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]
