Hypertext Transfer Protocol

Hypertext Transfer Protocol is an application-layer protocol fundamental to data communication across the World Wide Web. Developed initially by Tim Berners-Lee at CERN, it functions as a request-response protocol in the client-server computing model. The protocol's design enables the transfer of hypermedia documents, forming the foundation for web browsers to retrieve resources from servers.

Overview

The protocol operates as a stateless system where each request from a client, such as a web browser, is treated independently by a server like Apache HTTP Server. This model underpins the architecture of the World Wide Web, allowing for the distributed and interconnected nature of information. Key concepts include the use of URLs to specify resources and methods like GET and POST to define actions. The foundational work is standardized by the Internet Engineering Task Force and the World Wide Web Consortium.

Technical specification

Communication occurs through a structured exchange of text-based messages. A client sends a request message containing a method, a URI, and a protocol version, followed by header fields. The server responds with a status line, including codes like 404 or 200, and its own headers, often concluding with the requested resource. Header fields manage aspects such as Content-Type, Cache-Control, and session cookies, which introduce stateful behavior. The protocol commonly operates over Transmission Control Protocol connections on port 80.

Versions

The original version, defined in 1991, was quickly succeeded by HTTP/1.0, formalized in RFC 1945. The widely adopted HTTP/1.1, standardized in RFC 2616, introduced persistent connections and chunked transfer encoding. A major revision, HTTP/2, published as RFC 7540, added multiplexing and header compression for performance. The most recent standard, HTTP/3, shifts from Transmission Control Protocol to QUIC, a transport protocol built on User Datagram Protocol. Each iteration has been developed within the Internet Engineering Task Force to address evolving web performance and security needs.

Security

The basic protocol transmits data in plaintext, making communications vulnerable to eavesdropping and manipulation. To address this, HTTPS was created by layering the protocol within Transport Layer Security or its predecessor, Secure Sockets Layer. This encryption is critical for securing transactions on sites like Amazon and PayPal, and for protecting user privacy. Enforcement of HTTPS is championed by organizations like the Electronic Frontier Foundation and is a ranking factor for search engines like Google Search.

Applications and impact

Beyond fetching HTML web pages, the protocol is the backbone for APIs, enabling services from Twitter to Spotify to function. It is integral to the architecture of Cloud computing platforms such as Amazon Web Services and Microsoft Azure. The protocol's simplicity and ubiquity fueled the growth of companies like Facebook and Netflix, fundamentally reshaping global commerce, media, and social interaction. Its ongoing evolution continues to influence developments in the Internet of Things and edge computing.

Category:Internet protocols Category:World Wide Web Category:Application layer protocols