What happens when you type google.com in your browser and press Enter?
Published: 2023-07-16 10:03:45

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

## **Introduction: How The Web Works**
In our daily lives, we often take for granted the seamless experience of browsing the web. The journey from typing "https://www.google.com" to seeing the search results is a fascinating interplay of various technologies and systems. In this blog post, we'll embark on an exploration of this journey, unraveling the intricate processes that take place, including DNS requests, TCP/IP connections, firewalls, HTTPS/SSL encryption, load-balancers, web servers, application servers, and databases. Get ready to delve into the hidden complexities that make the World Wide Web accessible at your fingertips.

## **1. DNS Request.**
* This is the first step in the journey. The browser sends a request to a DNS resolver. This could be the ISP's DNS server or a public DNS like the google DNS. The resolver's job is to translate the human-readable URL into a domain or an IP address, in this case, www.google.com (the domain) or 172.217.168.196 (google's Ip address).
* The DNS resolver follows a hierarchical process to resolve the IP address. It starts by checking its local cache to see if it has recently resolved the IP for the requested domain. If not found, the resolver contacts other DNS servers in a series of recursive queries until it obtains the IP address associated with the domain. This hierarchical system allows for efficient and distributed name resolution across the internet.
* Once the resolver receives the IP address for "www.google.com," it returns it to your browser. This IP address is essential as it acts as the destination for the subsequent steps in establishing a connection with the web server.

## **2. TCP/IP**
* After the DNS resolver returns the IP address of "www.google.com," the next step in the journey is establishing a connection using the Transmission Control Protocol/Internet Protocol (TCP/IP) suite. TCP/IP is a set of protocols that enables reliable and efficient communication over the internet.
- **TCP Handshake::** To initiate a TCP connection, your browser sends a SYN (synchronize) packet to the IP address obtained from the DNS resolver. This packet contains various details, including source and destination ports and sequence numbers.
- **Server Response::** Upon receiving the SYN packet, the server hosting "www.google.com" responds with a SYN-ACK (synchronize-acknowledgment) packet. This packet acknowledges the receipt of the SYN packet and includes the server's own sequence number.
- **Finalizing the Connection::** To establish a complete connection, your browser sends an ACK (acknowledgment) packet to the server. This packet confirms the receipt of the SYN-ACK packet, and the connection is now established.
- **Data Transfer::** With the TCP connection established, your browser and the server can now exchange data. Your browser sends an HTTP request to the server, specifying the resource (in this case, the homepage) it wants to retrieve.
- **Server Response and Data Transfer::** The server processes the request and generates an appropriate HTTP response. This response contains the requested web page's content, typically in HTML format. The server divides the response into packets and sends them back to your browser.
- **Reassembly and Rendering::** Once all the packets are successfully received, your browser reassembles them in the correct order. It then interprets the HTML content, fetches additional resources like images and scripts if necessary, and renders the web page on your screen.

>>> Throughout this process, TCP/IP ensures reliable data transmission by managing packet sequencing, flow control, and error recovery. It breaks the data into smaller packets and reassembles them at the receiving end, guaranteeing the integrity and order of the transmitted information. Understanding the workings of TCP/IP helps us appreciate the underlying mechanisms that enable smooth and efficient data transfer between your browser and the web server, making it possible to access websites like "www.google.com" with ease.

## **3. Firewall**
In the context of network security, a firewall acts as a barrier between your computer and the internet. It inspects incoming and outgoing traffic, applying rules to allow or deny specific network packets. Firewalls help protect against unauthorized access and potential threats.
Below are some of the functionalities of the firewall when filtering and controlling network traffic.
- **Filtering Network Traffic::** Firewalls work by analyzing incoming and outgoing network traffic based on a set of predefined rules. These rules define what is allowed or denied based on various criteria such as IP addresses, ports, protocols, and specific patterns within the network packets.
- **Packet Inspection::** When a packet arrives at your computer from the internet, it first encounters the firewall. The firewall inspects the packet and checks if it adheres to the defined rules. It evaluates the packet's source and destination IP addresses, ports, and other relevant information to determine whether it should be allowed through or blocked.
- **Traffic Control::** Firewalls provide granular control over network traffic. They can allow or block specific protocols, such as HTTP (web browsing), FTP (file transfer), or SMTP (email). Additionally, firewalls can restrict access to certain ports or IP addresses, preventing unauthorized connections to your system.
- **Application Awareness::** Modern firewalls often possess application-level awareness, known as next-generation firewalls (NGFW). These firewalls can identify and control specific applications or services traversing the network. For example, they can allow web browsing while blocking peer-to-peer file sharing or social media platforms, based on defined policies.
- **Configurable Security Policies::** Firewalls allow administrators to configure security policies based on the specific requirements of the network or organization. These policies can be tailored to permit or restrict certain types of traffic, set up virtual private networks (VPNs) for secure remote access, or create rules to enable specific services while protecting against potential vulnerabilities.

