Hypertext Transfer Protocol

The Hypertext Transfer Protocol (HTTP) is a fundamental protocol used for transferring hypermedia documents, such as HTML, across the World Wide Web. HTTP serves as an application layer protocol in the Internet protocol suite, which operates over the Internet and facilitates distributed, collaborative, hypermedia information systems.

HTTP was originally developed by Tim Berners-Lee at CERN and has since evolved through several versions, the most recent being HTTP/3. The protocol is stateless, meaning each request from a client to the server is treated independently without retaining user session information between connections.

Operation

Request-Response Model

HTTP functions via a request-response model. A client, typically a web browser, sends an HTTP request to the server, which then responds with the requested resource or an error message. The request and response messages leverage HTTP headers to convey additional context for the transaction, such as format and content-type.

Methods

HTTP supports various methods, with the most common being:

• GET: Requests a representation of the specified resource.
• POST: Submits data to the server.
• PUT: Updates a specified resource.
• DELETE: Removes the specified resource.

Status Codes

HTTP status codes are issued by a server in response to a client's request. These codes are categorized into five classes, including:

• 1xx: Informational responses
• 2xx: Successful responses
• 3xx: Redirection messages
• 4xx: Client error responses (e.g., HTTP 404)
• 5xx: Server error responses

Security Enhancements

HTTPS

The Hypertext Transfer Protocol Secure (HTTPS) is an extension of HTTP that encrypts data transfers using Transport Layer Security (TLS). This ensures secure communications, particularly for online transactions and personal data exchanges.

HTTP Strict Transport Security

HTTP Strict Transport Security (HSTS) is a policy mechanism that helps protect websites against man-in-the-middle attacks by enforcing secure HTTPS connections.

Extensions and Related Protocols

• HTTP/2: A major revision that improves performance by allowing multiple simultaneous streams of data.
• SOAP: A protocol that uses HTTP for message transmission, typically in web services.

Related Topics

• WebSocket, for full-duplex communication over a single TCP connection using HTTP.
• Domain Name System over HTTPS (DoH), for secure DNS resolution.
• Session Initiation Protocol, which incorporates elements of HTTP for initiating and managing communication sessions.

HTTP remains a cornerstone of the internet, continuously evolving to meet the demands of a rapidly changing web environment. Its ability to adapt with enhancements like HTTPS and HTTP/2 demonstrates its critical role in digital communications.