+.. _test_environment_versioning:
+
+Environment Versioning
+----------------------
+
+CSIT test environment versioning has been introduced to track
+modifications of the test environment.
+
+Any benchmark anomalies (progressions, regressions) between releases of
+a DUT application (e.g. VPP, DPDK), are determined by testing it in the
+same test environment, to avoid test environment changes clouding the
+picture.
+
+A mirror approach is introduced to determine benchmarking anomalies due
+to the test environment change. This is achieved by testing the same DUT
+application version between releases of CSIT test system. This works
+under the assumption that the behaviour of the DUT is deterministic
+under the test conditions.
+
+CSIT test environment versioning scheme ensures integrity of all the
+test system components, including their HW revisions, compiled SW code
+versions and SW source code, within a specific CSIT version. Components
+included in the CSIT environment versioning include:
+
+- **HW** Server hardware firmware and BIOS (motherboard, processsor,
+ NIC(s), accelerator card(s)), tracked in CSIT branch in
+ :file:`./docs/lab/<server_platform_name>_hw_bios_cfg.md`, e.g. `Xeon
+ Skylake servers
+ <https://git.fd.io/csit/tree/docs/lab/testbeds_sm_skx_hw_bios_cfg.md#n556>`_.
+- **Linux** Server Linux OS version and configuration, tracked in CSIT
+ Reports in `SUT Settings
+ <https://docs.fd.io/csit/master/report/vpp_performance_tests/test_environment.html#sut-settings-linux>`_
+ and `Pre-Test Server Calibration
+ <https://docs.fd.io/csit/master/report/vpp_performance_tests/test_environment.html#pre-test-server-calibration>`_.
+- **TRex** TRex Traffic Generator version, drivers and configuration
+ tracked in `TG Settings
+ <https://docs.fd.io/csit/master/report/vpp_performance_tests/test_environment.html#tg-settings-trex>`_.
+- **CSIT** CSIT framework code tracked in CSIT release branches.
+
+Following is the list of CSIT versions to date:
+
+- Ver. 1 associated with CSIT rls1908 branch (`HW
+ <https://git.fd.io/csit/tree/docs/lab?h=rls1908>`_, `Linux
+ <https://docs.fd.io/csit/rls1908/report/vpp_performance_tests/test_environment.html#sut-settings-linux>`_,
+ `TRex
+ <https://docs.fd.io/csit/rls1908/report/vpp_performance_tests/test_environment.html#tg-settings-trex>`_,
+ `CSIT <https://git.fd.io/csit/tree/?h=rls1908>`_).
+- Ver. 2 associated with CSIT rls2001 branch (`HW
+ <https://git.fd.io/csit/tree/docs/lab?h=rls2001>`_, `Linux
+ <https://docs.fd.io/csit/rls2001/report/vpp_performance_tests/test_environment.html#sut-settings-linux>`_,
+ `TRex
+ <https://docs.fd.io/csit/rls2001/report/vpp_performance_tests/test_environment.html#tg-settings-trex>`_,
+ `CSIT <https://git.fd.io/csit/tree/?h=rls2001>`_).
+- Ver. 4 associated with CSIT rls2005 branch (`HW
+ <https://git.fd.io/csit/tree/docs/lab?h=rls2005>`_, `Linux
+ <https://docs.fd.io/csit/rls2005/report/vpp_performance_tests/test_environment.html#sut-settings-linux>`_,
+ `TRex
+ <https://docs.fd.io/csit/rls2005/report/vpp_performance_tests/test_environment.html#tg-settings-trex>`_,
+ `CSIT <https://git.fd.io/csit/tree/?h=rls2005>`_).
+
+To identify performance changes due to VPP code development from
+v20.01.0 to v20.05.0, both have been tested in CSIT environment ver. 4
+and compared against each other. All substantial progressions and
+regressions have been marked up with RCA analysis. See
+:ref:`vpp_throughput_comparisons` and :ref:`vpp_known_issues`.
+
+CSIT environment ver. 4 has been evaluated against the ver. 2 by
+benchmarking VPP v20.01.0 in both environment versions.
+