Early research and development:
48-596: Merging the networks and creating the Internet: Commercialization, privatization, broader access leads to the modern Internet: Examples of Internet services: HTTP/3 is the third major version of the Hypertext Transfer Protocol used to exchange information on the World Wide Web , complementing the widely-deployed HTTP/1.1 and HTTP/2 . Unlike previous versions which relied on
96-492: A Proposed Standard in RFC 9114 . HTTP semantics are consistent across versions: the same request methods , status codes , and message fields are typically applicable to all versions. The differences are in the mapping of these semantics to underlying transports. Both HTTP/1.1 and HTTP/2 use TCP as their transport. HTTP/3 uses QUIC , a transport layer network protocol which uses user space congestion control over
144-407: A mouse click or by tapping the screen in a web browser . Development of HTTP was initiated by Tim Berners-Lee at CERN in 1989 and summarized in a simple document describing the behavior of a client and a server using the first HTTP version, named 0.9. That version was subsequently developed, eventually becoming the public 1.0. Development of early HTTP Requests for Comments (RFCs) started
192-453: A queue of packets is held up by the first packet in the queue. This occurs, for example, in input-buffered network switches , out-of-order delivery and multiple requests in HTTP pipelining . A switch may be composed of buffered input ports, a switch fabric, and buffered output ports. If first-in first-out (FIFO) input buffers are used, only the oldest packet is available for forwarding. If
240-439: A batch of RFCs was published, deprecating many of the previous documents and introducing a few minor changes and a refactoring of HTTP semantics description into a separate document. HTTP is a stateless application-level protocol and it requires a reliable network transport connection to exchange data between client and server. In HTTP implementations, TCP/IP connections are used using well-known ports (typically port 80 if
288-430: A client user interface called web browser . Berners-Lee designed HTTP in order to help with the adoption of his other idea: the "WorldWideWeb" project, which was first proposed in 1989, now known as the World Wide Web . The first web server went live in 1990. The protocol used had only one method, namely GET, which would request a page from a server. The response from the server was always an HTML page. In 1991,
336-474: A client failing to properly encode the request-target. Since 2016 many product managers and developers of user agents (browsers, etc.) and web servers have begun planning to gradually deprecate and dismiss support for HTTP/0.9 protocol, mainly for the following reasons: In 2020, the first drafts HTTP/3 were published and major web browsers and web servers started to adopt it. On 6 June 2022, IETF standardized HTTP/3 as RFC 9114 . In June 2022,
384-421: A far future version of HTTP called HTTP-NG (HTTP Next Generation) that would have solved all remaining problems, of previous versions, related to performances, low latency responses, etc. but this work started only a few years later and it was never completed. In May 1996, RFC 1945 was published as a final HTTP/1.0 revision of what had been used in previous 4 years as a pre-standard HTTP/1.0-draft which
432-643: A few years later in a coordinated effort by the Internet Engineering Task Force (IETF) and the World Wide Web Consortium (W3C), with work later moving to the IETF. HTTP/1 was finalized and fully documented (as version 1.0) in 1996. It evolved (as version 1.1) in 1997 and then its specifications were updated in 1999, 2014, and 2022. Its secure variant named HTTPS is used by more than 85% of websites. HTTP/2 , published in 2015, provides
480-482: A globally routable address, by relaying messages with external servers. To allow intermediate HTTP nodes (proxy servers, web caches, etc.) to accomplish their functions, some of the HTTP headers (found in HTTP requests/responses) are managed hop-by-hop whereas other HTTP headers are managed end-to-end (managed only by the source client and by the target web server). HTTP is an application layer protocol designed within
528-496: A lossy network among a large number of peers is a difficult problem. While atomic broadcast algorithms solve the single point of failure problem of centralized servers, those algorithms introduce a head-of-line blocking problem. The Bimodal Multicast algorithm, a randomized algorithm that uses a gossip protocol , avoids head-of-line blocking by allowing some messages to be received out-of-order. One form of HOL blocking in HTTP/1.1
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#1732935203311576-456: A message that was sent earlier. This affects, for example, HTTP/2 , which frames multiple request–response pairs onto a single stream; HTTP/3 , which has an application-layer framing design and uses datagram rather than stream transport, avoids this problem. The latency degradation from head-of-line blocking depends on the underlying packet loss rate and round-trip time , with higher losses producing worse latency. Without changing
624-421: A more efficient expression of HTTP's semantics "on the wire". As of August 2024, it is supported by 66.2% of websites (35.3% HTTP/2 + 30.9% HTTP/3 with backwards compatibility) and supported by almost all web browsers (over 98% of users). It is also supported by major web servers over Transport Layer Security (TLS) using an Application-Layer Protocol Negotiation (ALPN) extension where TLS 1.2 or newer
