Symptoms

Assume that you configure Windows Server 2008 Terminal Services Session Broker (TS Session Broker) by using DNS round robin. However, after some time, new sessions are redirected to only one server or to only a specific set of servers. This behavior occurs even though the load of other terminal servers on the network is low.

Additionally, after this problem occurs, events that resemble the following are logged in the session broker log (Tssdis.log):Note The Tssdis.log file is located in the %windir%\system32\tssesdir directory.

Cause

A pending redirection occurs when a new user logs on to the farm of terminal servers, and TS Session Broker points the user to a particular terminal server before the logon process has finished. The session directory tracks the number of pending redirections for each terminal server, and then it increases the count when the TS Session Broker determines the target server. Additionally, the session directory decreases the count after the logon process is complete.

However, the TS Session Broker service incorrectly increases the count of pending redirections for disconnected terminal sessions, and it never decreases the count. Therefore, when the pending redirection count on a terminal server reaches its limit (16, by default), the TS Session Broker service no longer redirects new terminal sessions to this terminal server. Eventually, the number of available servers decreases to a small set or to only a single server.

Resolution

Hotfix information

A supported hotfix is available from Microsoft. However, this hotfix is intended to correct only the problem that is described in this article. Apply this hotfix only to systems that are experiencing this specific problem. This hotfix might receive additional testing. Therefore, if you are not severely affected by this problem, we recommend that you wait for the next software update that contains this hotfix.

If the hotfix is available for download, there is a "Hotfix download available" section at the top of this Knowledge Base article. If this section does not appear, contact Microsoft Customer Service and Support to obtain the hotfix.

Note If additional issues occur or if any troubleshooting is required, you might have to create a separate service request. The usual support costs will apply to additional support questions and issues that do not qualify for this specific hotfix. For a complete list of Microsoft Customer Service and Support telephone numbers or to create a separate service request, visit the following Microsoft Web site:

http://support.microsoft.com/contactus/?ws=supportNote The "Hotfix download available" form displays the languages for which the hotfix is available. If you do not see your language, it is because a hotfix is not available for that language.

Important Windows Vista and Windows Server 2008 hotfixes are included in the same packages. However, only one of these products may be listed on the “Hotfix Request” page. To request the hotfix package that applies to both Windows Vista and Windows Server 2008, just select the product that is listed on the page.

Prerequisites

To apply this hotfix, you must have Windows Server 2008 TS Session Broker installed.

Restart requirement

You must restart the computer after you apply this hotfix.

Hotfix replacement information

This hotfix does not replace any other hotfixes.

File information

The English version of this hotfix has the file attributes (or later file attributes) that are listed in the following table. The dates and times for these files are listed in Coordinated Universal Time (UTC). When you view the file information, it is converted to local time. To find the difference between UTC and local time, use the Time Zone tab in the Date and Time item in Control Panel.

Windows Server 2008 file information notes

The MANIFEST files (.manifest) and MUM files (.mum) that are installed for each environment are listed separately. MUM and MANIFEST files, and the associated security catalog (.cat) files, are critical to maintaining the state of the updated component. The security catalog files (attributes not listed) are signed with a Microsoft digital signature.

For all supported x86-based versions of Windows Server 2008

File name

File version

File size

Date

Time

Platform

Terminalserversessiondirectoryrole.cmd

Not Applicable

243

18-Dec-2007

21:03

Not Applicable

Tssdis.exe

6.0.6001.22246

128,000

19-Aug-2008

03:30

x86

Tssessiondirectory.events.xml

Not Applicable

393

18-Dec-2007

21:03

Not Applicable

For all supported x64-based versions of Windows Server 2008

File name

File version

File size

Date

Time

Platform

Terminalserversessiondirectoryrole.cmd

Not Applicable

243

18-Dec-2007

21:03

Not Applicable

Tssdis.exe

6.0.6001.22246

157,184

19-Aug-2008

04:46

x64

Tssessiondirectory.events.xml

Not Applicable

393

18-Dec-2007

21:03

Not Applicable

Workaround

To work around this problem, use one of the following methods.

Method 1

Restart TS Session Broker. This may temporarily resolve the problem. However, this problem recurs after several days.

