1.3.1 Licensing Architecture

The Remote Desktop Protocol: Licensing Extension involves the following components:

  • Remote desktop client: Connects to a terminal server and renders the user interface through which a user interacts with a remote session.

  • Terminal server: Hosts remote desktop sessions and enables interaction with each of these sessions on a connected client device. A reference to terminal server generally refers to a terminal server in app-server mode.

  • Personal terminal server: Hosts remote desktop session where the target operating system is either a client SKU or a terminal server in remote administration mode.

  • License server: Issues licenses to users or devices using remote desktop sessions.

  • Clearing house: Activates license servers and supplies CALs to license servers.

  • Active Directory: Stores licenses issued to users.

  • License Manager: Administers license servers.

The following diagram illustrates the relationship and interaction among these components in a typical terminal server deployment.

Licensing architecture components for terminal server licensing

Figure 1: Licensing architecture components for terminal server licensing

The Remote Desktop Protocol: Licensing Extension facilitates the exchange of licensing information between the Remote Desktop client and the terminal server and is restricted between these two components only. The interaction among the remaining components (for example, between the terminal server and the license server) is not a function of the Remote Desktop Protocol: Licensing Extension.

The license server manages the terminal server CALs. It keeps track of issued and expired per-device terminal server CALs in the license database. The per-user terminal server CALs are stored in Active Directory. The terminal server communicates with the license server, using RPC to accomplish the following tasks:

  • Issue a new terminal server CAL.

  • Upgrade an older version terminal server CAL.

The terminal server interacts with Active Directory to retrieve information on the per-user terminal server CAL when the terminal server is configured in per-user license mode. The license server has to be registered with the Microsoft clearing house before it starts issuing terminal server CALs to the Remote desktop clients. The License Manager is the GUI application for managing the license server. The License Manager provides an interface to the administrator to register the license server with the clearing house. The administrator can use one of two methods to register the license server with the clearing house:

  • HTTPS: The License Manager contacts the clearing house over HTTPS and registers the license server and terminal server CAL key-packs.

  • Telephone/web: The administrator gets the license server and terminal server CAL key-pack registration information manually from the telephone or web and enters the registration information in the interface provided by the License Manager.

The Remote Desktop Protocol: The personal terminal server and the Remote Desktop client do not exchange any licensing information.

For more information about license PDU flows for personal terminal servers, see section 1.3.3.