About Windows licensing

Windows Terminal Servers require the presence of a client access license (CAL) for every client that connects to the server. Licenses are used by Windows Terminal Servers and clients as a method to track server license use. A Windows Terminal Server communicates with a license server as a license provider and transfers the licenses to connecting clients. Macintosh computers store the license in the /Users/Shared/Microsoft/RDC Crucial Server Information directory and send it to the server on the next connection.

To ease the administration of a Windows Terminal Server, and to handle an instance where the stored license on the client is lost or deleted, the licensing protocol uses the concept of a server grace period as well as a temporary client license. The server grace period is typically 90 days and is enabled upon the first client connection. The server grace period automatically ends when the Windows Terminal Server communicates with a license server for the first time, or when the 90-day period expires, whichever comes first. This allows immediate operation of the Windows Terminal Server in the event no license servers are available; however, it enforces the fact that a license server is ultimately required. In addition, if a license is lost or deleted, the temporary license allows the client to continue connecting until the original license becomes available again. A client access license that is assigned to a client and inactive will become available for reassignment after 89 days of inactivity.

Temporary client licenses can be issued by a license server in the event a client requests a new license, but no more licenses are available. Temporary licenses expire after a set period of time, giving an administrator sufficient time to purchase more licenses before any interruption in client service occurs.

Related topics

System requirements

Advanced features

Configure Windows to accept Remote Desktop connections

Differences between the Windows and Macintosh versions

Troubleshooting licensing error messages