xref: /freebsd/share/man/man4/cc_cubic.4 (revision 058ac3e8063366dafa634d9107642e12b038bf09)
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2.\" Copyright (c) 2009 Lawrence Stewart <lstewart@FreeBSD.org>
3.\" Copyright (c) 2010-2011 The FreeBSD Foundation
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6.\" Portions of this documentation were written at the Centre for Advanced
7.\" Internet Architectures, Swinburne University of Technology, Melbourne,
8.\" Australia by David Hayes under sponsorship from the FreeBSD Foundation.
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31.\" $FreeBSD$
32.\"
33.Dd September 13, 2022
34.Dt CC_CUBIC 4
35.Os
36.Sh NAME
37.Nm cc_cubic
38.Nd CUBIC Congestion Control Algorithm
39.Sh DESCRIPTION
40The CUBIC congestion control algorithm was designed to provide increased
41throughput in fast and long-distance networks.
42The CUBIC congestion control algorithm is the default for TCP.
43It attempts to maintain fairness when competing with legacy NewReno TCP in lower
44speed scenarios where NewReno is able to operate adequately.
45.Pp
46The congestion window is increased as a function of the time elapsed since the
47last congestion event.
48During regular operation, the window increase function follows a cubic function,
49with the inflection point set to be the congestion window value reached at the
50last congestion event.
51CUBIC also calculates an estimate of the congestion window that NewReno would
52have achieved at a given time after a congestion event.
53When updating the congestion window, the algorithm will choose the larger of the
54calculated CUBIC and estimated NewReno windows.
55.Pp
56CUBIC also backs off less on congestion by changing the multiplicative decrease
57factor from 1/2 (used by standard NewReno TCP) to 4/5.
58.Pp
59The implementation was done in a clean-room fashion, and is based on the
60Internet Draft and paper referenced in the
61.Sx SEE ALSO
62section below.
63.Sh MIB Variables
64There are currently no tunable MIB variables.
65.Sh SEE ALSO
66.Xr cc_cdg 4 ,
67.Xr cc_chd 4 ,
68.Xr cc_dctcp 4 ,
69.Xr cc_hd 4 ,
70.Xr cc_htcp 4 ,
71.Xr cc_newreno 4 ,
72.Xr cc_vegas 4 ,
73.Xr mod_cc 4 ,
74.Xr tcp 4 ,
75.Xr mod_cc 9
76.Rs
77.%A "Sangtae Ha"
78.%A "Injong Rhee"
79.%A "Lisong Xu"
80.%T "CUBIC for Fast Long-Distance Networks"
81.%U "https://tools.ietf.org/id/draft-rhee-tcpm-cubic-02.txt"
82.Re
83.Rs
84.%A "Sangtae Ha"
85.%A "Injong Rhee"
86.%A "Lisong Xu"
87.%T "CUBIC: a new TCP-friendly high-speed TCP variant"
88.%J "SIGOPS Oper. Syst. Rev."
89.%V "42"
90.%N "5"
91.%D "July 2008"
92.%P "64-74"
93.Re
94.Sh ACKNOWLEDGEMENTS
95Development and testing of this software were made possible in part by grants
96from the FreeBSD Foundation and Cisco University Research Program Fund at
97Community Foundation Silicon Valley.
98.Sh HISTORY
99The
100.Nm
101congestion control module first appeared in
102.Fx 9.0 .
103.Pp
104The module was first released in 2009 by Lawrence Stewart whilst studying at
105Swinburne University of Technology's Centre for Advanced Internet Architectures,
106Melbourne, Australia.
107More details are available at:
108.Pp
109http://caia.swin.edu.au/urp/newtcp/
110.Sh AUTHORS
111.An -nosplit
112The
113.Nm
114congestion control module and this manual page were written by
115.An Lawrence Stewart Aq Mt lstewart@FreeBSD.org
116and
117.An David Hayes Aq Mt david.hayes@ieee.org .
118