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:
IPFIREWALL - enable ipfirewall (required for dummynet). IPFIREWALL_VERBOSE - enable firewall output. IPFIREWALL_VERBOSE_LIMIT - limit firewall output. DUMMYNET - enable dummynet operation. NMBCLUSTERS - set the amount of network packet buffers
Generally, the following options are required:
options IPFIREWALL options DUMMYNET
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. Timer granularity is controlled by sysctl(8) variable net.inet.ip.dummynet.hz, which is set to 1000 by default.
SEE ALSO
HISTORY
dummynet 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 then modified to work at the ip and bridging level, integrated with
the IPFW packet filter, and extended to support multiple queueing and
scheduling policies.