672-536: A server establishing a connection (real or virtual). An HTTP(S) server listening on that port accepts the connection and then waits for a client's request message. The client sends its HTTP request message. Upon receiving the request the server sends back an HTTP response message, which includes header(s) plus a body if it is required. The body of this response message is typically the requested resource, although an error message or other information may also be returned. At any time (for many reasons) client or server can close
720-540: Is a revision of previous HTTP/2 in order to use QUIC + UDP transport protocols instead of TCP. Before that version, TCP/IP connections were used; but now, only the IP layer is used (which UDP, like TCP, builds on). This slightly improves the average speed of communications and to avoid the occasional (very rare) problem of TCP connection congestion that can temporarily block or slow down the data flow of all its streams (another form of " head of line blocking "). The term hypertext
768-453: Is an accepted version of this page HTTP ( Hypertext Transfer Protocol ) is an application layer protocol in the Internet protocol suite model for distributed, collaborative, hypermedia information systems. HTTP is the foundation of data communication for the World Wide Web , where hypertext documents include hyperlinks to other resources that the user can easily access, for example by
816-401: Is required. HTTP/3 , the successor to HTTP/2, was published in 2022. As of February 2024, it is now used on 30.9% of websites and is supported by most web browsers, i.e. (at least partially) supported by 97% of users. HTTP/3 uses QUIC instead of TCP for the underlying transport protocol. Like HTTP/2, it does not obsolete previous major versions of the protocol. Support for HTTP/3
864-411: Is the only HTTP version deployed). As of September 2024, HTTP/3 is supported by 95% of major web browsers (though not enabled for all Safari users) and 31% of the top 10 million websites. It has been supported by Chromium (and derived projects including Google Chrome , Microsoft Edge , Samsung Internet , and Opera ) since April 2020 and by Mozilla Firefox since May 2021. Safari 14 implemented
912-454: Is unnecessary; all buffering is handled at outputs and HOL blocking is avoided. This no-input-buffering architecture is common in small to medium-sized ethernet switches . Out-of-order delivery occurs when sequenced packets arrive out of order. This may happen due to different paths taken by the packets or from packets being dropped and resent. HOL blocking can significantly increase packet reordering. Reliably broadcasting messages across
960-509: Is when the number of allowed parallel requests in the browser is used up, and subsequent requests need to wait for the former ones to complete. HTTP/2 addresses this issue through request multiplexing, which eliminates HOL blocking at the application layer, but HOL still exists at the transport (TCP) layer. Head-of-line blocking can occur in reliable byte streams : if packets are reordered or lost and need to be retransmitted (and thus arrive out-of-order), data from sequentially later parts of
1008-519: The User Datagram Protocol (UDP). The switch to QUIC aims to fix a major problem of HTTP/2 called " head-of-line blocking ": because the parallel nature of HTTP/2's multiplexing is not visible to TCP's loss recovery mechanisms , a lost or reordered packet causes all active transactions to experience a stall regardless of whether that transaction was impacted by the lost packet. Because QUIC provides native multiplexing, lost packets only impact
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#17329352033111056-422: The client whereas a process , named web server , running on a computer hosting one or more websites may be the server . The client submits an HTTP request message to the server. The server, which provides resources such as HTML files and other content or performs other functions on behalf of the client, returns a response message to the client. The response contains completion status information about
1104-719: The HTTP Working Group released an updated six-part HTTP/1.1 specification obsoleting RFC 2616 : In RFC 7230 Appendix-A, HTTP/0.9 was deprecated for servers supporting HTTP/1.1 version (and higher): Since HTTP/0.9 did not support header fields in a request, there is no mechanism for it to support name-based virtual hosts (selection of resource by inspection of the Host header field). Any server that implements name-based virtual hosts ought to disable support for HTTP/0.9 . Most requests that appear to be HTTP/0.9 are, in fact, badly constructed HTTP/1.x requests caused by
1152-444: The connection is unencrypted or port 443 if the connection is encrypted, see also List of TCP and UDP port numbers ). In HTTP/2, a TCP/IP connection plus multiple protocol channels are used. In HTTP/3, the application transport protocol QUIC over UDP is used. Data is exchanged through a sequence of request–response messages which are exchanged by a session layer transport connection. An HTTP client initially tries to connect to
1200-489: The connection. Closing a connection is usually advertised in advance by using one or more HTTP headers in the last request/response message sent to server or client. In HTTP/0.9 , the TCP/IP connection is always closed after server response has been sent, so it is never persistent. Head-of-line blocking Head-of-line blocking ( HOL blocking ) in computer networking is a performance-limiting phenomenon that occurs when
