Introduction
In today's digital age, we often take for granted the seamless experience of accessing websites with just a few clicks or taps. However, behind this seemingly simple action lies a complex series of processes and interactions between various web infrastructure components.
Have you ever wondered what happens when you type https://www.google.com
into your browser's address bar and press Enter
? In this article, we'll journey to demystify the intricate steps involved, shedding light on the magic behind the scenes.
The journey begins with your browser reaching out to a Domain Name System (DNS) server to translate the human-readable domain name (www.google.com
) into an IP address that machines can understand. This process is analogous to looking up a phone number in a directory before making a call.
Understanding DNS
The DNS is a hierarchical and decentralized system that acts as the internet's phone book, mapping domain names to their corresponding IP addresses. When you enter a domain name into your browser, it sends a request to a DNS server to obtain the IP address associated with that domain.
The DNS is organized into different levels, with the root servers at the top, followed by Top-Level Domain (TLD) servers, and then Authoritative Name Servers responsible for specific domains. This hierarchical structure allows for efficient distribution and caching of domain-to-IP mappings, ensuring fast resolution times.
The DNS Lookup Process
.com
, .org
, .net
).With the IP address obtained, your browser can now initiate a connection with the server hosting the website.
The Transmission Control Protocol/Internet Protocol (TCP/IP) suite governs how data is transmitted over the internet, ensuring reliable and ordered delivery of packets between your browser and the web server.
TCP's Three-Way Handshake
Before data can be exchanged, your browser and the web server establish a TCP connection through a process called the "three-way handshake":
IP Routing and Packet Delivery
With the TCP connection established, data can be transmitted between your browser and the web server using the Internet Protocol (IP). IP addresses uniquely identify devices on the internet, allowing routers to forward data packets along the most efficient path to their destinations.
Routers examine the destination IP address in each packet and use routing tables to determine the next hop in the journey. This process continues until the packets reach the web server's network, where they are reassembled in the correct order based on the TCP sequence numbers.
Before the request reaches the web server, it must pass through a firewall – a security system that monitors incoming and outgoing network traffic. The firewall acts as a gatekeeper, inspecting each packet against a predefined set of rules to determine whether to allow or block it.
Firewall Rules and Policies
Firewall rules are based on factors such as the source and destination IP addresses, ports, protocols, and other criteria. These rules protect the server from potential threats, such as malicious attacks, unauthorized access attempts, and other malicious activities.
The incoming request can proceed to the web server if it adheres to the firewall's rules. However, if the request violates the rules, it is blocked, and an appropriate response (e.g., an error message) is sent back to the client.
Since you entered https://www.google.com
, your browser establishes a secure connection using the Hypertext Transfer Protocol Secure (HTTPS) and Secure Sockets Layer/Transport Layer Security (SSL/TLS) protocol. This encryption ensures that the data exchanged between your browser and the server remains private and secure, protecting it from eavesdropping and tampering.
SSL/TLS Handshake
Before data can be transmitted securely, your browser and the web server perform an SSL/TLS handshake to establish an encrypted communication channel:
HTTPS and SSL/TLS Benefits
HTTPS and SSL/TLS encryption provide several benefits, including:
Large websites like Google receive an immense amount of traffic from users around the globe. To handle this load efficiently and ensure high availability, they employ load balancers – systems that distribute incoming traffic across multiple web servers.
How Load Balancers Work
Load balancers are intermediaries between clients (your browser) and the web servers hosting the website. When a request arrives, the load balancer determines which web server should handle it based on various load-balancing algorithms and server health checks.
Common load-balancing algorithms include:
Load balancers continuously monitor the health and availability of the web servers, automatically rerouting traffic away from failed or overloaded servers to maintain service availability and performance.
Benefits of Load Balancing
Load balancing provides several benefits, including:
Once your request has navigated through the load balancer, it reaches one of the available web servers responsible for processing and serving the requested content. The web server acts as the backbone of the website, handling incoming requests and delivering the appropriate responses.
Web servers are powered by software that handles HTTP/HTTPS requests and responses. Some popular web server software options include:
These web server software applications are responsible for interpreting incoming requests, processing them, and generating appropriate responses.
If the requested resource is a static file (e.g., HTML, CSS, JavaScript, images), the web server can directly serve the file from its file system or cache. This process is straightforward: the web server reads the requested file and returns it to your browser.
Dynamic Content Generation
However, many websites nowadays rely on dynamic content generated on the fly based on user input, personalization, or data retrieval from databases. In these cases, the web server may delegate the request processing to an application server.
Application Server Interaction
Application servers execute server-side logic, process user input, and interact with databases or other data sources to generate dynamic content. Common application server technologies include:
When the web server receives a request for dynamic content, it forwards it to the appropriate application server for processing. The application server executes the necessary code (e.g., Java, .NET, Node.js, PHP) and retrieves the required data from databases or other sources.
For example, when you search on Google, the web server receives your request. It passes it to the application server, which interacts with Google's search index and algorithms to dynamically generate the relevant search results.
Many websites rely on databases to store and retrieve data efficiently. In the case of dynamic content generation, the application server may need to interact with one or more databases to fetch or update data.
Common database management systems (DBMS) used in web applications include:
The application server establishes a connection with the database, executes queries (e.g., SQL for relational databases, document-based queries for NoSQL databases), and retrieves or manipulates the necessary data.
For example, when you log into a website, the application server might query a user database to verify your credentials and fetch your user profile data.
Once the application server has processed the request and gathered the necessary data, it generates the appropriate response (e.g., HTML, JSON, XML) and sends it back to the web server. The web server, in turn, forwards the response to your browser over the established HTTPS connection.
Your browser then receives the response, parses the HTML, CSS, and JavaScript, and renders the website content on your screen, providing the final result of your initial request.
Throughout this intricate process, various components work in harmony, ensuring that your request is securely handled, processed efficiently, and delivered to your browser in a timely and reliable manner.
Источник: dev.to
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