137 lines
4.7 KiB
Groff
137 lines
4.7 KiB
Groff
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.\"
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.\" Copyright (c) 2008 Lawrence Stewart <lstewart@FreeBSD.org>
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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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.\" Portions of this documentation were written at the Centre for Advanced
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.\" Internet Architectures, Swinburne University, Melbourne, Australia by
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.\" David Hayes 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 15, 2011
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.Dt CC_HTCP 4
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.Os
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.Sh NAME
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.Nm cc_htcp
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.Nd H-TCP Congestion Control Algorithm
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.Sh DESCRIPTION
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The H-TCP congestion control algorithm was designed to provide increased
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throughput in fast and long-distance networks.
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It attempts to maintain fairness when competing with legacy NewReno TCP in lower
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speed scenarios where NewReno is able to operate adequately.
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.Pp
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The congestion window is increased as a function of the time elapsed since the
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last congestion event.
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The window increase algorithm operates like NewReno for the first second after a
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congestion event, and then switches to a high-speed mode based on a quadratic
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increase function.
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.Pp
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The implementation was done in a clean-room fashion, and is based on the
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Internet Draft and other documents referenced in the
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.Sx SEE ALSO
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section below.
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.Sh MIB Variables
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The algorithm exposes the following tunable variables in the
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.Va net.inet.tcp.cc.htcp
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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 adaptive_backoff"
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.It Va adaptive_backoff
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Controls use of the adaptive backoff algorithm, which is designed to keep
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network queues non-empty during congestion recovery episodes.
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Default is 0 (disabled).
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.It Va rtt_scaling
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Controls use of the RTT scaling algorithm, which is designed to make congestion
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window increase during congestion avoidance mode invariant with respect to RTT.
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Default is 0 (disabled).
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.El
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.Sh SEE ALSO
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.Xr cc 4 ,
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.Xr cc_chd 4 ,
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.Xr cc_cubic 4 ,
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.Xr cc_hd 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 cc 9
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.Rs
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.%A "D. Leith"
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.%A "R. Shorten"
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.%T "H-TCP: TCP Congestion Control for High Bandwidth-Delay Product Paths"
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.%U "http://tools.ietf.org/id/draft-leith-tcp-htcp-06.txt"
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.Re
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.Rs
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.%A "D. Leith"
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.%A "R. Shorten"
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.%A "T. Yee"
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.%T "H-TCP: A framework for congestion control in high-speed and long-distance networks"
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.%B "Proc. PFLDnet"
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.%D "2005"
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.Re
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.Rs
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.%A "G. Armitage"
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.%A "L. Stewart"
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.%A "M. Welzl"
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.%A "J. Healy"
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.%T "An independent H-TCP implementation under FreeBSD 7.0: description and observed behaviour"
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.%J "SIGCOMM Comput. Commun. Rev."
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.%V "38"
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.%N "3"
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.%D "July 2008"
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.%P "27-38"
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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 module first appeared in
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.Fx 9.0 .
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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's Centre for
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Advanced Internet Architectures, Melbourne, Australia, which was made possible
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in part by a grant from the Cisco University Research Program Fund at Community
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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 jimmy@deefa.com
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and
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.An Lawrence Stewart Aq lstewart@FreeBSD.org .
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.Pp
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This manual page was written by
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.An Lawrence Stewart Aq lstewart@FreeBSD.org
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and
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.An David Hayes Aq david.hayes@ieee.org .
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