1.\" 2.\" Copyright (c) 2009 Lawrence Stewart <lstewart@FreeBSD.org> 3.\" Copyright (c) 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 Lawrence Stewart under sponsorship from the FreeBSD Foundation. 9.\" 10.\" Redistribution and use in source and binary forms, with or without 11.\" modification, are permitted provided that the following conditions 12.\" are met: 13.\" 1. Redistributions of source code must retain the above copyright 14.\" notice, this list of conditions and the following disclaimer. 15.\" 2. Redistributions in binary form must reproduce the above copyright 16.\" notice, this list of conditions and the following disclaimer in the 17.\" documentation and/or other materials provided with the distribution. 18.\" 19.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 20.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 21.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 22.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE FOR 23.\" ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 24.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 25.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 26.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 27.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 28.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 29.\" SUCH DAMAGE. 30.\" 31.\" $FreeBSD$ 32.\" 33.Dd May 13, 2021 34.Dt CC_NEWRENO 4 35.Os 36.Sh NAME 37.Nm cc_newreno 38.Nd NewReno Congestion Control Algorithm 39.Sh SYNOPSIS 40.In netinet/cc/cc_newreno.h 41.Sh DESCRIPTION 42The NewReno congestion control algorithm is the default for TCP. 43Details about the algorithm can be found in RFC5681. 44.Sh Socket Options 45The 46.Nm 47module supports a number of socket options under TCP_CCALGOOPT (refer to 48.Xr tcp 4 49and 50.Xr mod_cc 9 for details) 51which can 52be set with 53.Xr setsockopt 2 54and tested with 55.Xr getsockopt 2 . 56The 57.Nm 58socket options use this structure defined in 59<sys/netinet/cc/cc_newreno.h>: 60.Bd -literal 61struct cc_newreno_opts { 62 int name; 63 uint32_t val; 64} 65.Ed 66.Bl -tag -width ".Va CC_NEWRENO_BETA_ECN" 67.It Va CC_NEWRENO_BETA 68Multiplicative window decrease factor, specified as a percentage, applied to 69the congestion window in response to a congestion signal per: cwnd = (cwnd * 70CC_NEWRENO_BETA) / 100. 71Default is 50. 72.It Va CC_NEWRENO_BETA_ECN 73Multiplicative window decrease factor, specified as a percentage, applied to 74the congestion window in response to an ECN congestion signal when 75.Va net.inet.tcp.cc.abe=1 76per: cwnd = (cwnd * CC_NEWRENO_BETA_ECN) / 100. 77Default is 80. 78.El 79.Sh MIB Variables 80The algorithm exposes these variables in the 81.Va net.inet.tcp.cc.newreno 82branch of the 83.Xr sysctl 3 84MIB: 85.Bl -tag -width ".Va beta_ecn" 86.It Va beta 87Multiplicative window decrease factor, specified as a percentage, applied to 88the congestion window in response to a congestion signal per: cwnd = (cwnd * 89beta) / 100. 90Default is 50. 91.It Va beta_ecn 92Multiplicative window decrease factor, specified as a percentage, applied to 93the congestion window in response to an ECN congestion signal when 94.Va net.inet.tcp.cc.abe=1 95per: cwnd = (cwnd * beta_ecn) / 100. 96Default is 80. 97.El 98.Sh SEE ALSO 99.Xr cc_cdg 4 , 100.Xr cc_chd 4 , 101.Xr cc_cubic 4 , 102.Xr cc_dctcp 4 , 103.Xr cc_hd 4 , 104.Xr cc_htcp 4 , 105.Xr cc_vegas 4 , 106.Xr mod_cc 4 , 107.Xr tcp 4 , 108.Xr mod_cc 9 109.Rs 110.%A "Mark Allman" 111.%A "Vern Paxson" 112.%A "Ethan Blanton" 113.%T "TCP Congestion Control" 114.%O "RFC 5681" 115.Re 116.Rs 117.%A "Naeem Khademi" 118.%A "Michael Welzl" 119.%A "Grenville Armitage" 120.%A "Gorry Fairhurst" 121.%T "TCP Alternative Backoff with ECN (ABE)" 122.%O "RFC 8511" 123.Re 124.Sh ACKNOWLEDGEMENTS 125Development and testing of this software were made possible in part by grants 126from the FreeBSD Foundation and Cisco University Research Program Fund at 127Community Foundation Silicon Valley. 128.Sh HISTORY 129The 130.Nm 131congestion control algorithm first appeared in its modular form in 132.Fx 9.0 . 133.Pp 134The module was first released in 2007 by James Healy and Lawrence Stewart whilst 135working on the NewTCP research project at Swinburne University of Technology's 136Centre for Advanced Internet Architectures, Melbourne, Australia, which was made 137possible in part by a grant from the Cisco University Research Program Fund at 138Community Foundation Silicon Valley. 139More details are available at: 140.Pp 141http://caia.swin.edu.au/urp/newtcp/ 142.Sh AUTHORS 143.An -nosplit 144The 145.Nm 146congestion control module was written by 147.An James Healy Aq Mt jimmy@deefa.com , 148.An Lawrence Stewart Aq Mt lstewart@FreeBSD.org 149and 150.An David Hayes Aq Mt david.hayes@ieee.org . 151.Pp 152Support for TCP ABE was added by 153.An Tom Jones Aq Mt tj@enoti.me . 154.Pp 155This manual page was written by 156.An Lawrence Stewart Aq Mt lstewart@FreeBSD.org . 157