= Network Simulation =
 * Linux Network emulator [[http://www.linuxfoundation.org/collaborate/workgroups/networking/netem|linuxfoundation]]

 * Delay all packets out eth0
   {{{
   # tc qdisc add dev eth0 root netem delay 100ms
   }}}
 * Delay + 10ms variation, each 25% correlated to previous value.
   {{{
   # tc qdisc change dev eth0 root netem delay 100ms 10ms 25%
   }}}
 * Other options
   * loss 0.3% 25%  (% loss and correlation)
   * duplicate 1%
   * corrupt 0.1%  << corrupts single bit

== Rate control ==
 * There is no rate control built-in to the netem discipline, use Token Bucket Filter (TBF) to limit output.
 {{{
 # tc qdisc add dev eth0 root handle 1:0 netem delay 100ms
 # tc qdisc add dev eth0 parent 1:1 handle 10: tbf rate 256kbit buffer 1600 limit 3000
 # tc -s qdisc ls dev eth0
 qdisc netem 1: limit 1000 delay 100.0ms
   Sent 0 bytes 0 pkts (dropped 0, overlimits 0 )
 qdisc tbf 10: rate 256Kbit burst 1599b lat 26.6ms
   Sent 0 bytes 0 pkts (dropped 0, overlimits 0 )
 }}}

 * To check status
 {{{ 
 tc -s qdisc
 }}}

 * To remove the delay from eth0
 {{{
 tc qdisc del dev eth0 root
 }}}

 * Here is a simple example that only controls traffic to one IP address.
 {{{
 tc qdisc add dev eth0 root handle 1: prio
 tc qdisc add dev eth0 parent 1:3 handle 30: netem \
     delay 200ms 10ms distribution normal
 tc qdisc add dev eth0 parent 30:1 tbf rate 20kbit buffer 1600 limit 3000
 tc filter add dev eth0 protocol ip parent 1:0 prio 3 u32 \
    match ip dst 172.17.34.0/24 flowid 10:3
 }}}