Symptoms

When you run an application or service that accesses a remote Server Message Block (SMB)/Common Internet File System (CIFS) server, the number of CIFS sessions keeps increasing.

This issue occurs on a computer that is running one of the following operating systems:

  • Windows Vista

  • Windows Server 2008

  • Windows 7

  • Windows Server 2008 R2

When the resources are exhausted, the remote SMB/CIFS server does not respond to client requests.

Cause

This issue occurs because the Distributed File System (DFS) Namespace Client Driver (Dfsc.sys) does not release CIFS sessions correctly if a pre-existing server connection exists.

For example, a named pipe connection to the file server is a pre-existing server connection.

When another connection maps and unmaps a drive, or when another connection opens and closes the network location, this issue occurs if a named pipe connection exists.

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 the problem described in this article. 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.

Prerequisites

To apply this hotfix, you must be running one of the following operating systems:

  • Windows Vista Service Pack 2 (SP2)

  • Windows Server 2008 Service Pack 2 (SP2)

  • Windows 7

  • Windows 7 Service Pack 1 (SP1)

  • Windows Server 2008 R2

  • Windows Server 2008 R2 Service Pack 1 (SP1)

For more information about how to obtain a Windows Vista service pack, click the following article number to view the article in the Microsoft Knowledge Base:

935791 How to obtain the latest Windows Vista service pack

For more information about how to obtain a Windows Server 2008 service pack, click the following article number to view the article in the Microsoft Knowledge Base:

968849 How to obtain the latest service pack for Windows Server 2008

For more information about how to obtain a Windows 7 or a Windows Server 2008 R2 service pack, click the following article number to view the article in the Microsoft Knowledge Base:

976932 Information about Service Pack 1 for Windows 7 and for Windows Server 2008 R2

Registry information

To use the hotfix in this package, you do not have to make any changes to the registry.

Restart requirement

You must restart the computer after you apply this hotfix.

Hotfix replacement information

This hotfix does not replace a previously released hotfix.

File information

The global version of this hotfix installs files that have the attributes that are listed in the following tables. The dates and the times for these files are listed in Coordinated Universal Time (UTC). The dates and the times for these files on your local computer are displayed in your local time together with your current daylight saving time (DST) bias. Additionally, the dates and the times may change when you perform certain operations on the files.

Windows Vista and Windows Server 2008 file information notes

Important Windows Vista hotfixes and Windows Server 2008 hotfixes are included in the same packages. However, only "Windows Vista" is listed on the Hotfix Request page. To request the hotfix package that applies to one or both operating systems, select the hotfix that is listed under "Windows Vista" on the page. Always refer to the "Applies To" section in articles to determine the actual operating system that each hotfix applies to.

  • The files that apply to a specific product, SR_Level (RTM, SPn), and service branch (LDR, GDR) can be identified by examining the file version numbers as shown in the following table.

    Version

    Product

    SR_Level

    Service branch

    6.0.600
    2.
    22xxx

    Windows Vista and Windows Server 2008

    SP2

    LDR

  • The MANIFEST files (.manifest) and the MUM files (.mum) that are installed for each environment are listed separately in the "Additional file information for Windows Server 2008 and for Windows Vista" section. MUM files and MANIFEST files, and the associated security catalog (.cat) files, are extremely important to maintain the state of the updated components. The security catalog files, for which the attributes are not listed, are signed with a Microsoft digital signature.

For all supported x86-based versions of Windows Server 2008 and of Windows Vista

File name

File version

File size

Date

Time

Platform

Dfsc.sys

6.0.6002.22625

75,264

14-Apr-2011

14:36

x86

For all supported x64-based versions of Windows Server 2008 and of Windows Vista

File name

File version

File size

Date

Time

Platform

Dfsc.sys

6.0.6002.22625

97,792

14-Apr-2011

14:57

x64

For all supported IA-64–based versions of Windows Server 2008

File name

File version

File size

Date

Time

Platform

Dfsc.sys

6.0.6002.22625

238,592

14-Apr-2011

14:49

IA-64

Windows 7 and Windows Server 2008 R2 file information notes


Important Windows 7 hotfixes and Windows Server 2008 R2 hotfixes are included in the same packages. However, hotfixes on the Hotfix Request page are listed under both operating systems. To request the hotfix package that applies to one or both operating systems, select the hotfix that is listed under "Windows 7/Windows Server 2008 R2" on the page. Always refer to the "Applies To" section in articles to determine the actual operating system that each hotfix applies to.

