DUMMYNET(4)

NAME

     dummynet -- traffic shaper, bandwidth manager and delay emulator

DESCRIPTION

     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
	   NMBCLUSTERS		     set the amount of network packet buffers
	   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.

SEE ALSO

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

HISTORY

     The dummynet facility was initially implemented as a testing tool for TCP
     congestion control by Luigi Rizzo <luigi@iet.unipi.it>, 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
     policies.