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 limitations, implementing different scheduling and queue management
       policies, 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.

SEE ALSO

       setsockopt(2), if_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 modified to work at the IP and bridging levels, integrated with the ipfw(4) packet  filter,  and
       extended to support multiple queueing and scheduling policies.

Debian                                          October 28, 2002                                     DUMMYNET(4)