mirror of
https://git.FreeBSD.org/src.git
synced 2024-12-22 11:17:19 +00:00
f772f9fe43
mod_cc.4 and mod_cc.9 respectively to avoid any possible confusion with the cc.1 gcc man page. Update references to these man pages where required. Requested by: Grenville Armitage Approved by: re (kib) MFC after: 3 days
121 lines
4.3 KiB
Groff
121 lines
4.3 KiB
Groff
.\"
|
|
.\" 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 .
|