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.Dd October 28, 2002
.Dt DUMMYNET 4
.Os Darwin
.Sh NAME
.Nm dummynet
.Nd traffic shaper, bandwidth manager and delay emulator
.Sh DESCRIPTION
.Em dummynet
is a system facility that permits the control of traffic
going through the various network interfaces, by applying bandwidth
and queue size limitations, implementing different scheduling and queue
management policies, and emulating delays and losses.
.Pp
The user interface for
.Em dummynet
is implemented by the
.Nm ipfw
program, so the reader is referred to the
.Xr ipfw 8
manpage for a complete description of the capabilities of
.Nm
and on how to use it.
.Sh KERNEL OPTIONS
The following options in the kernel configuration file are related to
.Nm
operation:
.Bd -literal
  IPFIREWALL               - enable ipfirewall (required for dummynet).
  IPFIREWALL_VERBOSE       - enable firewall output.
  IPFIREWALL_VERBOSE_LIMIT - limit firewall output.
  DUMMYNET                 - enable dummynet operation.
  NMBCLUSTERS              - set the amount of network packet buffers
  HZ                       - sets the timer granularity
.Ed
.Pp
Generally, the following options are required:
.Bd -literal
  options IPFIREWALL
  options DUMMYNET
  options HZ=1000	# strongly recommended
.Ed
.Pp
additionally, one may want to increase the number
of mbuf clusters (used to store network packets) according to the
sum of the bandwidth-delay products and queue sizes of all configured
pipes.
.Sh SEE ALSO
.Xr setsockopt 2 ,
.Xr bridge 4 ,
.Xr ip 4 ,
.Xr ipfw 8 ,
.Xr sysctl 8
.Sh HISTORY
.Nm
was initially implemented as a testing tool for TCP congestion control
by
.An Luigi Rizzo Aq luigi@iet.unipi.it ,
as described on ACM Computer Communication Review, Jan.97 issue.
Later it has been then modified to work at the ip and bridging
level, integrated with the IPFW packet filter, and extended to
support multiple queueing and scheduling policies.