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DUMMYNET(4)	       FreeBSD Kernel Interfaces Manual		   DUMMYNET(4)

     dummynet -- traffic shaper, bandwidth manager and delay emulator

     The dummynet system facility permits the control of traffic going through
     the various network interfaces, by	applying bandwidth and queue size lim-
     itations, implementing different scheduling and queue management poli-
     cies, and emulating delays	and losses.

     The user interface	for dummynet is	implemented by the ipfw(8) utility, so
     please refer to the ipfw(8) manpage for a complete	description of the
     dummynet capabilities and how to use it.

   Kernel Options
     The following options in the kernel configuration file are	related	to
     dummynet operation:

	   IPFIREWALL		     enable ipfirewall (required for dummynet)
	   IPFIREWALL_VERBOSE	     enable firewall output
	   IPFIREWALL_VERBOSE_LIMIT  limit firewall output
	   DUMMYNET		     enable dummynet operation
	   HZ			     set the timer granularity

     Generally,	the following options are required:

	   options IPFIREWALL
	   options DUMMYNET
	   options HZ=1000	   # strongly recommended

     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.

     setsockopt(2), if_bridge(4), ip(4), ipfw(8), sysctl(8)

     The dummynet facility was initially implemented as	a testing tool for TCP
     congestion	control	by Luigi Rizzo <>, as	described on
     ACM Computer Communication	Review,	Jan.97 issue.  Later it	has been modi-
     fied to work at the IP and	bridging levels, integrated with the ipfw(4)
     packet filter, and	extended to support multiple queueing and scheduling

FreeBSD	13.0		       October 28, 2002			  FreeBSD 13.0


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