Method 2

  1. Click Start, click Run, type regedit in the Open box, and then press ENTER.

  2. In Registry Editor, locate and then click the following registry subkey:

    HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tssdis\Parameters

  3. In the details pane, double-click
    LB_MaxNumberOfPendingRedirections.

    Note If the LB_MaxNumberOfPendingRedirections DWORD entry does not exist, you must create it. To do this, follow these steps:

    1. In Registry Editor, locate and then click the following registry subkey:

      HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tssdis\Parameters

    2. On the Edit menu, point to
      New, and then click DWORD Value.

    3. Type
      LB_MaxNumberOfPendingRedirections, and then press ENTER.

  4. In the Value data box, type a number that is much larger than 16 (but less than 65535), and then click OK.

  5. Exit Registry Editor

Important This method may have the following serious consequences:

  • It may overload a terminal server with logon requests.

  • It may disrupt or disable the network's load-balancing.

Status

Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.

More Information

For more information about TS Session Broker, visit the following Microsoft Web site:

http://technet.microsoft.com/en-us/library/cc731045.aspxTo enable TS Session Broker logging, follow these steps:

  1. Stop the TS Session Broker service.

  2. In Registry Editor, locate the following registry subkey:

    HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tssdis\Parameters

  3. Create the TraceOutputMode DWORD registry entry, and then set its value to 3.

  4. Start the TS Session Broker service.

Additional file information for Windows Server 2008

Additional files for all supported x86-based versions of Windows Server 2008

File name

Package_1_for_kb955365~31bf3856ad364e35~x86~~6.0.1.0.mum

File version

Not Applicable

File size

1,820

Date (UTC)

19-Aug-2008

Time (UTC)

22:55

Platform

Not Applicable

File name

Package_for_kb955365_server_0~31bf3856ad364e35~x86~~6.0.1.0.mum

File version

Not Applicable

File size

1,432

Date (UTC)

19-Aug-2008

Time (UTC)

22:55

Platform

Not Applicable

File name

Package_for_kb955365_server~31bf3856ad364e35~x86~~6.0.1.0.mum

File version

Not Applicable

File size

1,430

Date (UTC)

19-Aug-2008

Time (UTC)

22:55

Platform

Not Applicable

File name

X86_07684ecbb7d7638c937ffee6b2b248ba_31bf3856ad364e35_6.0.6001.22246_none_6e8705284fb7f98b.manifest

File version

Not Applicable

File size

728

Date (UTC)

19-Aug-2008

Time (UTC)

22:55

Platform

Not Applicable

File name

X86_microsoft-windows-t..iondirectory-server_31bf3856ad364e35_6.0.6001.22246_none_f3e0ce92ec5ca9a3.manifest

File version

Not Applicable

File size

31,695

Date (UTC)

19-Aug-2008

Time (UTC)

04:06

Platform

Not Applicable

Additional files for all supported x64-based versions of Windows Server 2008

File name

Amd64_f22e3df22c71dd9c356ec74170560805_31bf3856ad364e35_6.0.6001.22246_none_effc862e5acbbdf8.manifest

File version

Not Applicable

File size

732

Date (UTC)

19-Aug-2008

Time (UTC)

22:55

Platform

Not Applicable

File name

Amd64_microsoft-windows-t..iondirectory-server_31bf3856ad364e35_6.0.6001.22246_none_4fff6a16a4ba1ad9.manifest

File version

Not Applicable

File size

31,731

Date (UTC)

19-Aug-2008

Time (UTC)

05:30

Platform

Not Applicable

File name

Package_1_for_kb955365~31bf3856ad364e35~amd64~~6.0.1.0.mum

File version

Not Applicable

File size

1,830

Date (UTC)

19-Aug-2008

Time (UTC)

22:55

Platform

Not Applicable

File name

Package_for_kb955365_server_0~31bf3856ad364e35~amd64~~6.0.1.0.mum

File version

Not Applicable

File size

1,440

Date (UTC)

19-Aug-2008

Time (UTC)

22:55

Platform

Not Applicable

File name

Package_for_kb955365_server~31bf3856ad364e35~amd64~~6.0.1.0.mum

File version

Not Applicable

File size

1,438

Date (UTC)

19-Aug-2008

Time (UTC)

22:55

Platform

Not Applicable

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