Volume Activation allows volume license customers to automate the activation process so that it is transparent to users. Volume Activation applies to computers that are covered under a Volume Licensing program. It is used strictly as a tool for activation, and it is not tied to license invoicing or billing.
Volume Activation provides two models for completing volume activations: Key Management Service (KMS) and Multiple Activation Key (MAK). KMS allows organizations to activate systems within their network, and MAK activates systems on a one-time basis by using the hosted activation services provided by Microsoft. Customers can use either or both key types to activate systems in their environments.
Key Management Service
With KMS, IT pros can complete activations on their local network, eliminating the need for individual computers to connect to Microsoft for product activation. KMS is a lightweight service that does not require a dedicated system and can easily be co-hosted on a system that provides other services. By default, volume editions of Windows 7 and Windows Server 2008 R2 connect to a system that hosts the KMS service to request activation. No action is required from the user.
KMS requires a minimum number of computers (physical or virtual machines) in a network environment. The organization must have at least five computers to activate Windows Server 2008 R2 and at least 25 computers to activate clients that are running Windows 7. These minimums are referred to as activation thresholds.
To use KMS activation with Windows 7, the computer must have the qualifying OS license (often obtained through OEMs as part of the new PC purchase) and contain a Windows Marker in BIOS.
Multiple Activation Key
MAK is used for one-time activation with Microsoft’s hosted activation services. There are two ways to activate computers using MAK. The first method is MAK Independent activation, which requires that each computer independently connect and be activated with Microsoft either over the Internet or by telephone. The second method is MAK Proxy activation. With this method, a computer acting as a MAK proxy gathers activation information from multiple computers on the network, and then sends a centralized activation request on their behalf. MAK Proxy activation is configured using the Volume Activation Management Tool (VAMT).
Note KMS is the default key for Volume Activation clients. Using MAK activation requires installing a MAK key
Volume Activation Models