Overview of the Session Directory Technology in Terminal Services

This article describes the Session Directory technology that is now available on Windows Server 2003 computers. With this technology, you can reconnect to a Terminal Services session from which you have disconnected.

The Terminal Services Session Directory service is a database that keeps track of sessions on terminal servers in a load-balanced cluster. In addition, this service provides the information that is used at connection time to connect you to an existing session.

Load balancing pools the processing resources of several servers by using the TCP/IP networking protocol. You can use this service with a cluster of terminal servers to scale the performance of a single terminal server by distributing sessions across multiple servers. Terminal Services Connection Management keeps track of disconnected sessions on the cluster, and ensures that users are automatically connected to their disconnected sessions on the same server. The requirements for Session Directory are:

• A network load-balancing solution such as Network Load Balancing, DNS round-robin, or a third-party solution.
• Two or more terminal servers that are logically grouped into a terminal server cluster.
• A Windows Server 2003 computer that is running the Session Directory service.
  
  The Session Directory computer can be any Windows Server 2003-based computer that is visible on the network that is running the Terminal Services Session Directory service. As a best practice, the Session Directory server should be a highly available network server that is not running Terminal Services.

The following information describes the Terminal Server Connection Management process:

1. When the user logs on to the Terminal Server cluster, the terminal server that is receiving the initial client logon request sends a query to the Session Directory server.
2. The Session Directory server checks the user name against its database and sends the result to the requesting server.
3. If the user has no disconnected sessions, the logon process continues at the server that is hosting the initial connection.
4. If the user has a disconnected session on another server, the client session is passed to the second server and the logon process continues from that point.
5. When the user logs on to the disconnected session, the Session Directory is updated.