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