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diff --git a/share/man/man4/cc_hd.4 b/share/man/man4/cc_hd.4 new file mode 100644 index 0000000..d0acb34 --- /dev/null +++ b/share/man/man4/cc_hd.4 @@ -0,0 +1,120 @@ +.\" +.\" Copyright (c) 2010-2011 The FreeBSD Foundation +.\" All rights reserved. +.\" +.\" This documentation was 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. Redistributions of source code must retain the above copyright +.\" notice, this list of conditions and the following disclaimer. +.\" 2. Redistributions in binary form must reproduce the above copyright +.\" notice, this list of conditions and the following disclaimer in the +.\" documentation and/or other materials provided with the distribution. +.\" +.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND +.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE +.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE +.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE FOR +.\" ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL +.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS +.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) +.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT +.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY +.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF +.\" SUCH DAMAGE. +.\" +.\" $FreeBSD$ +.\" +.Dd September 15, 2011 +.Dt CC_HD 4 +.Os +.Sh NAME +.Nm cc_hd +.Nd HD Congestion Control Algorithm +.Sh DESCRIPTION +The HD congestion control algorithm is an implementation of the Hamilton +Institute's delay-based congestion control which aims to keep network queuing +delays below a particular threshold (queue_threshold). +.Pp +HD probabilistically reduces the congestion window (cwnd) based on its estimate +of the network queuing delay. +The probability of reducing cwnd is zero at hd_qmin or less, rising to a maximum +at queue_threshold, and then back to zero at the maximum queuing delay. +.Pp +Loss-based congestion control algorithms such as NewReno probe for network +capacity by filling queues until there is a packet loss. +HD competes with loss-based congestion control algorithms by allowing its +probability of reducing cwnd to drop from a maximum at queue_threshold to be +zero at the maximum queuing delay. +This has been shown to work well when the bottleneck link is highly multiplexed. +.Sh MIB Variables +The algorithm exposes the following tunable variables in the +.Va net.inet.tcp.cc.hd +branch of the +.Xr sysctl 3 +MIB: +.Bl -tag -width ".Va queue_threshold" +.It Va queue_threshold +Queueing congestion threshold (qth) in ticks. +Default is 20. +.It Va pmax +Per packet maximum backoff probability as a percentage. +Default is 5. +.It Va qmin +Minimum queuing delay threshold (qmin) in ticks. +Default is 5. +.El +.Sh SEE ALSO +.Xr cc_chd 4 , +.Xr cc_cubic 4 , +.Xr cc_htcp 4 , +.Xr cc_newreno 4 , +.Xr cc_vegas 4 , +.Xr h_ertt 4 , +.Xr mod_cc 4 , +.Xr tcp 4 , +.Xr khelp 9 , +.Xr mod_cc 9 +.Rs +.%A "L. Budzisz" +.%A "R. Stanojevic" +.%A "R. Shorten" +.%A "F. Baker" +.%T "A strategy for fair coexistence of loss and delay-based congestion control algorithms" +.%J "IEEE Commun. Lett." +.%D "Jul 2009" +.%V "13" +.%N "7" +.%P "555-557" +.Re +.Sh 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. +.Sh FUTURE WORK +The Hamilton Institute have recently made some improvements to the algorithm +implemented by this module and have called it Coexistent-TCP (C-TCP). +The improvements should be evaluated and potentially incorporated into this +module. +.Sh HISTORY +The +.Nm +congestion control module first appeared in +.Fx 9.0 . +.Pp +The module was first released in 2010 by David Hayes whilst working on the +NewTCP research project at Swinburne University of Technology's Centre for +Advanced Internet Architectures, Melbourne, Australia. +More details are available at: +.Pp +http://caia.swin.edu.au/urp/newtcp/ +.Sh AUTHORS +.An -nosplit +The +.Nm +congestion control module and this manual page were written by +.An David Hayes Aq david.hayes@ieee.org . |
