: An HTTP request is made by the browser to the IP address, and in response, the server at that IP address returns the webpage to be rendered in the browser.

Additional notes:

• Additional requests may be necessary to locate the correct IP address if the DNS record is not found at any of the name servers or if the record has been configured to use services like DNS load balancing or content delivery networks (CDN).
• Once the IP address has been successfully resolved, it is cached by the local DNS resolver and the browser to improve the speed of future requests to the same domain name.
• The length of time that the DNS record is cached, known as the "Time To Live" (TTL), is determined by the authoritative nameserver and can be adjusted by the domain owner to balance the need for fast response times.

TCP/IP:

After the browser obtains the DNS record with the IP address, the next step is to locate the server on the Internet and establish a connection.

The TCP/IP (Transmission Control Protocol/Internet Protocol) is the common protocol used for various types of HTTP requests. It functions as a set of rules governing the format of data transmitted over the internet or local network, enabling activities such as sending emails, streaming videos, or connecting to a website.

The TCP/IP model enhances the integrity of each communication by breaking down data into smaller packets and then reassembling them into the complete message on the receiving end. This approach of sending data in manageable packets enhances accuracy compared to transmitting all the data at once.

Some of the common protocols that work in conjunction with the TCP/IP model include HTTP, FTP, and SMTP. These protocols play vital roles in facilitating web browsing, file transfers, and email communication, respectively. By using the TCP/IP model in conjunction with various protocols, the internet achieves seamless and reliable data transmission, enriching our online experiences.In a nutshell, IP is responsible for locating the proper path for delivering packets. TCP is responsible for end-to-end delivery and the correction of errors on that path.

Traffic and security control.

With the TCP connection established, the data transfer can begin! But before we proceed, we need some traffic control – introducing the load balancer...

A Load Balancer plays a vital role in evenly distributing incoming traffic across multiple servers, ensuring that no single server is overloaded. This intelligent distribution not only enhances website performance but also prevents server crashes, resulting in a more reliable browsing experience.

For high-traffic websites like "google.com," load balancing becomes crucial to maintain optimal performance and handle the enormous number of requests effectively. When a user's request arrives, the load balancer assigns it to a specific server, repeating this process for every subsequent request. Various algorithms guide load balancers in determining which server should handle each incoming request.

Now, while the load balancer efficiently manages the incoming traffic, let's ensure the network remains secure with the assistance of a firewall.

A firewall serves as a network security system, actively filtering incoming and outgoing network traffic based on pre-defined rules. It acts as a protective barrier against unauthorized access, shielding the servers from potential threats such as hackers and malware.

When you type a URL like "google.com" in your browser, the request passes through a firewall, which carefully inspects the incoming traffic to ensure it adheres to the established security rules. These rules can include restrictions on the requesting IP address, the frequency and number of requests, or even the type of content being sought. Additionally, some browsers come equipped with built-in firewalls that can detect potential malicious agents based on the IP obtained from the DNS request.

HTTPS/SSL: Emphasizing Secure Connections

Having obtained the IP address, the browser now shifts its focus to the other part of the URL, the "https://" part

HTTPS, which stands for HyperText Transfer Protocol Secure, is an upgraded and secure version of the standard HTTP. It plays a critical role in safeguarding sensitive data exchanged between a web server and a user's browser, making it difficult for attackers to intercept and steal information like login credentials and payment details.

SSL, or Secure Sockets Layer (also known as TLS, Transport Layer Security), is a set of encryption protocols used to secure the data transmitted over HTTPS. This protocol ensures secure communications through an asymmetric public key infrastructure. Such a security system relies on two distinct keys for encrypting communications:

1. Private Key: Controlled by the website owner, the private key resides on the web server and is used to decrypt information that was previously encrypted by the public key.
2. Public Key: The public key is available for secure interactions with the server and can be accessed by anyone. Data encrypted with the public key can only be decrypted using the corresponding private key.

We can easily identify if a website is using HTTPS/SSL by looking for a little lock icon next to the website name in the search bar. Together, HTTPS and SSL create a secure communication channel, ensuring that data exchanged between a client and a server remains protected.

