Copyright (c) 2009 Lawrence Stewart <lstewart@FreeBSD.org> 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. Redistri...
NAMEcc_cubic - CUBIC Congestion Control Algorithm
DESCRIPTIONThe 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 Sx SEE ALSO section below.
MIB VariablesThere are currently no tunable MIB variables.
SEE ALSOcc_chd4, cc_hd4, cc_htcp4, cc_newreno4, cc_vegas4, mod_cc4, tcp(4), mod_cc9
- "Sangtae Ha" "Injong Rhee" "Lisong Xu" "CUBIC for Fast Long-Distance Networks"
- "Sangtae Ha" "Injong Rhee" "Lisong Xu" "CUBIC: a new TCP-friendly high-speed TCP variant" "SIGOPS Oper. Syst. Rev." "42" "5" "July 2008" "64-74"
ACKNOWLEDGEMENTSDevelopment 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.
HISTORYThe sysctl Cm net.inet.tcp.syncookies congestion control module first appeared in Fx 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: