CAL Revocation on Terminal Services License Server

CAL Revocation is supported only for Windows Server 2008 TS Per-Device CALs. Terminal Services License Server’s automatic CAL reclamation mentioned later in this sidebar applies only to Per Device CALs.

Per-Device CALs are issued to clients for a certain validity period, after which the CAL expires. If the client accesses the terminal server often, the validity of the CAL is renewed accordingly before its expiration. If the client does not access the terminal server for a long time, the CAL eventually expires. The Terminal Services License Server reclaims all the expired CALs periodically with its automatic CAL reclamation mechanism.

Occasionally, an administrator might need to transfer a Per-Device CAL from the client back into the free license pool on the License Server (a process referred to as reclaiming or revoking) when the original client has been permanently removed from the environment and one needs to reallocate the CAL to a different client. Historically, there was no way to do it. An administrator would have had to wait until the CAL expired or lost its validity and was automatically reclaimed by its mechanism. So it was desired to have the License Server support a mechanism to reclaim or revoke CALs.

Using the new Revoke CAL option in TS Licensing Manager, administrators can now reclaim issued CALs and place them back into a free license pool on the License Server. An administrator has to also select the specific client whose CAL needs to be revoked.

But there are certain restrictions on the number of CALs that can be revoked at a given time. This is a restriction imposed by the License Server to prevent misuse. The restriction can be stated as follows: At any given point in time, the number of LH PD CALs in a revoked state cannot exceed 20 percent of the total number of LH PD CALs installed on the License Server. A CAL goes into a revoked state right after revocation, and its state is cleared when it goes past its original expiration date. One can see the list of CALs in the revoked state in the TS Licensing Manager tool by observing the Status column in the client list view. When the administrator has exceeded this limit, he is given a date when further revocation is possible.

Note that TS CALs should not be revoked to affect concurrent licensing. TS CALs can only be revoked when it is reasonable to assume that the machine they were issued to will no longer participate in the environment, for example, when the machine failed. Client machines, no matter how infrequently they may connect, are required to have a TS CAL at all times. This also applies for per user licensing.

Source of Information : Introducing Windows Server 2008