How the web works: What happens when you type https://www.google.com in your browser and press Enter.

Today, the web is everywhere, from ordering things online to connecting with friends and families via instant messaging. Life is unimaginable without the web in today’s world, it plays a crucial role in the development of the world.

When you type in your favourite web address (like https://www.google.com) into your web browsers (like Firefox, Google Chrome, Safari etc), within a fraction of seconds the web page you desire to view quickly pops up on your screen. However, several background activities happen behind the scenes before those beautiful web pages get to be displayed in your browser.

In this article we will be discussing these behind the scenes activities to help us understand what happens when we type a web address in our browser and press enter.

Put simply, when you type a web address like "https://www.google.com" into your browser and press Enter, your browser starts a process to visit Google's website. First, it checks with a special directory called the Domain Name System (DNS) to find out the exact address of the server where Google's website is stored. Once it gets this information, your browser establishes a connection with that server over the internet. Then, it asks the server for the Google homepage. The server sends back all the necessary files and data to display the homepage properly. Your browser then takes these files and interprets them, turning them into the familiar Google search page that you see. Finally, it displays this page on your screen, allowing you to search the internet using Google's search engine.

Let’s look at the following concepts that make up this whole process:

• DNS request
• TCP/IP
• Firewall
• HTTPS/SSL
• Load-balancer
• Web server
• Application server
• Database

1.?? DNS request: Think of DNS (Domain Name System) as the internet's phonebook. When you want to visit a website, you type in the domain name (like www.google.com). However, computers communicate through IP (Internet Protocol) addresses, which are like unique phone numbers. DNS translates the human-readable domain names into IP addresses, so your browser knows where to find the website you want to visit.

How DNS Works:

• Request Initiation: When you type a domain name into your browser's address bar and press Enter, your computer initiates a DNS request. It first checks its own cache to see if it already knows the IP address for the domain. If not, it proceeds to step 2.
• Local DNS Server: If the IP address is not in the cache, your computer sends a request to a DNS server, typically provided by your internet service provider (ISP). This DNS server is like a librarian who has access to a much larger database of domain names and IP addresses.
• ·Recursive Search: If the local DNS server doesn't have the IP address, it starts a recursive search. It begins by asking other DNS servers if they know the IP address. If none of them do, they ask other servers, and so on, until the IP address is found.
• Response: Once a DNS server finds the IP address for the requested domain name, it sends it back to your computer. Your computer stores this information in its cache for future reference, speeding up the process next time you visit the same website.
• Connection: With the IP address in hand, your browser can now establish a connection to the server hosting the website you want to visit.
• Website Access: Your browser sends a request to the server using the IP address, asking for the specific webpage you requested. The server responds by sending back the webpage data, allowing your browser to display it on your screen.

Benefits of DNS:

• Efficiency: DNS helps in efficiently translating domain names into IP addresses, reducing the time it takes for you to access websites.
• Load Balancing: DNS can distribute traffic among multiple servers hosting the same website, helping to balance the load and ensure optimal performance.
• Redundancy: DNS servers are distributed worldwide, providing redundancy, and ensuring that the internet remains accessible even if some servers go offline.

2.?? TCP/IP (Transmission Control Protocol/Internet Protocol): is the backbone of the internet, providing a set of rules and protocols that govern how data is transmitted and received over networks. Here's a comprehensive explanation of TCP/IP:

Transmission Control Protocol (TCP):

TCP is responsible for breaking down data into smaller packets, ensuring that they are transmitted reliably and in the correct order. It establishes a connection between two devices, allowing them to exchange data. Key features of TCP include:

• Reliability: TCP ensures that data is delivered without errors and in the correct sequence by using acknowledgments and retransmissions.
• Flow Control: It regulates the flow of data between devices to prevent overwhelm, ensuring that the sender does not send data faster than the receiver can process it.
• Connection-Oriented: TCP establishes a connection between devices before data transfer begins, ensuring a reliable and orderly exchange of information.

Internet Protocol (IP):

IP is responsible for addressing and routing packets of data across networks. It assigns a unique IP address to each device connected to the internet, allowing data to be sent to the correct destination. Key features of IP include:

• Addressing: IP addresses identify devices on a network, allowing routers to forward data packets to the correct destination.
• Routing: IP routers use routing tables to determine the best path for data packets to reach their destination, considering factors like network congestion and reliability.
• Connectionless: Unlike TCP, IP is connectionless, meaning it does not establish a direct connection between devices before data transfer. Instead, it relies on routers to forward packets independently.

