dummynet - traffic shaper, bandwidth manager and delay emulator

CONTENTS

Description
     Kernel Options
See Also
History

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.

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
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.

setsockopt(2), bridge(4), if_bridge(4), ip(4), ipfw(8), sysctl(8)

The dummynet facility was initially implemented as a testing tool for TCP congestion control by
.An Luigi Rizzo Aq 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.

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