Remote Desktop Protocol (RDP) is a multi-channel compatible protocol that allows separate virtual channels to carry presentation data, serial device communication, license information, highly encrypted data (keyboard and mouse activity), etc.
RDP is used to provide a GUI to another computer on the network. RDP happens to be used with Windows terminal servers for providing fast admittance with the near-real-time broadcast of mouse movements and keystrokes over low-bandwidth connections even.
Sometimes a user who is accessing an application remotely may want to leave the application running on the remote computer but shut down the local computer. Therefore, the user closes the local application without logging out of the remote application. Post reconnecting to the remote machine, the user must be able to continue with the remote application. To provide this functionality, the Citrix ADC RDP implementation respects the routing token (cookie) set by the Broker or Terminal Services Session Directory so that the client can reconnect to the same terminal server that it was previously connected to. The Session Directory, implemented in Windows 2003 Terminal Server, is known as Broker in Windows 2008 Terminal Server.
When a TCP connection is established between the client and the load balancing virtual server, Citrix ADC applies the specified load balancing method and forwards the request to one of the terminal servers. The terminal server checks the session directory to determine if the client has a session running on any other terminal server in the domain.
If there happens not to be an active session on any kind of different terminal server, it happens to respond by serving the client’s request, and the Citrix ADC appliance onwards the response to the client.
If there is an active session on any other terminal server, the terminal server that receives the request inserts a cookie (called a routing token) with the details of the active session and returns the packets to the Citrix ADC appliance, which returns the package to the customer. The server use to close the linking with the client.
The user on the client computer experiences a continuation of the service and does not have to take any specific action.
Note: The Windows Session Directory element use to require the Remote Desktop client that was first released with Windows XP. If a session with a Windows 2000 or Windows NT 4.0 Terminal Server client is disconnected and the client reconnects, the server to which the connection is established is selected by the load balancing algorithm.
For more effectual monitoring of an RDP service, on top of the defaulting monitor, you will be able to configure a script monitor aimed for the RDP protocol, buy RDP and start monitoring. When configuring the script monitor, the Citrix ADC opens a TCP connection to the specified server and sends an RDP packet. The monitor happens to mark the service as UP only in the event that it uses to receive a validation of the connection from the physical server. Therefore, from the script monitor, the Citrix ADC can tell if the RDP service is ready to service a request.