>>> They contribute to the overall security posture and help ensure a safer browsing experience when connecting to "https://www.google.com".

## **4. HTTPS/SSL**
When you type "https://www.google.com" in your browser, the "https" in the URL signifies that a secure connection is being established using the Hypertext Transfer Protocol Secure (HTTPS) protocol. This protocol adds an additional layer of security to protect the confidentiality and integrity of the data transmitted between your browser and the web server. Let's explore how HTTPS/SSL (Secure Sockets Layer) comes into play during this process:
- **SSL Handshake::** Upon initiating the connection to "www.google.com," your browser sends a request to the server, indicating its intent to establish a secure connection. The server responds by sending its digital certificate, which contains its public key and other identifying information.
- **Certificate Verification::** Your browser checks the server's digital certificate to ensure its authenticity and validity. It verifies the certificate's digital signature against trusted root certificates installed on your computer or maintained by your operating system or browser. This verification process confirms that the server is who it claims to be and that the certificate hasn't been tampered with.
- **Key Exchange::** Once the server's certificate is validated, your browser generates a unique session key, known as the symmetric key, to be used for encrypting and decrypting data during the session. It encrypts this session key using the server's public key obtained from the certificate and sends it back to the server.
- **Secure Connection Established::** The server receives the encrypted session key and decrypts it using its private key, which only the server possesses. Now both your browser and the server have the shared session key, which will be used for encrypting and decrypting the data transmitted between them.
- **Encrypted Data Transfer::** With the secure connection established, your browser and the server can now communicate securely. All data exchanged between them, including HTTP requests and responses, are encrypted using the session key. This encryption ensures that even if intercepted, the data remains unreadable and protected against eavesdropping or tampering.
- **Data Integrity::** HTTPS/SSL also ensures data integrity. When your browser receives data from the server, it calculates a cryptographic hash of the data and compares it with the hash provided by the server. If the hashes match, it confirms that the data hasn't been modified during transmission.

>>> By utilizing HTTPS/SSL, "https://www.google.com" ensures that the communication between your browser and Google's servers remains encrypted and secure. This encryption safeguards your sensitive information, such as login credentials, search queries, or any other data you transmit to the website. It gives you confidence that your interactions with the website are protected from unauthorized access.

## **5. Load Balancer**
In the case of popular websites like Google, load-balancers play a crucial role. A load-balancer distributes incoming requests across multiple servers, ensuring optimal resource utilization and high availability. It helps handle heavy traffic by evenly distributing the workload and redirecting requests to the least busy server. Here's how a load balancer works in the context of accessing Google's website:
- **Incoming Request::** When you press Enter after typing "https://www.google.com," your request reaches a load balancer. Load balancers are typically placed in front of a cluster of web servers to evenly distribute incoming traffic.
- **Traffic Distribution::** The load balancer intelligently routes the incoming requests across the available web servers. It uses various algorithms, such as round-robin, least connections, or weighted distribution, to determine how to distribute the load effectively.
- **Session Persistence::** In some cases, it is important to maintain session persistence, ensuring that subsequent requests from the same client are directed to the same server. This is commonly achieved by the load balancer inserting a session cookie in the client's browser, which is used to identify and route subsequent requests to the appropriate server.
- **Health Monitoring::** Load balancers continuously monitor the health of the web servers in the cluster. They regularly send health checks to ensure that the servers are responsive and functioning properly. If a server is found to be unresponsive or overloaded, the load balancer automatically takes it out of rotation, redistributing the traffic among the remaining healthy servers.
- **Scalability and Elasticity::** Load balancers facilitate horizontal scalability by allowing additional servers to be added to the server cluster as demand increases. This enables websites like Google to handle high traffic loads efficiently without compromising performance or availability. Load balancers can also provide elasticity by automatically scaling the server capacity up or down based on predefined rules or metrics.
- **SSL Termination::** In the case of HTTPS requests, load balancers can handle SSL termination. They decrypt the incoming SSL/TLS traffic, distributing the decrypted requests to the backend servers. This offloads the resource-intensive SSL decryption process from individual servers, improving overall performance and scalability.

>>> By utilizing load balancers, **Google** effectively distributes incoming traffic across multiple servers, ensuring optimal performance, high availability, and scalability. Load balancers play a crucial role in enhancing the user experience by efficiently managing the incoming requests and directing them to the appropriate servers in a balanced manner.

