DESCRIPTIONThe 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.
Kernel OptionsThe following options in the kernel configuration file are related to operation:
- enable ipfirewall (required for )
- enable firewall output
- limit firewall output
- enable operation
- 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.
HISTORYThe facility was initially implemented as a testing tool for TCP congestion control by An Luigi Rizzo Aq [email protected] , 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.