767964fd86
CUBIC replaced NEWRENO as the default congestion control algorithm inbb1d472d79. Update man pages to reflect that. Fixes:bb1d472d79Reviewed by: imp Pull Request: https://github.com/freebsd/freebsd-src/pull/641
177 lines
5.5 KiB
Groff
177 lines
5.5 KiB
Groff
.\"
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.\" Copyright (c) 2009 Lawrence Stewart <lstewart@FreeBSD.org>
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.\" Copyright (c) 2011 The FreeBSD Foundation
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.\" All rights reserved.
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.\"
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.\" Portions of this documentation were written at the Centre for Advanced
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.\" Internet Architectures, Swinburne University of Technology, Melbourne,
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.\" Australia by Lawrence Stewart under sponsorship from the FreeBSD 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 February 4, 2023
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.Dt CC_NEWRENO 4
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.Os
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.Sh NAME
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.Nm cc_newreno
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.Nd NewReno Congestion Control Algorithm
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.Sh SYNOPSIS
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.In netinet/cc/cc_newreno.h
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.Sh DESCRIPTION
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Details about the algorithm can be found in RFC5681.
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.Sh Socket Options
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The
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.Nm
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module supports a number of socket options under TCP_CCALGOOPT (refer to
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.Xr tcp 4
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and
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.Xr mod_cc 9 for details)
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which can
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be set with
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.Xr setsockopt 2
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and tested with
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.Xr getsockopt 2 .
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The
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.Nm
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socket options use this structure defined in
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<sys/netinet/cc/cc_newreno.h>:
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.Bd -literal
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struct cc_newreno_opts {
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int name;
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uint32_t val;
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}
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.Ed
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.Bl -tag -width ".Va CC_NEWRENO_BETA_ECN"
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.It Va CC_NEWRENO_BETA
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Multiplicative window decrease factor, specified as a percentage, applied to
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the congestion window in response to a congestion signal per: cwnd = (cwnd *
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CC_NEWRENO_BETA) / 100.
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Default is 50.
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.It Va CC_NEWRENO_BETA_ECN
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Multiplicative window decrease factor, specified as a percentage, applied to
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the congestion window in response to an ECN congestion signal when
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.Va net.inet.tcp.cc.abe=1
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per: cwnd = (cwnd * CC_NEWRENO_BETA_ECN) / 100.
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Default is 80.
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.Pp
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Note that currently the only way to enable
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hystart++ is to enable it via socket option.
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When enabling it a value of 1 will enable precise internet-draft (version 4) behavior
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(subject to any MIB variable settings), other setting (2 and 3) are experimental.
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.El
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.Pp
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Note that hystart++ requires the TCP stack be able to call to the congestion
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controller with both the
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.Va newround
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function as well as the
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.Va rttsample
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function.
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Currently the only TCP stacks that provide this feedback to the
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congestion controller is rack.
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.Sh MIB Variables
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The algorithm exposes these variables in the
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.Va net.inet.tcp.cc.newreno
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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 beta_ecn"
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.It Va beta
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Multiplicative window decrease factor, specified as a percentage, applied to
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the congestion window in response to a congestion signal per: cwnd = (cwnd *
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beta) / 100.
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Default is 50.
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.It Va beta_ecn
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Multiplicative window decrease factor, specified as a percentage, applied to
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the congestion window in response to an ECN congestion signal when
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.Va net.inet.tcp.cc.abe=1
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per: cwnd = (cwnd * beta_ecn) / 100.
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Default is 80.
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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_vegas 4 ,
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.Xr mod_cc 4 ,
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.Xr tcp 4 ,
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.Xr mod_cc 9
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.Rs
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.%A "Mark Allman"
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.%A "Vern Paxson"
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.%A "Ethan Blanton"
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.%T "TCP Congestion Control"
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.%O "RFC 5681"
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.Re
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.Rs
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.%A "Naeem Khademi"
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.%A "Michael Welzl"
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.%A "Grenville Armitage"
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.%A "Gorry Fairhurst"
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.%T "TCP Alternative Backoff with ECN (ABE)"
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.%O "RFC 8511"
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.Re
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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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congestion control algorithm first appeared in its modular form in
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.Fx 9.0 .
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.Pp
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This was the default congestion control algorithm in FreeBSD before
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version
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.Fx 14.0 ,
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after which
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.Xr cc_cubic 4
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replaced it.
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.Pp
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The module was first released in 2007 by James Healy and Lawrence Stewart whilst
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working on the NewTCP research project at Swinburne University of Technology's
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Centre for Advanced Internet Architectures, Melbourne, Australia, which was made
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possible in part by a grant from the Cisco University Research Program Fund at
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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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congestion control module was written by
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.An James Healy Aq Mt jimmy@deefa.com ,
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.An Lawrence Stewart Aq Mt lstewart@FreeBSD.org
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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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Support for TCP ABE was added by
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.An Tom Jones Aq Mt tj@enoti.me .
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.Pp
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This manual page was written by
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.An Lawrence Stewart Aq Mt lstewart@FreeBSD.org .
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