diff --git a/guidelines/microversion_specification.rst b/guidelines/microversion_specification.rst
index e9e3f7d..7bbbd02 100644
--- a/guidelines/microversion_specification.rst
+++ b/guidelines/microversion_specification.rst
@@ -13,7 +13,40 @@ servers, clients adjust their behavior to work with server correctly.
 Versioning
 ----------
 
-TBD
+Versioning of the API should be single monotonic counter taking the form
+X.Y following these conventions:
+
+* X should only be changed if a significant backwards incompatible
+  API change is made which affects the API as whole. That is, something
+  that is only very rarely incremented. X should be changed in the following
+  cases.
+  ** A number of endpoints get replaced by others
+  ** Drastic changes in API consumer workflow
+* Y should be changed when you make any change to the API. Note that this
+  includes semantic changes which may not affect the input or output formats or
+  even originate in the API code layer. We are not distinguishing
+  between backwards compatible and backwards incompatible changes in
+  the versioning system. It will however be made clear in the
+  documentation as to what is a backwards compatible change and what
+  is a backwards incompatible one.
+
+.. note:: Note that these versions numbers do not follow the rules of
+   `Semantic Versioning <http://semver.org/>`_.
+
+There are minimum and maximum versions which are used to describe what the
+server can understand. The minimum and maximum versions are the oldest and
+most recent versions supported. So clients can specify different version in
+the supporting range for each API call on the same server. The minimum version
+can be increased when supporting old clients is too great a burden.
+Increasing the minimum version means breaking the old clients, this happens
+very rarely also.
+
+Each version includes all the changes since minimum version was introduced.
+It is not possible to request the feature introduced at microversion X.Y
+without accepting all the changes before X.Y in the same request.
+For example, you cannot request the feature which was introduced at
+microversion 2.100 without backwards incompatible changes which were
+introduced in microversion 2.99 and earlier.
 
 Client Interaction
 ------------------