vpp/docs/usecases/networksim.rst
Nathan Skrzypczak 9ad39c026c docs: better docs, mv doxygen to sphinx
This patch refactors the VPP sphinx docs
in order to make it easier to consume
for external readers as well as VPP developers.

It also makes sphinx the single source
of documentation, which simplifies maintenance
and operation.

Most important updates are:

- reformat the existing documentation as rst
- split RELEASE.md and move it into separate rst files
- remove section 'events'
- remove section 'archive'
- remove section 'related projects'
- remove section 'feature by release'
- remove section 'Various links'
- make (Configuration reference, CLI docs,
  developer docs) top level items in the list
- move 'Use Cases' as part of 'About VPP'
- move 'Troubleshooting' as part of 'Getting Started'
- move test framework docs into 'Developer Documentation'
- add a 'Contributing' section for gerrit,
  docs and other contributer related infos
- deprecate doxygen and test-docs targets
- redirect the "make doxygen" target to "make docs"

Type: refactor

Change-Id: I552a5645d5b7964d547f99b1336e2ac24e7c209f
Signed-off-by: Nathan Skrzypczak <nathan.skrzypczak@gmail.com>
Signed-off-by: Andrew Yourtchenko <ayourtch@gmail.com>
2021-10-13 23:22:32 +00:00

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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. Its 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
------------------------------
Heres 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