3.1.4 Higher-Layer Triggered Events
The announcement of different devices can be triggered by an event, such as when a user has successfully logged on to a terminal server. This behavior ensures that the required devices are visible in the different stages of the logon process. For example, when the protocol is first established, only the smart card devices are announced, because only those devices are required for the logon process. After logon completes, the rest of the devices can be announced to the server. The logged-on event triggers the server to send a Server User Logged On (section 2.2.2.5) packet, which the client can use as an indication that the server is logged on.
The announcement of additional drives by the client is triggered when devices are added to the client machine. After the devices are added to the client machine, the client SHOULD announce the new drives to the server using a Client Device List Announce (section 2.2.3.1) message. When the device is removed from the client, the client sends a Client Drive Device List Remove (section 2.2.3.2) message.
I/O requests are generated in response to I/O calls that server applications make on the redirected device.