1248-416: The establishment of TCP connections presents considerable overhead, especially under high traffic conditions. HTTP/2 is a revision of previous HTTP/1.1 in order to maintain the same client–server model and the same protocol methods but with these differences in order: HTTP/2 communications therefore experience much less latency and, in most cases, even higher speeds than HTTP/1.1 communications. HTTP/3
1296-443: The first documented official version of HTTP was written as a plain document, less than 700 words long, and this version was named HTTP/0.9, which supported only GET method, allowing clients to only retrieve HTML documents from the server, but not supporting any other file formats or information upload. Since 1992, a new document was written to specify the evolution of the basic protocol towards its next full version. It supported both
1344-663: The framework of the Internet protocol suite . Its definition presumes an underlying and reliable transport layer protocol. In HTTP/3 , the Transmission Control Protocol (TCP) is no longer used, but the older versions are still more used and they most commonly use TCP. They have also been adapted to use unreliable protocols such as the User Datagram Protocol (UDP), which HTTP/3 also (indirectly) always builds on, for example in HTTPU and Simple Service Discovery Protocol (SSDP). HTTP resources are identified and located on
1392-502: The group stopped its activity passing the technical problems to IETF. In 2007, the IETF HTTP Working Group (HTTP WG bis or HTTPbis) was restarted firstly to revise and clarify previous HTTP/1.1 specifications and secondly to write and refine future HTTP/2 specifications (named httpbis). In 2009, Google , a private company, announced that it had developed and tested a new HTTP binary protocol named SPDY . The implicit aim
1440-458: The need to start to focus on a new HTTP/2 protocol (while finishing the revision of HTTP/1.1 specifications), maybe taking in consideration ideas and work done for SPDY. After a few months about what to do to develop a new version of HTTP, it was decided to derive it from SPDY. In May 2015, HTTP/2 was published as RFC 7540 and quickly adopted by all web browsers already supporting SPDY and more slowly by web servers. In June 2014,
1488-706: The network by Uniform Resource Locators (URLs), using the Uniform Resource Identifiers (URIs) schemes http and https . As defined in RFC 3986 , URIs are encoded as hyperlinks in HTML documents, so as to form interlinked hypertext documents. In HTTP/1.0 a separate TCP connection to the same server is made for every resource request. In HTTP/1.1 instead a TCP connection can be reused to make multiple resource requests (i.e. of HTML pages, frames, images, scripts , stylesheets , etc.). HTTP/1.1 communications therefore experience less latency as
HTTP/3 - Misplaced Pages Continue
1536-498: The new versions of browsers and servers was rapid. In March 1996, one web hosting company reported that over 40% of browsers in use on the Internet used the new HTTP/1.1 header "Host" to enable virtual hosting , and that by June 1996, 65% of all browsers accessing their servers were pre-standard HTTP/1.1 compliant. In January 1997, RFC 2068 was officially released as HTTP/1.1 specifications. In June 1999, RFC 2616
1584-423: The oldest packet cannot be transmitted due to its target output being busy, then more recent arrivals cannot be forwarded. The output may be busy if there is output contention . Without HOL blocking, the new arrivals could potentially be forwarded around the stuck oldest packet to their respective destinations. HOL blocking can produce performance-degrading effects in input-buffered systems. This phenomenon limits
1632-604: The protocol but it remains disabled by default. HTTP/3 originates from an Internet Draft adopted by the QUIC working group. The original proposal was named "HTTP/2 Semantics Using The QUIC Transport Protocol", and later renamed "Hypertext Transfer Protocol (HTTP) over QUIC". On 28 October 2018 in a mailing list discussion, Mark Nottingham, Chair of the IETF HTTP and QUIC Working Groups, proposed renaming HTTP-over-QUIC to HTTP/3, to "clearly identify it as another binding of HTTP semantics to
1680-811: The request and may also contain requested content in its message body. A web browser is an example of a user agent (UA). Other types of user agent include the indexing software used by search providers ( web crawlers ), voice browsers , mobile apps , and other software that accesses, consumes, or displays web content. HTTP is designed to permit intermediate network elements to improve or enable communications between clients and servers. High-traffic websites often benefit from web cache servers that deliver content on behalf of upstream servers to improve response time. Web browsers cache previously accessed web resources and reuse them, whenever possible, to reduce network traffic. HTTP proxy servers at private network boundaries can facilitate communication for clients without
1728-417: The simple request method of the 0.9 version and the full GET request that included the client HTTP version. This was the first of the many unofficial HTTP/1.0 drafts that preceded the final work on HTTP/1.0. After having decided that new features of HTTP protocol were required and that they had to be fully documented as official RFCs , in early 1995 the HTTP Working Group (HTTP WG, led by Dave Raggett )
