KMS is one of the legal methods to activate Microsoft Windows and Microsoft Office. Activation ensures that the software is obtained from and licensed by Microsoft. KMS is used by volume license customers, usually medium to large businesses, schools, and non-profits. Individual computers do not need to contact Microsoft, although the KMS server does. KMS clients must be activated at least once every 180 days. A KMS client will try to activate once every 7 days, and if it fails it will try again every 2 hours.