Terminal Services Frequently Asked Questions

Why would a company choose to use Terminal Server?

Terminal Server is a very efficient way to rapidly deploy and maintain applications, since they run entirely on the server, and the end user can access them via a standard RDP or ICA Client. With Terminal Server you could deploy applications to your entire organization/enterprise without ever touching a client computer. Companies that deploy Terminal Server spend significantly less money supporting each desktop, since administrators can assist users remotely, and do not need to visit their computers to update software.

Do I need a VPN to securely access thin-client applications across the Internet?

No. Both RDP and ICA are natively encrypted protocols that transmit only screen data to the remote client and keyboard strokes and mouse clicks from the remote client to the server. Even when you print or copy files to a remote client, this data is encrypted by the RDP or ICA protocol.

Do Terminal Server hosted applications use less bandwidth than applications running over a VPN?

Absolutely, yes. It can often require several hundred kilobits to a few megabits of bandwidth for a single user to run a fat-client application over a VPN, whereas RDP and ICA applications often use as little as 20Kbps and rarely require more than 50-75Kbps per session.

Can I use the advanced features of the Citrix ICA Client without running Citrix Presentation Server on my Terminal Server?

No. In order to use an ICA Client, your Terminal Server MUST be running Citrix MetaFrame or Citrix Presentation Server.

What ports do RDP and ICA Protocols use?

By default Terminal Server listens on TCP Port 3389 for RDP Clients, and Citrix Presentation Server listens on TCP Port 1494 (or 2598 in Presentation Server 4) for ICA Clients.

What if I can't communicate via one of these non-standard ports, and need to connect over HTTP(S) (TCP Ports 80/443)?  

In this situation, you need to connect via a Terminal Server Gateway like 2X Load Balancer for Windows Terminal Services, Tunnel2, or one of the above mentioned Terminal Server Add-ons that includes an SSL Gateway.

How many concurrent user sessions can one terminal server host?  

This is entirely dependent on the server hardware and type of application; however, a Dual Xeon CPU Server with 4GB RAM can usually support 25-75 concurrent sessions. Check here for more server scaling details.

How much bandwidth do I require?

The hardware and bandwidth requirements depend on many factors;

• Which Operating System is running on the terminal server

• Which Applications users are running on the terminal server

• How much printing is done.

• 16 Bit applications and graphics intensive applications should be avoided where possible.

The minimum bandwidth for a useable RDP Session is usually 26.4Kbps:

• 800 x 600 @16 bit colour - 26.4Kbps per session
• 1024 x 768 @256 colours - 24.6Kbps per session

Each increase in screen resolution or color depth requires about 3-4 Kbps more bandwidth.

The amount of RAM required for each RDP Session is about 10-15 MB per user plus whatever their applications need. This is on top of the RAM that you need for the base OS.