TCP/IP Protocol Stack:

TCP and IP work together as a protocol stack, with TCP handling the reliability and sequencing of data at the transport layer, while IP handles addressing and routing at the network layer. This layered approach allows for modular design and interoperability across different network technologies.

Application Layer Protocols:

TCP/IP also encompasses a suite of application layer protocols, including HTTP (Hypertext Transfer Protocol) for web browsing, FTP (File Transfer Protocol) for file transfer, SMTP (Simple Mail Transfer Protocol) for email communication, and many others. These protocols define how data is formatted, transmitted, and received at the application level.

Benefits of TCP/IP:

TCP/IP is the foundation of the modern internet, providing a standardized framework for communication between devices and networks. Its modular design, reliability mechanisms, and flexibility make it well-suited for a wide range of applications, from web browsing to email to streaming media.

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3.?? Firewall: A firewall is a security system that monitors and controls incoming and outgoing network traffic based on predetermined security rules. Here's a comprehensive explanation of how firewalls work and their importance:

Network Security:

Firewalls act as a barrier between a trusted internal network (like a corporate network or home network) and untrusted external networks (like the internet). They help prevent unauthorized access to or from the internal network while allowing legitimate communication to pass through.

Packet Filtering:

Firewalls inspect packets of data as they pass through the network. They compare each packet to a set of predetermined rules or criteria. If a packet meets the criteria defined in the firewall's rules, it's allowed to pass. If not, it's blocked or discarded.

Types of Firewalls:

• Packet Filtering Firewalls: These examine packets at the network level (Layer 3) of the OSI model, looking at information such as IP addresses, port numbers, and protocols.
• Stateful Inspection Firewalls: In addition to packet filtering, these firewalls maintain a record of active connections (state table). They analyze the state of each connection to determine whether incoming packets are part of an established or authorized connection.
• Proxy Firewalls: Proxy firewalls act as intermediaries between clients and servers. They receive requests from clients, forward them to the destination server, and then relay the responses back to the clients. This allows for more granular control and inspection of traffic.
• Next-Generation Firewalls (NGFW): NGFWs combine traditional firewall functionality with advanced security features such as intrusion prevention, application awareness, and deep packet inspection.

Application Layer Inspection:

Some firewalls can inspect traffic at the application layer (Layer 7) of the OSI model. They can analyze the contents of packets to detect and block specific types of applications or protocols, such as peer-to-peer file sharing or instant messaging.

Importance of Firewalls:

• Network Security: Firewalls play a crucial role in protecting networks from unauthorized access, cyber attacks, and malware.
• Access Control: They enforce security policies by controlling which network traffic is allowed and which is blocked.
• Visibility and Control: Firewalls provide visibility into network traffic, allowing administrators to monitor and analyze traffic patterns and identify potential security threats.
• Compliance: Many regulatory standards and compliance frameworks require organizations to implement firewalls as part of their network security measures.

4.?? HTTPS (Hypertext Transfer Protocol Secure): is a protocol used for secure communication over a computer network, commonly the internet. It ensures that the data transmitted between a web browser and a web server is encrypted and thus protected from interception or tampering by malicious parties.

How HTTPS Works:

• Client Request: When a user tries to access a website by entering its URL into a web browser, the browser sends a request to the web server hosting the site.
• SSL Handshake: If the website is configured to use HTTPS, the web server responds with its SSL (Secure Sockets Layer) certificate. The SSL certificate contains the server's public key, which is used for encryption, as well as other information about the website.
• Encryption: The web browser verifies the authenticity of the SSL certificate to ensure that it is legitimate and issued by a trusted Certificate Authority (CA). Once verified, the browser generates a session key and encrypts it using the server's public key. This session key is then sent to the server.
• Decryption: The web server receives the encrypted session key and decrypts it using its private key, which only the server possesses. This allows both the client and the server to have a shared secret for encrypted communication.
• Secure Communication: With the session key established, the client and server can now communicate securely. All data transmitted between them, including HTTP requests and responses, is encrypted using symmetric encryption algorithms. This means that even if intercepted, the data is unreadable without the session key.
• Data Exchange: The client and server exchange data as needed to load web pages, submit forms, or perform other actions on the website. Each piece of data is encrypted before transmission and decrypted upon receipt, ensuring its security throughout the communication process.

Benefits of HTTPS/SSL:

• Data Security: HTTPS ensures that sensitive information, such as login credentials, credit card numbers, and personal data, is encrypted during transmission, making it unreadable to anyone attempting to intercept it.
• Authentication: SSL certificates provide a means of authenticating the identity of websites, ensuring that users are communicating with the intended server and not an imposter.
• Integrity: HTTPS ensures the integrity of data by protecting it from tampering or modification during transmission. Any attempt to alter the encrypted data would result in decryption failure, alerting both the client and server to the tampering attempt.
• Trust: HTTPS increases user trust and confidence in websites by providing visual indicators, such as a padlock icon or green address bar, to signify that the connection is secure. Users are more likely to trust and engage with websites that use HTTPS.

