SPDY

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SPDY (pronounced "speedy") [1] is an obsolete open-specification communication protocol developed for transporting web content. [1] SPDY became the basis for HTTP/2 specification. However, HTTP/2 diverged from SPDY and eventually HTTP/2 subsumed all usecases of SPDY. [2] After HTTP/2 was ratified as a standard, major implementers, including Google, Mozilla, and Apple, deprecated SPDY in favor of HTTP/2. Since 2021, no modern browser supports SPDY.

Contents

Google announced SPDY in late 2009 and deployed in 2010. SPDY manipulates HTTP traffic, with particular goals of reducing web page load latency and improving web security. SPDY achieves reduced latency through compression, multiplexing, and prioritization, [1] although this depends on a combination of network and website deployment conditions. [3] [4] [5] The name "SPDY" is not an acronym. [6]

History

HTTP/2 was first discussed when it became apparent that SPDY was gaining traction with implementers (like Mozilla and nginx), and was showing significant improvements over HTTP/1.x. After a call for proposals and a selection process, SPDY was chosen as the basis for HTTP/2. Since then, there have been a number of changes, based on discussion in the Working Group and feedback from implementers. [2]

As of July 2012, the group developing SPDY stated publicly that it was working toward standardisation (available as an Internet Draft). [7] The first draft of HTTP/2 used SPDY as the working base for its specification draft and editing. [8] The IETF working group for HTTPbis has released the draft of HTTP/2. [9] SPDY (draft-mbelshe-httpbis-spdy-00) was chosen as the starting point. [10] [11]

Throughout the process, the core developers of SPDY have been involved in the development of HTTP/2, including both Mike Belshe and Roberto Peon.

Chromium, [12] Mozilla Firefox, [13] Opera, [14] Amazon Silk, Internet Explorer, [15] and Safari [16] expressed support for SPDY at the time.

In February 2015, Google announced that following ratification of the HTTP/2 standard, support for SPDY would be deprecated, and that support for SPDY would be withdrawn. [17] On May 15, 2015, HTTP/2 was officially ratified as RFC   7540.

On February 11, 2016, Google announced that Chrome would no longer support SPDY after May 15, 2016, the one-year anniversary of RFC   7540 which standardized HTTP/2. [18]

On January 25, 2019, Apple announced that SPDY would be deprecated in favor of HTTP/2, and would be removed in future releases. [19]

Google removed SPDY support in Google Chrome 51 which was released in 2016. [20] Mozilla removed it in Firefox 50. [21] Apple has deprecated the technology in macOS 10.14.4 and iOS 12.2. [19]

Protocol versions

SPDY is a versioned protocol. SPDY control frames contain 15 dedicated bits to indicate the version of protocol used for the current session. [22]

Design

The goal of SPDY is to reduce web page load time. [35] This is achieved by prioritizing and multiplexing the transfer of web page subresources so that only one connection per client is required. [1] [36] TLS encryption is nearly ubiquitous in SPDY implementations, and transmission headers are gzip- or DEFLATE-compressed by design [27] (in contrast to HTTP, where the headers are sent as human-readable text). Moreover, servers may hint or even push content instead of awaiting individual requests for each resource of a web page. [37]

SPDY requires the use of SSL/TLS (with TLS extension ALPN) for security but it also supports operation over plain TCP. The requirement for SSL is for security and to avoid incompatibility when communication is across a proxy.

Relation to HTTP

SPDY does not replace HTTP; it modifies the way HTTP requests and responses are sent over the wire. [1] This means that all existing server-side applications can be used without modification if a SPDY-compatible translation layer is put in place.

SPDY is effectively a tunnel for the HTTP and HTTPS protocols. When sent over SPDY, HTTP requests are processed, tokenized, simplified and compressed. For example, each SPDY endpoint keeps track of which headers have been sent in past requests and can avoid resending the headers that have not changed; those that must be sent are compressed.

Protocol support

For use within HTTPS, SPDY requires the TLS extension Next Protocol Negotiation (NPN) [38] or Application-Layer Protocol Negotiation (ALPN) [39] thus browser and server support depends on the HTTPS library.

OpenSSL 1.0.1 or greater introduces NPN. [40] Patches to add NPN support have also been written for NSS and TLSLite. [41]

Security Support Provider Interface (SSPI) from Microsoft have not implemented the NPN extension to its TLS implementation. This has prevented SPDY inclusion in the latest .NET Framework versions. Since SPDY specification is being refined and HTTP/2 is expected to include SPDY implementation one could expect Microsoft to release support after HTTP/2 is finalized.

Client (browser) support and usage

Server support and usage

As of May 2021, approximately 0.1% of all websites support SPDY, [56] in part due to transition to HTTP/2. In 2016, NGINX and Apache [57] were the major providers of SPDY traffic. [58] In 2015, NGINX 1.9.5 dropped SPDY support in favor of HTTP/2. [59]

Some Google services (e.g. Google Search, Gmail, and other SSL-enabled services) use SPDY when available. [60] Google's ads are also served from SPDY-enabled servers. [61]

A brief history of SPDY support amongst major web players:

According to W3Techs, as of May 2021, most SPDY-enabled websites use nginx, with the LiteSpeed web server coming second. [58]

