— traffic shaper, bandwidth
manager and delay emulator
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
utility, so please refer to the
manpage for a complete description of the
capabilities and how to use it.
The following options in the kernel configuration file are related to
- enable ipfirewall (required for
- enable firewall output
- limit firewall output
- enable dummynet operation
- set the timer granularity
Generally, the following options are required:
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.
facility was initially implemented as a testing
tool for TCP congestion control by
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
packet filter, and extended to support multiple
queueing and scheduling policies.