When you enter "google.com" into your browser and press enter, if the website uses HTTPS/SSL, the browser initiates a secure connection with the server through the SSL/TLS handshake process. This involves verifying the server's SSL/TLS certificate, generating an asymmetric encryption key, and subsequently encrypting all data transmitted between the browser and server. Once the handshake is complete, the browser sends an HTTPS request to the server to fetch the web page content, and the server responds with an HTTPS response, providing the necessary resources for rendering the web page in the browser.

Without HTTPS and SSL, websites would be far more susceptible to attacks, and sensitive information would be at a higher risk of being compromised. Therefore, the implementation of HTTPS and SSL has become crucial for ensuring the security and privacy of online communications.

web and application servers:

Once the secure connection is established and the user's request is received, the web server takes charge of serving up the requested web page.

A web server is a combination of software and hardware that uses HTTP/S and other protocols to respond to clients' requests and deliver static content, such as HTML, images, plain text files, CSS, and JavaScript files (also known as static files) that are essential for rendering the web page in the user's browser. Popular web servers like Apache and Nginx are widely used today for their reliability and performance.

The web server serves as the foundation of any web page, ensuring that static content is delivered efficiently and accurately to the user. However, most websites are not just static pages; they are dynamic and interactive. This means that users can interact with the site, save information, log in with a username and password, and perform various actions.

For dynamic websites and applications, an application server comes into play. The application server is a software program responsible for handling the operation of applications, managing user information, communicating with database servers, and more. It works in conjunction with web servers and utilizes the static content served by the web server to deliver dynamic content and functionality to users. This enables users to interact with the site in real-time and perform actions that modify the content based on their inputs.

Application servers play a crucial role in ensuring that dynamic applications run smoothly and efficiently. They work behind the scenes to process user requests, interact with databases to fetch or update data, and deliver the appropriate response to the web server, which, in turn, delivers it to the user's browser.

Some of the most commonly used application servers today include Tomcat and JBoss, both renowned for their robustness and ability to handle complex applications effectively.

Database: Storing and Retrieving data.

The last step in our web infrastructure is the Data Base Management System (DBMS). A database is a structured collection of information, organized in a way that enables easy management and retrieval. It serves as a central repository for various types of data, such as customer information, product catalogs, financial records, and more. The data stored in a database can be accessed, modified, and analyzed with the help of a database management system (DBMS). This system provides a set of tools and functionalities that ensure data integrity, security, and efficient querying

There are several types of database models, each tailored to specific data requirements and use cases. The two main categories are relational databases and non-relational databases.

Relational databases, such as PostgreSQL, MySQL, SQLite, and MariaDB, are based on the relational model, which organizes data into tables with rows and columns. This model enables the establishment of relationships between tables through primary keys and foreign keys, facilitating complex data retrieval and manipulation.

On the other hand, non-relational databases, also known as NoSQL databases, use various data models to store and manage data. Examples of NoSQL databases include MongoDB, Cassandra, and Redis. These databases are suitable for handling large volumes of unstructured or semi-structured data, making them ideal for applications that require flexible and scalable data storage.

Database management systems play a vital role in ensuring data integrity and security. They provide mechanisms for data backup, recovery, and replication, protecting valuable information from data loss or corruption. Additionally, DBMSs implement access control mechanisms, allowing administrators to define user privileges and restrict unauthorized access to sensitive data.

With the combination of web servers, application servers, and a reliable database management system, the seamless flow of data and content from the server to the user's browser is achieved. As a user interacts with a website or application, the data is processed and retrieved from the database, delivering dynamic and personalized content.

conclusion

The process of loading a webpage involves a complex web infrastructure that seamlessly connects your browser to the server hosting the website. From the initial DNS resolution to the secure HTTPS/SSL handshake, traffic control with load balancers, and data retrieval from databases, each step contributes to delivering a fast, secure, and interactive browsing experience. Understanding this technical process enhances our appreciation for the intricate mechanisms that power the internet, ensuring that we can effortlessly access our favorite websites and applications with just a simple click.