1776-434: The stream may be received before sequentially earlier parts of the stream; however, the later data cannot typically be used until the earlier data has been received, incurring network latency . If multiple independent higher-level messages are encapsulated and multiplexed onto a single reliable byte stream, then head-of-line blocking can cause processing of a fully-received message that was sent later to wait for delivery of
1824-589: The streams where data has been lost. Proposed DNS resource records SVCB (service binding) and HTTPS would allow connecting without first receiving the Alt-Svc header via previous HTTP versions, therefore removing the 1 RTT of handshaking of TCP. There is client support for HTTPS resource records since Firefox 92, iOS 14, reported Safari 14 support, and Chromium supports it behind a flag. Open-source libraries that implement client or server logic for QUIC and HTTP/3 include Hypertext Transfer Protocol This
1872-414: The throughput of switches. For FIFO input buffers, a simple model of fixed-sized cells to uniformly distributed destinations, causes the throughput to be limited to 58.6% of the total as the number of links becomes large. One way to overcome this limitation is by using virtual output queues . Only switches with input buffering can suffer HOL blocking. With sufficient internal bandwidth, input buffering
1920-612: The well-established TCP (published in 1974), HTTP/3 uses QUIC (officially introduced in 2021), a multiplexed transport protocol built on UDP . HTTP/3 uses similar semantics compared to earlier revisions of the protocol, including the same request methods , status codes , and message fields , but encodes them and maintains session state differently. However, partially due to the protocol's adoption of QUIC, HTTP/3 has lower latency and loads more quickly in real-world usage when compared with previous versions: in some cases over four times as fast than with HTTP/1.1 (which, for many websites,
1968-483: The wire protocol [...] so people understand its separation from QUIC". Nottingham's proposal was accepted by fellow IETF members a few days later. The HTTP working group was chartered to assist the QUIC working group during the design of HTTP/3, then assume responsibility for maintenance after publication. Support for HTTP/3 was added to Chrome (Canary build) in September 2019 and then eventually reached stable builds, but
HTTP/3 - Misplaced Pages Continue
2016-460: Was added to Cloudflare and Google Chrome first, and is also enabled in Firefox . HTTP/3 has lower latency for real-world web pages, if enabled on the server, and loads faster than with HTTP/2, in some cases over three times faster than HTTP/1.1 (which is still commonly only enabled). HTTP functions as a request–response protocol in the client–server model . A web browser , for example, may be
2064-450: Was already used by many web browsers and web servers. In early 1996 developers started to even include unofficial extensions of the HTTP/1.0 protocol (i.e. keep-alive connections, etc.) into their products by using drafts of the upcoming HTTP/1.1 specifications. Since early 1996, major web browsers and web server developers also started to implement new features specified by pre-standard HTTP/1.1 drafts specifications. End-user adoption of
2112-459: Was coined by Ted Nelson in 1965 in the Xanadu Project , which was in turn inspired by Vannevar Bush 's 1930s vision of the microfilm-based information retrieval and management " memex " system described in his 1945 essay " As We May Think ". Tim Berners-Lee and his team at CERN are credited with inventing the original HTTP, along with HTML and the associated technology for a web server and
2160-482: Was constituted with the aim to standardize and expand the protocol with extended operations, extended negotiation, richer meta-information, tied with a security protocol which became more efficient by adding additional methods and header fields . The HTTP WG planned to revise and publish new versions of the protocol as HTTP/1.0 and HTTP/1.1 within 1995, but, because of the many revisions, that timeline lasted much more than one year. The HTTP WG planned also to specify
2208-639: Was disabled by a feature flag. It was enabled by default in April 2020. Firefox added support for HTTP/3 in November 2019 through a feature flag and started enabling it by default in April 2021 in Firefox 88. Experimental support for HTTP/3 was added to Safari Technology Preview on April 8, 2020 and was included with Safari 14 that ships with iOS 14 and macOS 11 , but it's still disabled by default as of Safari 16, on both macOS and iOS. On 6 June 2022, IETF published HTTP/3 as
2256-433: Was released to include all improvements and updates based on previous (obsolete) HTTP/1.1 specifications. Resuming the old 1995 plan of previous HTTP Working Group, in 1997 an HTTP-NG Working Group was formed to develop a new HTTP protocol named HTTP-NG (HTTP New Generation). A few proposals / drafts were produced for the new protocol to use multiplexing of HTTP transactions inside a single TCP/IP connection, but in 1999,
2304-463: Was to greatly speed up web traffic (specially between future web browsers and its servers). SPDY was indeed much faster than HTTP/1.1 in many tests and so it was quickly adopted by Chromium and then by other major web browsers. Some of the ideas about multiplexing HTTP streams over a single TCP/IP connection were taken from various sources, including the work of W3C HTTP-NG Working Group. In January–March 2012, HTTP Working Group (HTTPbis) announced
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