Add emulation of delay profiles, which lets you model various

types of MAC overheads such as preambles, link level retransmissions
and more.

Note- this commit changes the userland/kernel ABI for pipes
(but not for ordinary firewall rules) so you need to rebuild
kernel and /sbin/ipfw to use dummynet features.

Please check the manpage for details on the new feature.

The MFC would be trivial but it breaks the ABI, so it will
be postponed until after 7.2 is released.

Interested users are welcome to apply the patch manually
to their RELENG_7 tree.

Work supported by the European Commission, Projects Onelab and
Onelab2 (contract 224263).

1 files changed, 86 insertions, 1 deletions

diff --git a/sbin/ipfw/ipfw.8 b/sbin/ipfw/ipfw.8
index 44eb05c..4a6d203 100644
--- a/sbin/ipfw/ipfw.8
+++ b/sbin/ipfw/ipfw.8
@@ -1,7 +1,7 @@
 .\"
 .\" $FreeBSD$
 .\"
-.Dd April 5, 2009
+.Dd April 9, 2009
 .Dt IPFW 8
 .Os
 .Sh NAME
@@ -1942,6 +1942,80 @@ with
 to reduce
 the granularity to 1ms or less).
 Default value is 0, meaning no delay.
+.Pp
+.It Cm profile Ar filename
+A file specifying the additional overhead incurred in the transmission
+of a packet on the link.
+.Pp
+Some link types introduce extra delays in the transmission
+of a packet, e.g. because of MAC level framing, contention on
+the use of the channel, MAC level retransmissions and so on.
+From our point of view, the channel is effectively unavailable
+for this extra time, which is constant or variable depending
+on the link type. Additionally, packets may be dropped after this
+time (e.g. on a wireless link after too many retransmissions).
+We can model the additional delay with an empirical curve
+that represents its distribution.
+.Bd -literal -offset indent
+      cumulative probability
+      1.0 ^
+          |
+      L   +-- loss-level          x
+          |                 ******
+          |                *
+          |           *****
+          |          *
+          |        **
+          |       *
+          +-------*------------------->
+                      delay
+.Ed
+The empirical curve may have both vertical and horizontal lines.
+Vertical lines represent constant delay for a range of
+probabilities.
+Horizontal lines correspond to a discontinuty in the delay
+distribution: the pipe will use the largest delay for a
+given probability.
+.Pp
+The file format is the following, with whitespace acting as
+a separator and '#' indicating the beginning a comment:
+.Bl -tag -width indent
+.It Cm samples Ar N
+the number of samples used in the internal
+representation (2..1024; default 100);
+.It Cm loss-level Ar L
+The probability above which packets are lost.
+(0.0 <= L <= 1.0, default 1.0 i.e. no loss);
+.It Cm name Ar identifier
+Optional a name (listed by "ipfw pipe show")
+to identify the distribution;
+.It Cm "delay prob" | "prob delay"
+One of these two lines is mandatory and defines
+the format of the following lines with data points.
+.It Ar XXX Ar YYY
+2 or more lines representing points in the curve,
+with either delay or probability first, according
+to the chosen format.
+The unit for delay is milliseconds.
+Data points do not need to be ordered or equal to the number
+specified in the "samples" line. ipfw will sort and interpolate
+the curve as needed.
+.El
+.Pp
+Example of a profile file:
+.Bd -literal -offset indent
+name    bla_bla_bla
+samples 100
+loss-level    0.86
+prob    delay
+0       200	# minimum overhead is 200ms
+0.5     200
+0.5     300
+0.8     1000
+0.9     1300
+1       1300
+#configuration file end
+.Ed
 .El
 .Pp
 The following parameters can be configured for a queue:
@@ -2917,10 +2991,17 @@ API based upon code written by
 .An Daniel Boulet
 for BSDI.
 .Pp
+Dummynet has been introduced by Luigi Rizzo in 1997-1998.
+.Pp
 Some early work (1999-2000) on the
 .Nm dummynet
 traffic shaper supported by Akamba Corp.
 .Pp
+The ipfw core (ipfw2) has been completely redesigned and
+reimplemented by Luigi Rizzo in summer 2002. Further
+actions and
+options have been added by various developer over the years.
+.Pp
 .An -nosplit
 In-kernel NAT support written by
 .An Paolo Pisati Aq piso@FreeBSD.org
@@ -2933,6 +3014,10 @@ support has been developed by
 The primary developers and maintainers are David Hayes and Jason But.
 For further information visit:
 .Aq http://www.caia.swin.edu.au/urp/SONATA
+.Pp
+Delay profiles have been developed by Alessandro Cerri and
+Luigi Rizzo, supported by the
+European Commission within Projects Onelab and Onelab2.
 .Sh BUGS
 The syntax has grown over the years and sometimes it might be confusing.
 Unfortunately, backward compatibility prevents cleaning up mistakes