8ad8794452
DCTCP congestion control algorithm aims to maximise throughput and minimise latency in data center networks by utilising the proportion of Explicit Congestion Notification (ECN) marked packets received from capable hardware as a congestion signal. Highlights: Implemented as a mod_cc(4) module. ECN (Explicit congestion notification) processing is done differently from RFC3168. Takes one-sided DCTCP into consideration where only one of the sides is using DCTCP and other is using standard ECN. IETF draft: http://tools.ietf.org/html/draft-bensley-tcpm-dctcp-00 Thesis report by Midori Kato: https://eggert.org/students/kato-thesis.pdf Submitted by: Midori Kato <katoon@sfc.wide.ad.jp> and Lars Eggert <lars@netapp.com> with help and modifications from hiren Differential Revision: https://reviews.freebsd.org/D604 Reviewed by: gnn
120 lines
4.0 KiB
Groff
120 lines
4.0 KiB
Groff
.\"
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.\" Copyright (c) 2010-2011 The FreeBSD Foundation
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.\" All rights reserved.
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.\"
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.\" This documentation was written at the Centre for Advanced Internet
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.\" Architectures, Swinburne University of Technology, Melbourne, Australia by
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.\" David Hayes and Lawrence Stewart under sponsorship from the FreeBSD
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.\" Foundation.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE FOR
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.\" ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\" $FreeBSD$
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.\"
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.Dd January 12, 2015
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.Dt MOD_CC 4
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.Os
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.Sh NAME
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.Nm mod_cc
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.Nd Modular congestion control
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.Sh DESCRIPTION
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The modular congestion control framework allows the TCP implementation to
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dynamically change the congestion control algorithm used by new and existing
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connections.
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Algorithms are identified by a unique
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.Xr ascii 7
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name.
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Algorithm modules can be compiled into the kernel or loaded as kernel modules
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using the
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.Xr kld 4
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facility.
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.Pp
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The default algorithm is NewReno, and all connections use the default unless
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explicitly overridden using the TCP_CONGESTION socket option (see
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.Xr tcp 4
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for details).
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The default can be changed using a
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.Xr sysctl 3
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MIB variable detailed in the
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.Sx MIB Variables
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section below.
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.Sh MIB Variables
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The framework exposes the following variables in the
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.Va net.inet.tcp.cc
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branch of the
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.Xr sysctl 3
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MIB:
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.Bl -tag -width ".Va available"
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.It Va available
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Read-only list of currently available congestion control algorithms by name.
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.It Va algorithm
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Returns the current default congestion control algorithm when read, and changes
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the default when set.
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When attempting to change the default algorithm, this variable should be set to
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one of the names listed by the
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.Va net.inet.tcp.cc.available
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MIB variable.
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.El
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.Sh SEE ALSO
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.Xr cc_cdg 4 ,
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.Xr cc_chd 4 ,
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.Xr cc_cubic 4 ,
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.Xr cc_dctcp 4 ,
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.Xr cc_hd 4 ,
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.Xr cc_htcp 4 ,
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.Xr cc_newreno 4 ,
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.Xr cc_vegas 4 ,
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.Xr tcp 4 ,
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.Xr mod_cc 9
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.Sh ACKNOWLEDGEMENTS
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Development and testing of this software were made possible in part by grants
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from the FreeBSD Foundation and Cisco University Research Program Fund at
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Community Foundation Silicon Valley.
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.Sh HISTORY
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The
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.Nm
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modular congestion control framework first appeared in
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.Fx 9.0 .
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.Pp
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The framework was first released in 2007 by James Healy and Lawrence Stewart
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whilst working on the NewTCP research project at Swinburne University of
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Technology's Centre for Advanced Internet Architectures, Melbourne, Australia,
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which was made possible in part by a grant from the Cisco University Research
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Program Fund at Community Foundation Silicon Valley.
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More details are available at:
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.Pp
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http://caia.swin.edu.au/urp/newtcp/
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.Sh AUTHORS
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.An -nosplit
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The
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.Nm
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facility was written by
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.An Lawrence Stewart Aq Mt lstewart@FreeBSD.org ,
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.An James Healy Aq Mt jimmy@deefa.com
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and
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.An David Hayes Aq Mt david.hayes@ieee.org .
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.Pp
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This manual page was written by
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.An David Hayes Aq Mt david.hayes@ieee.org
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and
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.An Lawrence Stewart Aq Mt lstewart@FreeBSD.org .
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