cc(4)		       FreeBSD Kernel Interfaces Manual 		 cc(4)

NAME

     cc -- Modular congestion control

DESCRIPTION

     The modular congestion control framework allows the TCP implementation to
     dynamically change the congestion control algorithm used by new and
     existing connections.  Algorithms are identified by a unique ascii(7)
     name.  Algorithm modules can be compiled into the kernel or loaded as
     kernel modules using the kld(4) facility.

     The default algorithm is NewReno, and all connections use the default
     unless explicitly overridden using the TCP_CONGESTION socket option (see
     tcp(4) for details).  The default can be changed using a sysctl(3) MIB
     variable detailed in the MIB Variables section below.

MIB Variables

     The framework exposes the following variables in the net.inet.tcp.cc
     branch of the sysctl(3) MIB:

     available	Read-only list of currently available congestion control algo-
		rithms by name.

     algorithm	Returns the current default congestion control algorithm when
		read, and changes the default when set.  When attempting to
		change the default algorithm, this variable should be set to
		one of the names listed by the net.inet.tcp.cc.available MIB
		variable.

SEE ALSO

     cc_chd(4), cc_cubic(4), cc_hd(4), cc_htcp(4), cc_newreno(4), cc_vegas(4),
     tcp(4), cc(9)

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 modular congestion control framework first appeared in
     FreeBSD 9.0.

     The framework was first released in 2007 by James Healy and Lawrence
     Stewart whilst working on the NewTCP research project at Swinburne Uni-
     versity of Technology's Centre for Advanced Internet Architectures, Mel-
     bourne, Australia, which was made possible in part by a grant from the
     Cisco University Research Program Fund at Community Foundation Silicon
     Valley.  More details are available at:

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

AUTHORS

     The cc facility was written by Lawrence Stewart <lstewart@FreeBSD.org>,
     James Healy <jimmy@deefa.com> and David Hayes <david.hayes@ieee.org>.

     This manual page was written by David Hayes <david.hayes@ieee.org> and
     Lawrence Stewart <lstewart@FreeBSD.org>.

FreeBSD 9.0		       February 15, 2011		   FreeBSD 9.0