Micro Transport Protocol: Difference between revisions

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{{Short description|An open UDP-based variant of the BitTorrent peerPeer-to-peer file -sharing protocol}}

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'''Micro Transport Protocol''' or ('''μTP''', (sometimes also '''uTP''') is an [[open standard|open]] [[User Datagram Protocol|UDP]]-based (UDP-based) variant of the [[BitTorrent]] [[peer-to-peer file sharing|peer-to-peer file-sharing]] [[Protocolprotocol (computing)|protocol]] intended to mitigate poor [[network latency|latency]] and other [[network congestion#Congestion control|congestion control]] problems found in conventional BitTorrent over [[Transmission Control Protocol|TCP]] (TCP), while providing reliable, ordered delivery.

It was devised to automatically slow down<ref>{{cite web|url=http://forum.bittorrent.org/viewtopic.php?pid%3D762#p762 |title=ArchivedForum.bittorrent.org copy/ A few comments about µTP (BEP-29) |access-date=November 15, 2009 |url-status=dead|archive-url=https://web.archive.org/web/20100301125306/http://forum.bittorrent.org/viewtopic.php?pid=762 |archive-date=March 1, 2010 }}</ref> the rate at which packets of data are transmitted between users of [[peer-to-peer]] file -sharing [[BitTorrent|torrent]]s when it interferes with other applications. For example, the protocol should automatically allow the sharing of ana [[Digital subscriber line|DSL line]] between a BitTorrent application and a web browser.

==Development==

μTP emerged from research at [[Internet2]] on [[Quality of service|QoS]] and high-performance [[bulk transport]], was adapted for use as a background transport protocol by Plicto, founded by [[Stanislav Shalunov]] and Ben Teitelbaum<ref>[http://www.fastcolabs.com/3014951/why-your-bittorrent-downloads-move-so-fast This Is How Your BitTorrent Downloads Move So Fast], Fastcolabs, 2013-07-29, Retrieved November 6, 2013</ref> and later acquired by [[BitTorrent (company)|BitTorrent, Inc.]] in 2006, and further developed within its new owner.<ref>http://www.slideshare.net/eCommConf/eric-klinker-presentation-at-emerging-communication-conference-awards-2010-america/11 uTP timeline, slide 11, "This Green Revolution-improving the yield of your network investment", eComm America Conference, San Francisco, CA, April 2010.</ref> It was first introduced in the μTorrent 1.8.x beta branches, and publicized in the alpha builds of [[μTorrent]] 1.9.<ref>{{Cite web|last=Beijnum|first=Iljitsch van|date=2008-12-02|title=?Torrent's switch to UDP and why the sky isn't falling|url=https://arstechnica.com/uncategorized/2008/12/utorrents-switch-to-udp-and-why-the-sky-isnt-falling/|access-date=2021-05-11|website=Ars Technica|language=en-us}}</ref><ref>{{Cite web|title=uTorrent shifts towards UDP to make it work better|url=https://www.thinkbroadband.com/news/3807-utorrent-shifts-towards-udp-to-make-it-work-better|url-status=live|access-date=2021-05-11|website=www.thinkbroadband.com|date=3 December 2008 }}</ref>

The implementation of μTP used in μTorrent was later separated into the "libutp" library and published under the [[MIT license]].<ref>{{cite web |url=http://forum.utorrent.com/viewtopic.php?id=76640 |title=ArchivedLibutp, copyan open source implementation of µTP, has now been released (Page 1) / Announcements / µTorrent Community Forums |access-date=2011-01-15 |url-status=dead|archive-url=https://web.archive.org/web/20110123183649/http://forum.utorrent.com/viewtopic.php?id=76640 |archive-date=2011-01-23 }}</ref><ref>{{Citation|title=bittorrent/libutp|date=2021-05-08|url=https://github.com/bittorrent/libutp|publisher=BitTorrent Inc.|access-date=2021-05-11}}</ref>

The first [[free software]] client to implement μTP was [[KTorrent]] 4.0.<ref>{{Cite web|title=KTorrent First BitTorrent Client To Adopt Open Source uTP * TorrentFreak|url=https://torrentfreak.com/ktorrent-first-bittorrent-client-to-adopt-open-source-utp-100528/|access-date=2021-05-11|language=en}}</ref><ref>{{Cite web|date=24 May 2010|title=KTorrent 4.0 is out|url=http://ktorrent.pwsp.net/?q=node%2F42|url-status=live|archive-url=https://web.archive.org/web/20150402090740/http://ktorrent.pwsp.net/?q=node%2F42|archive-date=2015-04-02}}</ref> [[libtorrent]] implements μTP since version 0.16.0<ref>{{Cite web|title=Google Code Archive - Long-term storage for Google Code Project Hosting.|url=https://code.google.com/archive/p/libtorrent/downloads|access-date=2021-05-11|website=code.google.com}}</ref> and it is used in [[qBittorrent]] since 2.8.0.<ref>{{Cite web|title=qBittorrent Official Website|url=https://www.qbittorrent.org/news.php|access-date=2021-05-11|website=www.qbittorrent.org}}</ref> [[Tixati]] implements μTP since version 1.72.<ref>{{Cite web|title=Tixati.com - News|url=https://www.tixati.com/news/|access-date=2021-05-11|website=www.tixati.com}}</ref> [[Vuze]] (formerly Azureus) implements μTP since version 4.6.0.0.<ref>{{Cite web|title=Version 4400 4702 Changelog - VuzeWiki|url=https://wiki.vuze.com/w/Version_4400_4702_Changelog|access-date=2021-05-11|website=wiki.vuze.com}}</ref> [[Transmission (BitTorrent client)|Transmission]] implements μTP since version 2.30.<ref>{{Cite web |url=https://trac.transmissionbt.com/wiki/Changes#version-2.30 |title=ArchivedChanges copy– Transmission |access-date=2012-07-12 |archive-url=https://web.archive.org/web/20150524013026/https://trac.transmissionbt.com/wiki/Changes#version-2.30 |archive-date=2015-05-24 |url-status=dead }}</ref>

