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DUMMYNET(4)              BSD Kernel Interfaces Manual              DUMMYNET(4)

NAME
     dummynet -- traffic shaper, bandwidth manager and delay emulator

DESCRIPTION
     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.

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                       - 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.

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

HISTORY
     dummynet 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 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.

Darwin                         October 28, 2002                         Darwin