DUMYNET(4)              BSD Kernel Interfaces Manual              DUMYNET(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:

       IPFIREWAL               - enable ipfirewall (required for dummynet).
       IPFIREWALVERBOSE       - enable firewall output.
       IPFIREWALVERBOSELIMIT - limit firewall output.
       DUMYNET                 - enable dummynet operation.
       NMBCLUSTERS              - set the amount of network packet buffers
       HZ                       - sets the timer granularity

     Generally, the following options are required:

       options IPFIREWAL
       options DUMYNET
       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 , 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.

Darwin                         October 28, 2002                         Darwin