2 .\" Copyright (c) 2009 Lawrence Stewart <lstewart@FreeBSD.org>
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38 .Nd CUBIC Congestion Control Algorithm
40 The CUBIC congestion control algorithm was designed to provide increased
41 throughput in fast and long-distance networks.
42 The CUBIC congestion control algorithm is the default for TCP.
43 It attempts to maintain fairness when competing with legacy NewReno TCP in lower
44 speed scenarios where NewReno is able to operate adequately.
46 The congestion window is increased as a function of the time elapsed since the
47 last congestion event.
48 During regular operation, the window increase function follows a cubic function,
49 with the inflection point set to be the congestion window value reached at the
50 last congestion event.
51 CUBIC also calculates an estimate of the congestion window that NewReno would
52 have achieved at a given time after a congestion event.
53 When updating the congestion window, the algorithm will choose the larger of the
54 calculated CUBIC and estimated NewReno windows.
56 CUBIC also backs off less on congestion by changing the multiplicative decrease
57 factor from 1/2 (used by standard NewReno TCP) to 4/5.
59 The implementation was done in a clean-room fashion, and is based on the
60 Internet Draft and paper referenced in the
64 There are currently no tunable MIB variables.
80 .%T "CUBIC for Fast Long-Distance Networks"
81 .%U "https://tools.ietf.org/id/draft-rhee-tcpm-cubic-02.txt"
87 .%T "CUBIC: a new TCP-friendly high-speed TCP variant"
88 .%J "SIGOPS Oper. Syst. Rev."
95 Development and testing of this software were made possible in part by grants
96 from the FreeBSD Foundation and Cisco University Research Program Fund at
97 Community Foundation Silicon Valley.
101 congestion control module first appeared in
104 This became the default congestion algorithm for FreeBSD in version
109 The module was first released in 2009 by Lawrence Stewart whilst studying at
110 Swinburne University of Technology's Centre for Advanced Internet Architectures,
111 Melbourne, Australia.
112 More details are available at:
114 http://caia.swin.edu.au/urp/newtcp/
119 congestion control module and this manual page were written by
120 .An Lawrence Stewart Aq Mt lstewart@FreeBSD.org
122 .An David Hayes Aq Mt david.hayes@ieee.org .