It was devised to automatically slow down[1] the rate at which packets of data are transmitted between users of
peer-to-peer file sharing
torrents when it interferes with other applications. For example, the protocol should automatically allow the sharing of a
DSL line between a BitTorrent application and a web browser.
Development
μTP emerged from research at
Internet2 on
QoS and high-performance
bulk transport, was adapted for use as a background transport protocol by Plicto, founded by
Stanislav Shalunov and Ben Teitelbaum[2] and later acquired by
BitTorrent, Inc. in 2006, and further developed within its new owner.[3] It was first introduced in the μTorrent 1.8.x beta branches, and publicized in the alpha builds of
μTorrent 1.9.[4][5]
The implementation of μTP used in μTorrent was later separated into the "libutp" library and published under the
MIT license.[6][7]
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.[15][16] Additionally, information from the μTP congestion controller can be used to choose the transfer rate of TCP connections.[17]