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diff --git a/docs/usecases/networksim.md b/docs/usecases/networksim.md new file mode 100644 index 00000000000..817ddf82a29 --- /dev/null +++ b/docs/usecases/networksim.md @@ -0,0 +1,90 @@ +Network Simulator Plugin +======================== + +Vpp includes a fairly capable network simulator plugin, which can +simulate real-world round-trip times and a configurable network packet +loss rate. It's perfect for evaluating the performance of a TCP stack +under specified delay/bandwidth/loss conditions. + +The "nsim" plugin cross-connects two physical interfaces at layer 2, +introducing the specified delay and network loss +parameters. Reconfiguration on the fly is OK, with the proviso that +packets held in the network simulator scheduling wheel will be lost. + +Configuration +------------- + +Configuration by debug CLI is simple. First, specify the simulator +configuration: unidirectional delay (half of the desired RTT), the +link bandwidth, and the expected average packet size. These parameters +allow the network simulator allocate the right amount of buffering to +produce the requested delay/bandwidth product. + +``` + set nsim delay 25.0 ms bandwidth 10 gbit packet-size 128 +``` + +To simulate network packet drops, add either "packets-per-drop <nnnnn>" or +"drop-fraction [0.0 ... 1.0]" parameters: + +``` + set nsim delay 25.0 ms bandwidth 10 gbit packet-size 128 packets-per-drop 10000 +``` +Remember to configure the layer-2 cross-connect: + +``` + nsim enable-disable <interface-1> <interface-2> +``` + +Packet Generator Configuration +------------------------------ + +Here's a unit-test configuration for the vpp packet generator: + +``` + loop cre + set int ip address loop0 11.22.33.1/24 + set int state loop0 up + + loop cre + set int ip address loop1 11.22.34.1/24 + set int state loop1 up + + set nsim delay 1.0 ms bandwidth 10 gbit packet-size 128 packets-per-drop 1000 + nsim enable-disable loop0 loop1 + + packet-generator new { + name s0 + limit 10000 + size 128-128 + interface loop0 + node ethernet-input + data { IP4: 1.2.3 -> 4.5.6 + UDP: 11.22.33.44 -> 11.22.34.44 + UDP: 1234 -> 2345 + incrementing 114 + } + } +``` + +For extra realism, the network simulator drops any specific packet +with the specified probability. In this example, we see that slight +variation from run to run occurs as it should. + +``` + DBGvpp# pa en + DBGvpp# sh err + Count Node Reason + 9991 nsim Packets buffered + 9 nsim Network loss simulation drop packets + 9991 ethernet-input l3 mac mismatch + + DBGvpp# clear err + DBGvpp# pa en + DBGvpp# sh err + sh err + Count Node Reason + 9993 nsim Packets buffered + 7 nsim Network loss simulation drop packets + 9993 ethernet-input l3 mac mismatch +``` |