==μTP congestion control==

The congestion control algorithm used by μTP, known as Low Extra Delay Background Transport ([[LEDBAT]]), aims to decrease the latency caused by applications using the protocol while maximizing bandwidth when latency is not excessive.<ref>{{Cite web |url=http://searchnetworking.techtarget.com.au/articles/27957-Torrents-of-Disruption-on-the-Way- |title=Technical information about UDP |access-date=2008-12-23 |archive-url=https://web.archive.org/web/20090512123108/http://searchnetworking.techtarget.com.au/articles/27957-Torrents-of-Disruption-on-the-Way- |archive-date=2009-05-12 |url-status=dead }}</ref><ref>{{cite web|url=http://forum.bittorrent.org/viewtopic.php?pid%3D762#p762 |title=ArchivedForum.bittorrent.org copy/ A few comments about µTP (BEP-29) |access-date=November 15, 2009 |url-status=dead|archive-url=https://web.archive.org/web/20100301125306/http://forum.bittorrent.org/viewtopic.php?pid=762 |archive-date=March 1, 2010 }}</ref> Additionally, information from the μTP congestion controller can be used to choose the transfer rate of TCP connections.<ref>{{cite web|url=http://forum.utorrent.com/viewtopic.php?pid=377209#p377209 |date=2008-11-26 |title=Post by developer "Greg Hazel" in thread "μTorrent 1.9 alpha" |access-date=2009-03-08 |url-status=dead|archive-url=https://web.archive.org/web/20090208093326/http://forum.utorrent.com/viewtopic.php?pid=377209 |archive-date=February 8, 2009 }}</ref>

{{Internet|expanded=Protocols}}

LEDBAT is described in {{IETF RFC|6817}}. As of 2009, the details of the μTP implementation were different from those of the then-current Internet Draft.<ref>{{cite web|url=http://forum.bittorrent.org/viewtopic.php?pid%3D753#p753 |title=ArchivedForum.bittorrent.org copy/ A few comments about µTP (BEP-29) |access-date=November 15, 2009 |url-status=dead|archive-url=https://web.archive.org/web/20110725080523/http://forum.bittorrent.org/viewtopic.php?pid=753 |archive-date=July 25, 2011 }}{{Full citation needed|date=December 2014}}</ref>

μTP also adds support for [[NAT traversal]] using [[UDP hole punching]] between two port-restricted peers where a third unrestricted peer acts as a [[STUN]] server.<ref>{{cite web|url=http://forum.utorrent.com/viewtopic.php?id%3D49813 |title=ArchivedΜTorrent copy1.9 alpha 15380 (Page 1) / Announcements / µTorrent Community Forums |access-date=December 23, 2012 |url-status=dead|archive-url=https://web.archive.org/web/20130325195455/http://forum.utorrent.com/viewtopic.php?id=49813 |archive-date=March 25, 2013 }}</ref><ref>{{cite web|url=http://forum.utorrent.com/viewtopic.php?pid%3D407732#p407732 |title=ArchivedDistributed UDP hole punching for the BitTorrent protocol (Page 1) / Protocol Design Discussion / µTorrent Community copyForums |access-date=December 23, 2012 |url-status=dead|archive-url=https://web.archive.org/web/20130619125216/http://forum.utorrent.com/viewtopic.php?pid=407732 |archive-date=June 19, 2013 }}</ref>

==See also==

* [[TCP congestion control]]

* [[Multipurpose Transaction Protocol]] (MTP)

* [[QUIC]] (Quick UDP Internet Connections)

* [[Real-Time Media Flow Protocol]] (RTMFP)

* [[Stream Control Transmission Protocol]] (SCTP UDP Encapsulation; {{IETF RFC|6951}})

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== External links ==

* [http://bittorrent.org/beps/bep_0029.html BitTorrent Enhancement Proposal 29] - μTorrent transport protocol

* [httphttps://wwwusers.ececs.ricenorthwestern.edu/networks~akuzma/rice/TCP-LP/ TCP-LP Low Priority]

* [https://archive.today/20130415085006/http://libswift.org/ swift - the multiparty transport protocol]

{{BitTorrent}}