1.3.2.3 RAIL Server/Client Synchronization

A RAIL server synchronizes with the RAIL client over the RDP channel upon connection establishment or when a desktop switch occurs.

RAIL protocol client synchronization

Figure 2: RAIL protocol client synchronization

The synchronization begins with a Desktop Information Order with the WINDOW_ORDER_FIELD_DESKTOP_ARC_BEGAN(0x00000008) flag set in the Hdr field (section 2.2.1.3.3.2.2). Upon receipt of this order, the client clears all previously received information from the server. This order is followed by any number of Windowing Alternate Secondary Drawing Orders describing windows, notification icons, and desktop. Finally, the server sends a Desktop Information Order with the WINDOW_ORDER_FIELD_DESKTOP_ARC_COMPLETED (0x00000004) flag set to signal the end of synchronization data (section 2.2.1.3.3.2.1).

After the initial synchronization, Windowing Alternate Secondary Drawing Orders flow from server to client whenever a change occurs in a window, notification icon, or desktop state.

If the server is not capable of monitoring the desktop (for example, secure desktop), it sends a Desktop Information Order with the WINDOW_ORDER_FIELD_DESKTOP_NONE (0x00000001) flag set in the Hdr field (section 2.2.1.3.3.2.2). Upon receipt of this order, the client clears out all previously received information from the server.