DUMMYNET(4) MidnightBSD 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 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

NMBCLUSTERS

set the amount of network packet buffers

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), 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.

MidnightBSD 0.3 October 28, 2002 MidnightBSD 0.3