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

     dummynet -- traffic shaper, bandwidth manager and delay emulator

     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.

     The user interface	for dummynet is	implemented by the ipfw	program, so
     the reader	is referred to the ipfw(8) manpage for a complete description
     of	the capabilities of dummynet and on how	to use it.

     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.
       NMBCLUSTERS		- set the amount of network packet buffers
       HZ			- sets 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), bridge(4), ip(4), ipfw(8), sysctl(8)

     dummynet 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 then modified to
     work at the ip and	bridging level,	integrated with	the IPFW packet	fil-
     ter, and extended to support multiple queueing and	scheduling policies.

FreeBSD	9.2		       October 28, 2002			   FreeBSD 9.2


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