diff --git a/docs/report/vpp_performance_tests/test_environment.rst b/docs/report/vpp_performance_tests/test_environment.rst
index 2d71148..173a51b 100644
@@ -5,6 +5,46 @@
+In order to determine any benchmark anomalies (progressions,
+regressions) between releases of a specific data-plane DUT application
+(e.g. VPP, DPDK), the DUT needs to be tested in the same test
+environment, to avoid test environment changes impacting the results and
+clouding the picture.
+In order to enable test system evolution, a mirror scheme is required to
+determine benchmarking anomalies between releases of specific test
+system like CSIT. This is achieved by testing the same DUT application
+version between releases of CSIT test system.
+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:
+- Server hosts hardware firmware and BIOS (motherboard, processsor, NIC(s), accelerator card(s)).
+- Server host Linux operating system versions.
+- Server host Linux configuration.
+- TRex Traffic Generator version, drivers and configuration.
+- CSIT framework code.
+Following is the list of CSIT versions to date:
+- Ver. 1 associated with CSIT rls1908 git branch as of 2019-08-21.
+- Ver. 2 associated with CSIT rls2001 git branch as of 2020-03-27.
+- Ver. 3 interim associated with master branch as of 2020-xx-xx.
+- Ver. 4 associated with CSIT rls2005 git branch as of 2020-06-24.
+To identify performance changes due to VPP code changes 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 has been marked up with
+RCA analysis. See Current vs Previous Release and Known Issues.
+CSIT environment ver. 4 has been evaluated against the ver. 2 by
+benchmarking VPP v20.01.0 in both environrment versions.
.. include:: ../introduction/test_environment_intro.rst
.. include:: ../introduction/test_environment_sut_conf_1.rst