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CC_CUBIC(4)	       FreeBSD Kernel Interfaces Manual		   CC_CUBIC(4)

NAME
     cc_cubic -- CUBIC Congestion Control Algorithm

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.

     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.

     CUBIC also	backs off less on congestion by	changing the multiplicative
     decrease factor from 1/2 (used by standard	NewReno	TCP) to	4/5.

     The implementation	was done in a clean-room fashion, and is based on the
     Internet Draft and	paper referenced in the	SEE ALSO section below.

MIB Variables
     There are currently no tunable MIB	variables.

SEE ALSO
     cc_chd(4),	cc_hd(4), cc_htcp(4), cc_newreno(4), cc_vegas(4), mod_cc(4),
     tcp(4), mod_cc(9)

     Sangtae Ha, Injong	Rhee, and Lisong Xu, CUBIC for Fast Long-Distance
     Networks, http://tools.ietf.org/id/draft-rhee-tcpm-cubic-02.txt.

     Sangtae Ha, Injong	Rhee, and Lisong Xu, "CUBIC: a new TCP-friendly	high-
     speed TCP variant", SIGOPS	Oper. Syst. Rev., 5, 42, 64-74,	July 2008.

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.

HISTORY
     The cc_cubic congestion control module first appeared in FreeBSD 9.0.

     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:

     http://caia.swin.edu.au/urp/newtcp/

AUTHORS
     The cc_cubic congestion control module and	this manual page were written
     by	Lawrence Stewart <lstewart@FreeBSD.org>	and David Hayes
     <david.hayes@ieee.org>.

FreeBSD	10.1		      September	15, 2011		  FreeBSD 10.1

NAME | DESCRIPTION | MIB Variables | SEE ALSO | ACKNOWLEDGEMENTS | HISTORY | AUTHORS

Want to link to this manual page? Use this URL:
<http://www.freebsd.org/cgi/man.cgi?query=cc_cubic&sektion=4&manpath=FreeBSD+9.0-RELEASE>

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