cc_cubic —
CUBIC
Congestion Control Algorithm
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.
There are currently no tunable MIB variables.
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.
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.
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/
The
cc_cubic congestion control module and this
manual page were written by
Lawrence
Stewart
<
[email protected]>
and
David Hayes
<
[email protected]>.