Why is VNC used when RDP is selected for the Managed Session? (4292114)

When connecting to a Managed System using RDP (Interactive or Automatic logon) why is VNC Presented to the end user?

In the above situation VNC is only used to present the session to the user over an encrypted SSH tunnel from the Quest One Privileged Session Manager device while RDP is used to establish the session from the Quest One Privileged Session Manager to the Windows Desktop. To summarize, the flow of traffic from a client to a Windows Desktop (When using RDP Interactive or Automatic logon) resembles the following:

Client -> VNC (encrypted thru an SSH tunnel) -> TPAM or DPA -> RDP -> Windows Desktop