NAME
dummynet —
traffic shaper, bandwidth manager and
delay emulator
DESCRIPTION
Thedummynet 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
dummynetoperation 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
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.