5.?? Load Balancer: A load balancer is a networking device, hardware appliance, or software application that distributes incoming network traffic across multiple servers, ensuring optimal resource utilization, maximizing throughput, minimizing response time, and preventing overload on any single server. It acts as an intermediary between clients (such as web browsers or application users) and servers, efficiently distributing incoming requests to the most appropriate server based on various factors.

How Load Balancers Work:

• Traffic Distribution: Load balancers receive incoming requests from clients and distribute them across a pool of servers based on predefined algorithms and rules. These algorithms consider factors such as server health, current traffic load, server capacity, and session persistence to determine how to distribute incoming requests effectively.
• Health Monitoring: Load balancers continuously monitor the health and performance of servers in the server pool by periodically sending health checks or probes to each server. If a server becomes unavailable or unresponsive due to hardware failure, software crash, or other issues, the load balancer detects it and automatically removes the server from the pool, ensuring that incoming requests are not sent to the faulty server.
• Session Persistence: Some load balancers support session persistence, also known as sticky sessions, which ensure that all requests from a particular client are directed to the same server for the duration of the session. This is important for applications that store session data locally on a server and require subsequent requests from the same client to be handled by the same server to maintain session state.
• Scalability: Load balancers support horizontal scalability by allowing additional servers to be added to the server pool dynamically as traffic load increases. They can automatically scale up or scale down the number of servers based on demand, ensuring that the application can handle fluctuations in traffic without downtime or performance degradation.

Types of Load Balancers:

• Hardware Load Balancers: These are physical devices dedicated to load balancing and are often deployed in data centres or network infrastructure. Hardware load balancers offer high performance, scalability, and reliability but can be costly and require specialized expertise to manage.
• Software Load Balancers: These are software applications or virtual appliances that run on standard server hardware or virtual machines. Software load balancers offer flexibility, ease of deployment, and cost-effectiveness compared to hardware load balancers. Popular software load balancers include Nginx, HAProxy, and Apache Traffic Server.
• Cloud Load Balancers: Cloud service providers offer load balancing solutions as part of their platform services. Cloud load balancers are fully managed and scalable, allowing users to distribute traffic across virtual machines, containers, or serverless functions deployed on cloud infrastructure.

Benefits of Load Balancers:

• High Availability: Load balancers improve application availability and uptime by distributing traffic across multiple servers. If one server fails, the load balancer redirects traffic to the remaining healthy servers, ensuring uninterrupted service for users.
• Scalability: Load balancers enable applications to scale horizontally by distributing incoming traffic across a dynamic pool of servers. They can automatically scale up or down based on demand, allowing applications to handle increasing traffic loads without performance degradation.
• Performance Optimization: Load balancers optimize application performance by distributing requests to the server with the lowest current load, minimizing response time and ensuring optimal resource utilization.
• Fault Tolerance: Load balancers enhance application reliability and fault tolerance by detecting and isolating faulty servers from the server pool. They automatically reroute traffic away from failed servers, preventing service disruptions and maintaining consistent user experience.

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6.?? Web Server: A web server is a software application or hardware device that stores, processes, and delivers web pages, along with other web content, to clients (usually web browsers) over the internet or an intranet. It acts as the intermediary between the client and the server-side application, handling incoming HTTP (Hypertext Transfer Protocol) requests and responding with the requested web pages or resources.

Key Functions of a Web Server:

• Request Handling: Web servers receive HTTP requests from clients and process them according to predefined rules and configurations. They parse the request, identify the requested resource (such as a web page or file), and execute the appropriate actions to generate the response.
• Content Delivery: Web servers serve static and dynamic content to clients in response to HTTP requests. Static content, such as HTML files, images, and CSS stylesheets, is served directly from disk without any processing. Dynamic content, generated by server-side scripts or applications, is processed and generated on-the-fly before being sent to the client.
• Protocol Support: Web servers support various protocols, including HTTP, HTTPS (HTTP over SSL/TLS for secure communication), and FTP (File Transfer Protocol), allowing clients to access web resources securely and efficiently.
• Configuration and Security: Web servers are configured with settings that define how they handle incoming requests, manage resources, and enforce security policies. They implement security features such as access control, authentication, and encryption to protect sensitive data and prevent unauthorized access.

