1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
|
.\"
.\" Copyright (c) 2009 Lawrence Stewart <lstewart@FreeBSD.org>
.\" Copyright (c) 2011 The FreeBSD Foundation
.\" All rights reserved.
.\"
.\" Portions of this documentation were written at the Centre for Advanced
.\" Internet Architectures, Swinburne University of Technology, Melbourne,
.\" Australia by Lawrence Stewart 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 13, 2022
.Dt CC_NEWRENO 4
.Os
.Sh NAME
.Nm cc_newreno
.Nd NewReno Congestion Control Algorithm
.Sh SYNOPSIS
.In netinet/cc/cc_newreno.h
.Sh DESCRIPTION
Details about the algorithm can be found in RFC5681.
.Sh Socket Options
The
.Nm
module supports a number of socket options under TCP_CCALGOOPT (refer to
.Xr tcp 4
and
.Xr mod_cc 9 for details)
which can
be set with
.Xr setsockopt 2
and tested with
.Xr getsockopt 2 .
The
.Nm
socket options use this structure defined in
<sys/netinet/cc/cc_newreno.h>:
.Bd -literal
struct cc_newreno_opts {
int name;
uint32_t val;
}
.Ed
.Bl -tag -width ".Va CC_NEWRENO_BETA_ECN"
.It Va CC_NEWRENO_BETA
Multiplicative window decrease factor, specified as a percentage, applied to
the congestion window in response to a congestion signal per: cwnd = (cwnd *
CC_NEWRENO_BETA) / 100.
Default is 50.
.It Va CC_NEWRENO_BETA_ECN
Multiplicative window decrease factor, specified as a percentage, applied to
the congestion window in response to an ECN congestion signal when
.Va net.inet.tcp.cc.abe=1
per: cwnd = (cwnd * CC_NEWRENO_BETA_ECN) / 100.
Default is 80.
.Pp
Note that currently the only way to enable
hystart++ is to enable it via socket option.
When enabling it a value of 1 will enable precise internet-draft (version 4) behavior
(subject to any MIB variable settings), other setting (2 and 3) are experimental.
.El
.Pp
Note that hystart++ requires the TCP stack be able to call to the congestion
controller with both the
.Va newround
function as well as the
.Va rttsample
function.
Currently the only TCP stacks that provide this feedback to the
congestion controller is rack.
.Sh MIB Variables
The algorithm exposes these variables in the
.Va net.inet.tcp.cc.newreno
branch of the
.Xr sysctl 3
MIB:
.Bl -tag -width ".Va beta_ecn"
.It Va beta
Multiplicative window decrease factor, specified as a percentage, applied to
the congestion window in response to a congestion signal per: cwnd = (cwnd *
beta) / 100.
Default is 50.
.It Va beta_ecn
Multiplicative window decrease factor, specified as a percentage, applied to
the congestion window in response to an ECN congestion signal when
.Va net.inet.tcp.cc.abe=1
per: cwnd = (cwnd * beta_ecn) / 100.
Default is 80.
.El
.Sh SEE ALSO
.Xr cc_cdg 4 ,
.Xr cc_chd 4 ,
.Xr cc_cubic 4 ,
.Xr cc_dctcp 4 ,
.Xr cc_hd 4 ,
.Xr cc_htcp 4 ,
.Xr cc_vegas 4 ,
.Xr mod_cc 4 ,
.Xr tcp 4 ,
.Xr mod_cc 9
.Rs
.%A "Mark Allman"
.%A "Vern Paxson"
.%A "Ethan Blanton"
.%T "TCP Congestion Control"
.%O "RFC 5681"
.Re
.Rs
.%A "Naeem Khademi"
.%A "Michael Welzl"
.%A "Grenville Armitage"
.%A "Gorry Fairhurst"
.%T "TCP Alternative Backoff with ECN (ABE)"
.%O "RFC 8511"
.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 HISTORY
The
.Nm
congestion control algorithm first appeared in its modular form in
.Fx 9.0 .
.Pp
The module was first released in 2007 by James Healy and Lawrence Stewart whilst
working on the NewTCP research project at Swinburne University of Technology's
Centre for Advanced Internet Architectures, Melbourne, Australia, which was made
possible in part by a grant from the Cisco University Research Program Fund at
Community Foundation Silicon Valley.
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 James Healy Aq Mt jimmy@deefa.com ,
.An Lawrence Stewart Aq Mt lstewart@FreeBSD.org
and
.An David Hayes Aq Mt david.hayes@ieee.org .
.Pp
Support for TCP ABE was added by
.An Tom Jones Aq Mt tj@enoti.me .
.Pp
This manual page was written by
.An Lawrence Stewart Aq Mt lstewart@FreeBSD.org .
|
