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diff --git a/share/man/man4/cc_cdg.4 b/share/man/man4/cc_cdg.4 new file mode 100644 index 0000000..c111bd4 --- /dev/null +++ b/share/man/man4/cc_cdg.4 @@ -0,0 +1,155 @@ +.\" +.\" Copyright (c) 2013 Swinburne University of Technology, Melbourne, Australia +.\" All rights reserved. +.\" +.\" 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 July 2, 2013 +.Dt CC_CDG 4 +.Os +.Sh NAME +.Nm cc_cdg +.Nd CDG Congestion Control Algorithm +.Sh DESCRIPTION +CAIA-Delay Gradient (CDG) is a hybrid congestion control algorithm which reacts +to both packet loss and inferred queuing delay. +It attempts to operate as a delay-based algorithm where possible, but utilises +heuristics to detect loss-based TCP cross traffic and will compete effectively +as required. +CDG is therefore incrementally deployable and suitable for use on shared +networks. +.Pp +During delay-based operation, CDG uses a delay-gradient based probabilistic +backoff mechanism, and will also try to infer non congestion related +packet losses and avoid backing off when they occur. +During loss-based operation, CDG essentially reverts to +.Xr cc_newreno 4 Ns - Ns like +behaviour. +.Pp +CDG switches to loss-based operation when it detects that a configurable number +of consecutive delay-based backoffs have had no measurable effect. +It periodically attempts to return to delay-based operation, but will keep +switching back to loss-based operation as required. +.Sh MIB Variables +The algorithm exposes the following variables in the +.Va net.inet.tcp.cc.cdg +branch of the +.Xr sysctl 3 +MIB: +.Bl -tag -width ".Va exp_backoff_scale" +.It Va version +Current algorithm/implementation version number. +.It Va beta_delay +Delay-based window decrease factor as a percentage (on delay-based backoff, w = +w * beta_delay / 100). +Default is 70. +.It Va beta_loss +Loss-based window decrease factor as a percentage (on loss-based backoff, w = +w * beta_loss / 100). +Default is 50. +.It Va exp_backoff_scale +Scaling parameter for the probabilistic exponential backoff. +Default is 2. +.It Va smoothing_factor +Number of samples used for moving average smoothing (0 means no smoothing). +Default is 8. +.It Va loss_compete_consec_cong +Number of consecutive delay-gradient based congestion episodes which will +trigger loss-based CC compatibility. +Default is 5. +.It Va loss_compete_hold_backoff +Number of consecutive delay-gradient based congestion episodes to hold the +window backoff for loss-based CC compatibility. +Default is 5. +.It Va alpha_inc +If non-zero, this enables an experimental mode where CDG's window increase +factor (alpha) is increased by 1 MSS every +.Va alpha_inc +RTTs during congestion avoidance mode. +(Setting +.Va alpha_inc +to 1 results in the most aggressive growth of the window increase factor over +time. +Use higher +.Va alpha_inc +values for slower growth.) +Default is 0. +.El +.Sh SEE ALSO +.Xr cc_chd 4 , +.Xr cc_cubic 4 , +.Xr cc_hd 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 "D. A. Hayes" +.%A "G. Armitage" +.%T "Revisiting TCP Congestion Control using Delay Gradients" +.%J "Networking 2011 Proceedings, Part II" +.%D "May 2011" +.%P "328-341" +.Re +.Rs +.%A "N. Khademi" +.%A "G. Armitage" +.%T "Minimising RTT across homogeneous 802.11 WLANs with CAIA Delay-Gradient TCP (v0.1)" +.%R "CAIA Technical Report 121113A" +.%D "November 2012" +.%U "http://caia.swin.edu.au/reports/121113A/CAIA-TR-121113A.pdf" +.Re +.Sh ACKNOWLEDGEMENTS +Development and testing of this software were made possible in part by grants +from the FreeBSD Foundation and The Cisco University Research Program Fund, a +corporate advised fund of Silicon Valley Community Foundation. +.Sh HISTORY +The +.Nm +congestion control module first appeared in +.Fx 9.2 . +.Pp +The module was first released in 2011 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 was written by +.An David Hayes Aq david.hayes@ieee.org . +This manual page was written by +.An Lawrence Stewart Aq lstewart@FreeBSD.org +and +.An Grenville Armitage Aq garmitage@swin.edu.au . +.Sh BUGS +The underlying algorithm and parameter values are still a work in progress and +may not be optimal for some network scenarios. |
