dummynet(4)

NAME

dummynet - traffic shaper, bandwidth manager and delay emu

lator

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 man

agement 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 descrip

tion 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 (re

quired for

dummynet)

IPFIREWALL_VERBOSE enable firewall output
IPFIREWALL_VERBOSE_LIMIT limit firewall output
DUMMYNET enable dummynet opera

tion
NMBCLUSTERS set the amount of net

work packet

buffers

HZ set the timer granulari

ty

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 band

width-delay
products and queue sizes of all configured pipes.

SEE ALSO

setsockopt(2), bridge(4), 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.

BSD October 28, 2002

BSD