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/share/man/man4/cc_htcp.4

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  1.\"
  2.\" Copyright (c) 2008 Lawrence Stewart <lstewart@FreeBSD.org>
  3.\" Copyright (c) 2010-2011 The FreeBSD Foundation
  4.\" All rights reserved.
  5.\"
  6.\" Portions of this documentation were written at the Centre for Advanced
  7.\" Internet Architectures, Swinburne University of Technology, Melbourne,
  8.\" Australia by David Hayes under sponsorship from the FreeBSD Foundation.
  9.\"
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 11.\" modification, are permitted provided that the following conditions
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 31.\" $FreeBSD$
 32.\"
 33.Dd September 15, 2011
 34.Dt CC_HTCP 4
 35.Os
 36.Sh NAME
 37.Nm cc_htcp
 38.Nd H-TCP Congestion Control Algorithm
 39.Sh DESCRIPTION
 40The H-TCP congestion control algorithm was designed to provide increased
 41throughput in fast and long-distance networks.
 42It attempts to maintain fairness when competing with legacy NewReno TCP in lower
 43speed scenarios where NewReno is able to operate adequately.
 44.Pp
 45The congestion window is increased as a function of the time elapsed since the
 46last congestion event.
 47The window increase algorithm operates like NewReno for the first second after a
 48congestion event, and then switches to a high-speed mode based on a quadratic
 49increase function.
 50.Pp
 51The implementation was done in a clean-room fashion, and is based on the
 52Internet Draft and other documents referenced in the
 53.Sx SEE ALSO
 54section below.
 55.Sh MIB Variables
 56The algorithm exposes the following tunable variables in the
 57.Va net.inet.tcp.cc.htcp
 58branch of the
 59.Xr sysctl 3
 60MIB:
 61.Bl -tag -width ".Va adaptive_backoff"
 62.It Va adaptive_backoff
 63Controls use of the adaptive backoff algorithm, which is designed to keep
 64network queues non-empty during congestion recovery episodes.
 65Default is 0 (disabled).
 66.It Va rtt_scaling
 67Controls use of the RTT scaling algorithm, which is designed to make congestion
 68window increase during congestion avoidance mode invariant with respect to RTT.
 69Default is 0 (disabled).
 70.El
 71.Sh SEE ALSO
 72.Xr cc_chd 4 ,
 73.Xr cc_cubic 4 ,
 74.Xr cc_hd 4 ,
 75.Xr cc_newreno 4 ,
 76.Xr cc_vegas 4 ,
 77.Xr mod_cc 4 ,
 78.Xr tcp 4 ,
 79.Xr mod_cc 9
 80.Rs
 81.%A "D. Leith"
 82.%A "R. Shorten"
 83.%T "H-TCP: TCP Congestion Control for High Bandwidth-Delay Product Paths"
 84.%U "http://tools.ietf.org/id/draft-leith-tcp-htcp-06.txt"
 85.Re
 86.Rs
 87.%A "D. Leith"
 88.%A "R. Shorten"
 89.%A "T. Yee"
 90.%T "H-TCP: A framework for congestion control in high-speed and long-distance networks"
 91.%B "Proc. PFLDnet"
 92.%D "2005"
 93.Re
 94.Rs
 95.%A "G. Armitage"
 96.%A "L. Stewart"
 97.%A "M. Welzl"
 98.%A "J. Healy"
 99.%T "An independent H-TCP implementation under FreeBSD 7.0: description and observed behaviour"
100.%J "SIGCOMM Comput. Commun. Rev."
101.%V "38"
102.%N "3"
103.%D "July 2008"
104.%P "27-38"
105.Re
106.Sh ACKNOWLEDGEMENTS
107Development and testing of this software were made possible in part by grants
108from the FreeBSD Foundation and Cisco University Research Program Fund at
109Community Foundation Silicon Valley.
110.Sh HISTORY
111The
112.Nm
113congestion control module first appeared in
114.Fx 9.0 .
115.Pp
116The module was first released in 2007 by James Healy and Lawrence Stewart whilst
117working on the NewTCP research project at Swinburne University of Technology's
118Centre for Advanced Internet Architectures, Melbourne, Australia, which was made
119possible in part by a grant from the Cisco University Research Program Fund at
120Community Foundation Silicon Valley.
121More details are available at:
122.Pp
123http://caia.swin.edu.au/urp/newtcp/
124.Sh AUTHORS
125.An -nosplit
126The
127.Nm
128congestion control module was written by
129.An James Healy Aq jimmy@deefa.com
130and
131.An Lawrence Stewart Aq lstewart@FreeBSD.org .
132.Pp
133This manual page was written by
134.An Lawrence Stewart Aq lstewart@FreeBSD.org
135and
136.An David Hayes Aq david.hayes@ieee.org .