Installing and Configuring Fault-Tolerant Terminal Services

Terminal Services reliability and performance can be maintained and improved by implementing fault tolerance using Windows Server 2003 network load balancing and/or Windows Server 2003 Session Directory server.

Network Load Balancing Terminal Server

Terminal Servers can be easily scaled out using Windows Server 2003 NLB. Creating NLB clusters to spread server load across multiple Terminal Servers not only increases fault tolerance, but also allows the administrator to take a particular server offline for maintenance without affecting the availability of the Terminal Server environment.

Using NLB clusters along with Windows Server 2003 Session Directory server enables an end user to reconnect to a disconnected Terminal Server session that is currently running on an NLB cluster node. This way, users who want to close a session and return to it later can be assured that they will connect to the same session. Using NLB without Session Directory server could result in a disconnected user creating an entirely new session on a different cluster node when attempting to reconnect to the existing session.

To make a Terminal Server running on Windows Server 2003 part of an NLB cluster, follow these steps:

1.	Log on to the Terminal Server with Administrative rights.
2.	Open the property page of the desired network adapter.
3.	Add the cluster IP address to the network adapter in the Internet Protocol (TCP/IP) Advanced section and click OK twice to return to the network adapter property page.
4.	Check the Network Load Balancing box on the General tab of the network adapter property page.
5.	To make specific changes to the Network Load Balancing settings, click Properties.
6.	Enter the cluster IP address and full Internet name in the Cluster Parameters page, and on the Host Parameters page, enter Priority (unique host identifier) and the dedicated IP address.
7.	On the Port Rules page, configure a port rule to allow port TCP 3389 (RDP) and configure only single or class C affinity filtering mode. Do not use the None filtering mode because Terminal Server sessions will fail.
8.	Disable any unnecessary port ranges by creating additional port rules. Refer to Figure 27.11 for basic Terminal Server port rules. Click Next and then Finish when completed. Figure 27.11. Choosing port rules for the Terminal Server system.

You need to perform the preceding steps on each server in the cluster, or you can configure all the servers in the cluster at one time by using the Network Load Balancing Manager, which is discussed in Chapter 31, "System-Level Fault tolerance (Clustering/Network Load Balancing)."

Configuring the Session Directory Server

To make use of a Session Directory server, a Terminal Server load-balanced cluster must be built. It can be a Microsoft NLB cluster or a cluster built using a hardware-based loadbalancing device.

Session Directory server service can be run from any Windows Server 2003 Enterprise or Datacenter server. To create a Session Directory server, follow these steps:

1.	Open the Services applet on the server that will be the Session Directory server. The Session Directory server does not need to run a Terminal Services server but needs to be running on a Windows Server 2003 Enterprise or Datacenter server.
2.	Find the Terminal Services Session Directory service and double-click it.
3.	On the General tab, in the section labeled Startup Type, change the startup type to Automatic.
4.	Click Apply to submit the change and click Start to begin the Session Directory service. Click OK to close the service window and close the services console.
5.	After the service is started, each terminal server computer object that will use the Session Directory server must be added to the newly created local group called Session Directory Computers. This task can be performed using the Local Users and Computers applet in Computer Management on a Session Directory Server that is a domain member server, or it can be performed using Active Directory Users and Computers if the Session Directory server is a domain controller.

Now you must configure the nodes in the Terminal Server cluster to use the Session Directory server. On individual nodes in the cluster, use the Terminal Services Configuration snap-in and select the Server Settings section to configure the following settings.

1.	Set the Restrict Each User to One Session setting to Yes.
2.	Enable the next setting, Session Directory, shown in Figure 27.12, by checking the Join Session Directory box. Figure 27.12. Terminal Services session directory settings.
3.	Add the fully qualified domain names of the Terminal Server cluster and the Session Directory server.
4.	Choose whether the clients will reconnect to the virtual cluster IP address or the actual dedicated IP address of the server node. Connecting to the virtual cluster IP address is preferred. Leaving this option unchecked is preferred for Windows 2000 and Windows Server 2003 Terminal Server clients.
5.	When you're finished, click OK to return to the Terminal Server Configuration snap-in.