What happens when you type an URL in the browser and press Enter?

1. URL Parsing: The browser parses the URL to identify the protocol (such as HTTP or HTTPS), the domain name (like www.google.com), and the path to the specific resource (like /index.html).
2. DNS Lookup: The browser checks its cache to see if it already knows the IP address associated with the domain name. If not, it sends a DNS (Domain Name System) lookup request to a DNS server to find the IP address corresponding to the domain name.
3. TCP Connection: Once the browser has the IP address, it initiates a TCP (Transmission Control Protocol) connection with the server at that IP address. This involves a three-way handshake between the browser and the server to establish the connection.
4. HTTP Request: After the TCP connection is established, the browser sends an HTTP (Hypertext Transfer Protocol) request to the server. This request includes information such as the specific resource being requested (e.g., /index.html), any additional headers, and other metadata.
5. Server Processing: The server receives the HTTP request and processes it. This may involve accessing the requested resource from the server's file system or executing code (if the resource is a dynamic webpage).
6. HTTP Response: Once the server has processed the request, it sends back an HTTP response to the browser. This response includes the requested resource (such as an HTML file), along with metadata like the response status code, content type, and any cookies or other headers.
7. Rendering: The browser receives the HTTP response and begins to render the webpage. It parses the HTML content to build the Document Object Model (DOM), fetches additional resources like CSS stylesheets and JavaScript files, and finally renders the webpage on the screen.
8. Display: The rendered webpage is displayed in the browser window, allowing the user to interact with its contents.

Throughout this process, there may be additional steps such as SSL/TLS negotiation for secure connections (HTTPS), caching mechanisms to optimize performance, and content compression to reduce data transfer times. But these are the fundamental steps involved in loading a webpage after typing a URL into the browser.

When you type the URL in the search bar and click enter, The browser breaks down the URL as illustrated above. Next, the browser has to figure out the IP address of the server responsible for hosting the website. The browser will initially search its cached data for the IP address associated with the URL provided. If the required IP address is not found, Then the browser performs a DNS query where the user's computer (DNS client) asks the DNS server for the IP address associated with the provided URL.

Load Balancer

is a critical component in distributed computing and networking infrastructure. Its primary function is to efficiently distribute incoming network traffic (such as HTTP requests in the context of web applications) across multiple servers or resources. Here's how it works:

1. Traffic Distribution: When a client makes a request to access a web application, it first interacts with the load balancer. The load balancer acts as an intermediary between the client and the backend servers.
2. Health Checking: Before forwarding the request to any backend server, the load balancer typically performs health checks on these servers to ensure they are operational and capable of handling requests. If a server is found to be unhealthy or overloaded, the load balancer can route traffic away from it.
3. Load Distribution Algorithms: Load balancers use various algorithms to distribute incoming traffic across backend servers. Common algorithms include Round Robin, Least Connections, IP Hashing, and Least Response Time. These algorithms help ensure optimal utilization of resources and prevent any single server from being overloaded while others remain idle.
4. Session Persistence: In some cases, it's necessary to maintain session persistence or "sticky sessions" for certain types of requests, such as those associated with a user's session in a web application. Load balancers can be configured to ensure that requests from the same client are consistently routed to the same backend server, thus preserving session state.
5. Scalability and High Availability: Load balancers play a crucial role in ensuring scalability and high availability of web applications. By distributing traffic across multiple servers, they enable applications to handle increased load without degradation in performance. Additionally, load balancers themselves can be deployed in redundant configurations to eliminate single points of failure.
6. Security: Load balancers can also enhance security by acting as a barrier between external clients and internal servers. They can perform functions like SSL termination, DDoS (Distributed Denial of Service) protection, and web application firewalling to protect against various types of attacks.

Overall, load balancers are essential for optimizing the performance, reliability, and security of modern web applications by efficiently distributing traffic across backend servers.

DATABASE MANAGEMENT SYSTEM - DBMS

DBMS plays a crucial role in organizing, storing, and managing data efficiently, ensuring data integrity, security, and availability, and providing a platform for applications to access and manipulate data effectively.

FIREWALL

A digital security system that scrutinizes all incoming and outgoing traffic on a network according to a defined set of rules. A firewall blocks unauthorized traffic and allows only communications that are considered safe, using a set of security rules provided by a network administrator.

WEB & APPLICATION SERVER

A web server refers to software and hardware that uses HTTP (Hypertext Transfer Protocol) and other protocols to respond to client requests made over the World Wide Web. An application server is a modern form of platform middleware. This is system software that resides between the operating system (OS), and the external resources (such as a database management system [DBMS], communications, and Internet services). An application server exposes business logic to the clients, which generates dynamic content. It is a software framework that transforms data to provide the specialized functionality offered by a business, service, or application.