## **6. Web Server**
Once the request reaches the web server, it processes the request and fetches the requested webpage or resource. The web server can be software like Apache or Nginx, responsible for serving static files, processing dynamic content, and generating HTML pages. Web servers are responsible for processing incoming requests, fetching the requested resources, and generating appropriate responses. Let's explore how a web server works in the context of accessing Google's website:
- **Receiving the Request::** After passing through the load balancer, the request reaches one of Google's web servers. These servers are powerful machines equipped with specialized software, such as Apache or Nginx, designed to handle a large volume of web traffic.
- **Request Processing::** The web server receives the request and begins processing it. It analyzes the request headers, which include information such as the requested resource (e.g., the homepage), HTTP methods (e.g., GET, POST), and other metadata. The server identifies the appropriate action to take based on this information.
- **Fetching the Resource::** Once the web server determines the requested resource, it retrieves the necessary data or content. In the case of Google, it might fetch data from its vast index, perform complex search algorithms, or access other backend services to gather the information required to generate the response.
- **Dynamic Content Generation::** In addition to serving static files, many websites, including Google, generate dynamic content tailored to the specific request. The web server interacts with application servers or scripting languages, such as Python, Java, or PHP, to execute code that generates the dynamic content. This could involve performing calculations, accessing databases, or integrating with other services.
- **Response Generation::** Based on the retrieved data and dynamic content generation, the web server constructs the response. This typically involves generating an HTML page that contains the desired information, including search results, images, or other elements specific to the request.
- **Response Delivery::** Once the response is generated, the web server packages it into a network packet and sends it back to the client (your browser). The response includes an appropriate status code (e.g., 200 for successful requests), headers (e.g., content type, caching directives), and the content itself.
- **Handling Concurrent Requests::** Web servers are designed to handle multiple concurrent requests simultaneously. They employ techniques such as multithreading or asynchronous processing to ensure efficient utilization of system resources. This allows them to serve numerous users concurrently without significant delays or performance degradation.

## **7. Application Server**
In the case of complex web applications, an application server comes into play. It handles application-specific logic, such as executing code written in programming languages like Python, Java, or PHP. The application server interacts with databases, external APIs, and other resources required to generate dynamic content.
- **Request Processing::** After the web server receives the request, it may identify that the requested resource requires the execution of application-specific logic. In such cases, the web server interacts with the application server.
- **Application Logic Execution::** The application server is responsible for executing the code written in programming languages like Python, Java, or PHP. In the case of Google, the application server handles complex tasks such as search algorithms, personalized content generation, and data processing.
- **Communication with Backend Services::** To fulfill the request, the application server may need to interact with various backend services and APIs. For example, it might communicate with Google's indexing systems, retrieve data from databases, or integrate with other services to gather the necessary information to generate the response.
- **Business Logic Processing::** Application servers execute the business logic of the web application. This can involve performing calculations, applying algorithms, manipulating data, or enforcing specific rules and workflows defined by the application. In the case of Google, the application server processes search queries, analyzes user data, and generates personalized search results.
- **Response Generation::** Based on the application logic execution and interaction with backend services, the application server generates the final response. This response is typically in a format that the web server can understand and include in the overall response to the client (your browser).
- **Communication with web server::** Once the application server generates the response, it sends it back to the web server. The web server combines this response with any static content or additional resources it needs to deliver to the client.

>>> Application servers provide a crucial layer of functionality between the web server and backend services, handling the execution of complex application logic and processing dynamic content. They enable websites like Google to deliver customized, interactive, and dynamic experiences by executing code, integrating with various systems, and generating tailored responses based on the specific request.

## **8. Database**
Many websites rely on databases to store and retrieve data. When a request involves accessing or updating information stored in a database, the application servercommunicates with the database server. The database server manages the data, executing queries, and providing the necessary information to the application server, which then renders the appropriate response.
- **Request Processing and Application Server Interaction::** When the application server receives a request from the web server, it may need to access data stored in databases to fulfill the request. This data can include information about user preferences, search indexes, cached content, or any other relevant data required to generate the response.
- **Query Generation::** Based on the request and the specific data needed, the application server generates queries to retrieve the required information from the database. These queries are formulated in a database-specific language, such as SQL (Structured Query Language), to interact with the database management system (DBMS).
- **Database Interaction::** The application server communicates with the database server to execute the generated queries. The database server processes these queries, retrieves the requested data, and sends it back to the application server.
- **Data manipulation and processing::** Once the application server receives the data from the database, it may perform additional processing, manipulation, or aggregation based on the application logic and business rules. This processing can involve sorting, filtering, aggregating, or transforming the data to prepare it for presentation in the response.
- **Response Generation::** Using the retrieved and processed data, along with other components of the response, such as static content and dynamic content generated by the application server, the final response is generated. This response is then sent back to the web server for delivery to the client (your browser).
- **Data Persistence and Updates::** Databases also play a critical role in persisting and updating data for websites like Google. They store information related to user accounts, search history, indexing data, and other relevant data points. Databases ensure data consistency, integrity, and durability, allowing the website to handle massive amounts of data and provide reliable access to information.
- **Scalability and Performance::** Databases are designed to handle concurrent access and provide efficient data retrieval and storage mechanisms. They employ techniques such as indexing, caching, and query optimization to optimize performance and ensure that the website can scale to handle a large volume of requests.

>>> In summary, databases serve as the backbone of websites like Google, providing efficient data storage, retrieval, and management. They enable the application server to access and process the necessary data to generate dynamic content and fulfill user requests. By effectively managing data, databases contribute to the smooth functioning and performance of websites when you access them through your browser.