Ok, so I read this in a book, and also found the the same quoted in Terminal Server news groups, so I guess It’s fair use to quote the stuff…

If remote users are able to type very quickly, screens on Terminal Services clients sometimes tend to hang. This is true for both the RDP and the ICA protocol. To improve terminal server response times, it is possible to change the time that the terminal server waits until it transmits buffered data packages. The shorter this time is, the smaller the data packages are. The time is set via the OutBufDelay registry value. This method increases the frequency with which the data packages are sent. However, this change also gives rise to a slightly increased network load.

The output buffer settings are always related to a protocol as it was created in the Terminal Services Configuration. For RDP, these two registry paths are relevant:

  1. HKLMSystemCurrentControlSetControlTerminal ServerWdsRdpwdTDStcpOutBufDelay
  2.  
  3. HKLMSystemCurrentControlSetControlTerminal ServerWinStationsrdp-tcpOutBufDelay

The parameters specify the number of milliseconds that a terminal server buffers data before transmitting it to the client. The default value is 0×64; half of that value should improve overall system response.

The ICA protocol registry entries are saved under

  1. HKLMSystemCurrentControlSetControlTerminal ServerWdsIcawdTDStcpOutBufDelay
  2.  
  3. HKLMSystemCurrentControlSetControlTerminal ServerWinStationsICA-tcpOutBufDelay