7.?? Application Server: An application server is a software framework or platform that provides the runtime environment for executing and managing web applications. It hosts and manages the business logic, application code, and data processing tasks required by the application. Application servers facilitate communication between the client-side interface (such as a web browser) and backend databases or other resources.

Key Functions of an Application Server:

• Application Execution: Application servers execute the code and business logic of web applications, handling user requests and generating dynamic content. They support various programming languages and frameworks, such as Java EE (Enterprise Edition), .NET, PHP, Python, and Ruby on Rails.
• Database Connectivity: Application servers interact with backend databases to retrieve and manipulate data required by the application. They establish connections to databases, execute SQL queries, and process database transactions to retrieve, insert, update, or delete data.
• Session Management: Application servers manage user sessions and session state, maintaining information about user interactions and preferences across multiple requests. They use techniques such as session cookies, URL rewriting, and server-side session storage to store and manage session data securely.
• Scalability and Load Balancing: Application servers support horizontal scalability by distributing incoming traffic across multiple server instances or nodes. They can work in conjunction with load balancers to distribute requests evenly and efficiently, ensuring optimal performance and resource utilization.

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8.?? Database: A database is an organized collection of structured data stored electronically in a computer system. It is designed to efficiently manage, retrieve, and manipulate data according to predefined rules and relationships. Databases provide a centralized repository for storing and accessing data, enabling applications to store, retrieve, and update information securely and efficiently.

Key Components of a Database:

• Tables: Databases organize data into tables, which consist of rows and columns. Each row represents a record or data entity, and each column represents a specific attribute or field of the record. Tables define the structure of the data and the relationships between different data entities.
• Schema: The schema defines the structure of the database, including the tables, fields, data types, constraints, and relationships between tables. It serves as a blueprint for organizing and storing data in the database, ensuring consistency and integrity.
• Queries: Queries are commands or statements used to retrieve, manipulate, or analyze data stored in the database. They allow users to perform operations such as selecting specific data, filtering records, sorting results, and aggregating data using functions and operators.
• Indexes: Indexes are data structures used to optimize the performance of database queries by providing fast access to specific data values. They allow the database system to locate records quickly based on indexed columns, reducing the time required to retrieve data and improve query performance.
• Constraints: Constraints are rules or conditions imposed on data to maintain data integrity and enforce data validation rules. Common constraints include primary keys, foreign keys, unique constraints, check constraints, and default values, ensuring that data meets certain criteria and adheres to predefined rules.
• Transactions: Transactions are units of work performed on the database that involve one or more operations, such as inserting, updating, or deleting data. Transactions ensure the atomicity, consistency, isolation, and durability (ACID properties) of database operations, guaranteeing that transactions are processed reliably and securely.

Types of Databases:

• Relational Databases: Relational databases organize data into tables with predefined relationships between them. They use structured query language (SQL) to manipulate data and perform operations such as querying, updating, and deleting records. Examples of relational databases include MySQL, PostgreSQL, Oracle Database, Microsoft SQL Server, and SQLite.
• NoSQL Databases: NoSQL (Not Only SQL) databases are non-relational databases that provide flexible data models and scalability for handling large volumes of unstructured or semi-structured data. They support various data models, including document-oriented, key-value, columnar, and graph databases. Examples of NoSQL databases include MongoDB, Cassandra, Redis, Couchbase, and Amazon DynamoDB.
• In-Memory Databases: In-memory databases store data primarily in memory (RAM) rather than on disk, enabling faster data access and processing. They are designed for high-performance applications that require low-latency data retrieval and real-time analytics. Examples of in-memory databases include Redis, Memcached, and Apache Ignite.

Benefits of Databases:

• Data Organization: Databases provide a structured framework for organizing and storing data, making it easier to manage and access information efficiently.
• Data Integrity: Databases enforce data integrity through constraints, ensuring that data is accurate, consistent, and valid according to predefined rules and relationships.
• Data Security: Databases implement security features such as access control, authentication, encryption, and auditing to protect sensitive data and prevent unauthorized access.
• Data Scalability: Databases support horizontal and vertical scalability, allowing them to handle increasing volumes of data and accommodate growing user demands without sacrificing performance or reliability.
• Data Recovery: Databases implement backup and recovery mechanisms to protect against data loss and ensure data availability in the event of hardware failure, software errors, or other disasters.

In summary, when you type "https://www.google.com" (or any other web address) in your browser and press Enter, your computer goes through a series of steps involving DNS lookup, establishing a secure connection using TCP/IP and HTTPS/SSL, passing through firewalls and load balancers, interacting with web servers and application servers, and potentially accessing databases to retrieve and deliver the requested web page or content.

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