See also

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References

  1. 1 2 3 4 5 "SPDY: An experimental protocol for a faster web". Chromium Developer Documentation. Retrieved 2009-11-13.
  2. 1 2 "HTTP/2 Frequently Asked Questions". http2.github.io.
  3. ↑ Elkhatib, Yehia; Tyson, Gareth; Welzl, Michael (2014). 2014 IFIP Networking Conference. pp. 1–9. CiteSeerX   10.1.1.698.2343 . doi:10.1109/IFIPNetworking.2014.6857089. ISBN   978-3-901882-58-6. S2CID   13841087.
  4. ↑ Podjarny, Guy. "Not as SPDY as You Thought". Archived from the original on 12 October 2012. Retrieved 12 October 2012.
  5. ↑ Abdelsalam, Ahmed; Celandroni, Nedo; Collina, Matteo; Cruickshank, Haitham; Fairhurst, Gorry; Ferro, Erina; Gotta, Alberto; Luglio, Michele; Roseti, Cesare (2015-07-01). "A deep analysis on future web technologies and protocols over broadband GEO satellite networks". International Journal of Satellite Communications and Networking. 33 (5): 451–472. doi:10.1002/sat.1120. ISSN   1542-0981.
  6. ↑ "SPDY frequently asked questions". The Chromium Projects. Retrieved 2015-02-23. We wanted a name that captures speed. SPDY, pronounced "SPeeDY", captures this and also shows how compression can help improve speed.
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  11. ↑ "HTTPbis Working Group Start To Consider HTTP/2.0". InfoQ. 2012-04-28. Retrieved 2012-08-09.
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  13. 1 2 "Mozilla Bug 528288 - Implement SPDY protocol".
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  19. 1 2 Marshall, Scott (2019-01-25). "Removing Legacy SPDY Protocol Support". WebKit. Retrieved 2019-03-07.
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  22. 1 2 SPDY Protocol - Draft 2: "Currently, the only valid string is "spdy/2" (spdy/1 isn't implemented anywhere anymore)".
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  26. 1 2 3 OpenLiteSpeed 1.1 (With SPDY!) Retrieved 2013-08-12.
  27. 1 2 "SPDY Protocol — Draft 3" . Retrieved 25 August 2012.
  28. 1 2 "Firefox 15 — Release Notes" . Retrieved 3 September 2012.
  29. ↑ "SPDY Protocol — Draft 3.1" . Retrieved 17 November 2013.
  30. 1 2 "Firefox Notes Desktop". 2014-02-04. Retrieved 2014-02-05.
  31. 1 2 OpenLiteSpeed 1st Web Server to Support SPDY/3.1! Retrieved 2014-1-10.
  32. ↑ NGINX Announces Support for SPDY/3.1 Retrieved 2014-02-04.
  33. ↑ F5 Bigip 11.6.0 Release Notes Retrieved 2015-03-10.
  34. ↑ "Upcoming SPDY/4 changes to bring it more in sync with the HTTP/2 draft" . Retrieved 27 February 2014.
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  36. ↑ Iljitsch van Beijnum (2009-11-12). "SPDY: Google wants to speed up the web by ditching HTTP". Ars Technica. Retrieved 2009-11-13.
  37. ↑ Mirko Lindner (13 November 2009). "Google stellt HTTP-Alternative SPDY vor" (in German). Retrieved 2011-10-21.
  38. ↑ NPN protocol and explanation about its need to tunnel SPDY over HTTPS.
  39. ↑ "ImperialViolet - NPN and ALPN". www.imperialviolet.org. Retrieved 2021-06-08.
  40. ↑ Openssl 1.0.1 changelog.
  41. ↑ TLS Next Protocol Negotiation. Section: Implementations Archived 2012-07-30 at the Wayback Machine .
  42. ↑ Chromium SPDY client implementation.
  43. ↑ Chromium: SPDY proxy examples Archived 2017-09-19 at the Wayback Machine .
  44. ↑ List of Chromium Command Line Switches.
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  48. ↑ David Honneffer, Documentation Specialist. "Opera: Opera 12.10 Changelog".
  49. ↑ "WebGL, SPDY/3, New Dev Tools, & More Confirmed For IE11 In Win 8.1". Microsoft News.
  50. ↑ "IE11 Changes". Microsoft.
  51. ↑ "Microsoft Releases Internet Explorer 11 for Windows 7". 2013-11-07.
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  57. ↑ "Usage of web servers for websites". w3techs.com. Retrieved 2016-07-26.
  58. 1 2 "Distribution of Web Servers among websites that use SPDY" . Retrieved 2021-05-04.
  59. 1 2 "HTTP/2 Supported in Open Source NGINX 1.9.5 - NGINX". 22 September 2015.
  60. ↑ spdy-dev mailing list: SPDY on Google servers?.
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  62. ↑ "Research Blog: A 2x Faster Web". Research Blog.
  63. ↑ Ido Safruti (2011-06-15). "From Fast to SPDY — Velocity 2011".
  64. ↑ "Google Groups".
  65. ↑ Twitter Adopts SPDY Archived 2012-03-11 at the Wayback Machine .
  66. ↑ Jetty Feature SPDY.
  67. ↑ "indutny/node-spdy · GitHub". Github.com. Retrieved 2012-05-10.
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  71. ↑ "@DeviaVir It's going well ;) So far we're on schedule, should hopefully be available by the end of May". Twitter.
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  76. ↑ Finley, Klint. "Facebook Makes Itself a Bit More SPDY". Wired. Retrieved 18 March 2013.
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  78. ↑ DSM 5.0 beta
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