HyperText Transfer Protocol (HTTP) defines the standard rules that web browsers and servers use to request and exchange web pages and resources across a network.

HTTP follows a straightforward client-server request-response pattern. A client, such as a web browser, initiates communication by sending a request (such as a request to retrieve a home page), and the web server returns the requested HTML, images, and associated files in its response.

Because HTTP requires accurate and complete data delivery, it runs on top of TCP, which provides reliable, ordered transmission. Web servers handling standard HTTP traffic typically listen on port 80.

HTTP and the Request-Response Model

HTTPS is standard HTTP wrapped in Transport Layer Security (TLS) encryption. It provides a secure communication channel between web browsers and servers, making modern websites secure by default.

The primary purpose of wrapping HTTP in TLS is privacy and integrity. Encryption ensures that data in transit cannot be intercepted, read, or tampered with by unauthorized parties between the client and the server.

While standard HTTP services run on port 80, web servers configured for encrypted HTTPS traffic typically listen on port 443.

HTTPS and TLS Encryption

Loading a secure web page involves multiple protocols working together in a precise, multi-step sequence that showcases the layered networking model:

1. **DNS Lookup**: The client queries a DNS server to resolve the human-readable domain name into a numeric IP address.
2. **TCP Handshake**: The browser establishes a reliable transport connection to the destination IP using the three-way handshake (SYN, SYN-ACK, ACK).
3. **TLS Setup**: For an HTTPS connection, the browser and server negotiate encryption keys to secure the session.
4. **HTTP Request and Response**: The browser submits an HTTP request (such as `GET`), and the server replies with the requested files.
5. **Rendering**: The browser processes the returned HTML, styling, and assets to render the complete page.

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