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diff --git a/docs/usecases/networksim.rst b/docs/usecases/networksim.rst new file mode 100644 index 00000000000..9324c992f00 --- /dev/null +++ b/docs/usecases/networksim.rst @@ -0,0 +1,91 @@ +Generating traffic with VPP +=========================== + +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 ” 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 |