.\" .\" Copyright (c) 2009 Lawrence Stewart .\" Copyright (c) 2010-2011 The FreeBSD Foundation .\" All rights reserved. .\" .\" Portions of this documentation were written at the Centre for Advanced .\" Internet Architectures, Swinburne University of Technology, Melbourne, .\" Australia by David Hayes under sponsorship from the FreeBSD Foundation. .\" .\" Redistribution and use in source and binary forms, with or without .\" modification, are permitted provided that the following conditions .\" are met: .\" 1. Redistributions of source code must retain the above copyright .\" notice, this list of conditions and the following disclaimer. .\" 2. Redistributions in binary form must reproduce the above copyright .\" notice, this list of conditions and the following disclaimer in the .\" documentation and/or other materials provided with the distribution. .\" .\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND .\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE .\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE .\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE FOR .\" ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL .\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS .\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) .\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT .\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF .\" SUCH DAMAGE. .\" .\" $FreeBSD: releng/12.2/share/man/man4/cc_cubic.4 267938 2014-06-26 21:46:14Z bapt $ .\" .Dd September 15, 2011 .Dt CC_CUBIC 4 .Os .Sh NAME .Nm cc_cubic .Nd CUBIC Congestion Control Algorithm .Sh DESCRIPTION The CUBIC congestion control algorithm was designed to provide increased throughput in fast and long-distance networks. It attempts to maintain fairness when competing with legacy NewReno TCP in lower speed scenarios where NewReno is able to operate adequately. .Pp The congestion window is increased as a function of the time elapsed since the last congestion event. During regular operation, the window increase function follows a cubic function, with the inflection point set to be the congestion window value reached at the last congestion event. CUBIC also calculates an estimate of the congestion window that NewReno would have achieved at a given time after a congestion event. When updating the congestion window, the algorithm will choose the larger of the calculated CUBIC and estimated NewReno windows. .Pp CUBIC also backs off less on congestion by changing the multiplicative decrease factor from 1/2 (used by standard NewReno TCP) to 4/5. .Pp The implementation was done in a clean-room fashion, and is based on the Internet Draft and paper referenced in the .Sx SEE ALSO section below. .Sh MIB Variables There are currently no tunable MIB variables. .Sh SEE ALSO .Xr cc_chd 4 , .Xr cc_hd 4 , .Xr cc_htcp 4 , .Xr cc_newreno 4 , .Xr cc_vegas 4 , .Xr mod_cc 4 , .Xr tcp 4 , .Xr mod_cc 9 .Rs .%A "Sangtae Ha" .%A "Injong Rhee" .%A "Lisong Xu" .%T "CUBIC for Fast Long-Distance Networks" .%U "http://tools.ietf.org/id/draft-rhee-tcpm-cubic-02.txt" .Re .Rs .%A "Sangtae Ha" .%A "Injong Rhee" .%A "Lisong Xu" .%T "CUBIC: a new TCP-friendly high-speed TCP variant" .%J "SIGOPS Oper. Syst. Rev." .%V "42" .%N "5" .%D "July 2008" .%P "64-74" .Re .Sh ACKNOWLEDGEMENTS Development and testing of this software were made possible in part by grants from the FreeBSD Foundation and Cisco University Research Program Fund at Community Foundation Silicon Valley. .Sh HISTORY The .Nm congestion control module first appeared in .Fx 9.0 . .Pp The module was first released in 2009 by Lawrence Stewart whilst studying at Swinburne University of Technology's Centre for Advanced Internet Architectures, Melbourne, Australia. More details are available at: .Pp http://caia.swin.edu.au/urp/newtcp/ .Sh AUTHORS .An -nosplit The .Nm congestion control module and this manual page were written by .An Lawrence Stewart Aq Mt lstewart@FreeBSD.org and .An David Hayes Aq Mt david.hayes@ieee.org .