DUMMYNET(4) FreeBSD Kernel Interfaces Manual 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
limitations, implementing different scheduling and queue management
policies, and emulating delays and losses.
The user interface for dummynet is implemented by the dnctl(8) utility,
so please refer to the dnctl(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 (if dummynet is to be
used with ipfw)
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), pf.conf(5), dnctl(8), 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.
FreeBSD 15.1-STABLE-HBSD September 10, 2021 DUMMYNET(4)