  • The files that apply to a specific product, SR_Level (RTM, SPn), and service branch (LDR, GDR) can be identified by examining the file version numbers as shown in the following table.

    Version

    Product

    SR_Level

    Service branch

    6.1.760
    0.
    20xxx

    Windows 7 and Windows Server 2008 R2

    RTM

    LDR

    6.1.760
    1.
    21xxx

    Windows 7 and Windows Server 2008 R2

    SP1

    LDR

  • The MANIFEST files (.manifest) and the MUM files (.mum) that are installed for each environment are listed separately in the "Additional file information for Windows Server 2008 R2 and for Windows 7" section. MUM and MANIFEST files, and the associated security catalog (.cat) files, are extremely important to maintain the state of the updated components. The security catalog files, for which the attributes are not listed, are signed with a Microsoft digital signature.

For all supported x86-based versions of Windows 7

File name

File version

File size

Date

Time

Platform

Dfsc.sys

6.1.7600.20986

78,336

15-Jun-2011

06:45

x86

Dfsc.sys

6.1.7601.21747

78,336

15-Jun-2011

06:38

x86

For all supported x64-based versions of Windows 7 and of Windows Server 2008 R2

File name

File version

File size

Date

Time

Platform

Dfsc.sys

6.1.7600.20986

102,400

15-Jun-2011

07:08

x64

Dfsc.sys

6.1.7601.21747

102,400

15-Jun-2011

06:56

x64

For all supported IA-64-based versions of Windows Server 2008 R2

File name

File version

File size

Date

Time

Platform

Dfsc.sys

6.1.7600.20986

247,296

15-Jun-2011

06:29

IA-64

Dfsc.sys

6.1.7601.21747

247,296

15-Jun-2011

06:16

IA-64

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 software update terminology, click the following article number to view the article in the Microsoft Knowledge Base:

824684 Description of the standard terminology that is used to describe Microsoft software updates

Additional file information

Additional file information for Windows Vista and for Windows Server 2008

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

File name

Update.mum

File version

Not applicable

File size

3,078

Date (UTC)

14-Apr-2011

Time (UTC)

19:19

Platform

Not applicable

File name

X86_606e964c74b13aae543b35557c3795b1_31bf3856ad364e35_6.0.6002.22625_none_a8083a3ea80b4c56.manifest

File version

Not applicable

File size

697

Date (UTC)

14-Apr-2011

Time (UTC)

19:19

Platform

Not applicable

File name

X86_microsoft-windows-dfsclient_31bf3856ad364e35_6.0.6002.22625_none_89f9ad5afc6b7999.manifest

File version

Not applicable

File size

10,277

Date (UTC)

14-Apr-2011

Time (UTC)

17:07

Platform

Not applicable

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

File name

Amd64_0a5240e86011fb2c0c621eac8545ada9_31bf3856ad364e35_6.0.6002.22625_none_5be6b758050bc52c.manifest

File version

Not applicable

File size

701

Date (UTC)

14-Apr-2011

Time (UTC)

19:19

Platform

Not applicable

File name

Amd64_microsoft-windows-dfsclient_31bf3856ad364e35_6.0.6002.22625_none_e61848deb4c8eacf.manifest

File version

Not applicable

File size

10,538

Date (UTC)

14-Apr-2011

Time (UTC)

17:13

Platform

Not applicable

File name

Update.mum

File version

Not applicable

File size

3,102

Date (UTC)

14-Apr-2011

Time (UTC)

19:19

Platform

Not applicable

Additional files for all supported IA-64–based versions of Windows Server 2008

File name

Ia64_2eb723c922bed3d306faaf31e0236901_31bf3856ad364e35_6.0.6002.22625_none_9269d3a140b135c6.manifest

File version

Not applicable

File size

699

Date (UTC)

14-Apr-2011

Time (UTC)

19:19

Platform

Not applicable

File name

Ia64_microsoft-windows-dfsclient_31bf3856ad364e35_6.0.6002.22625_none_89fb5150fc698295.manifest

File version

Not applicable

File size

10,532

Date (UTC)

14-Apr-2011

Time (UTC)

16:59

Platform

Not applicable

File name

Update.mum

File version

Not applicable

File size

2,255

Date (UTC)

14-Apr-2011

Time (UTC)

19:19

Platform

Not applicable

Additional file information for Windows 7 and for Windows Server 2008 R2

Additional files for all supported x86-based versions of Windows 7

File name

Update.mum

File version

Not Applicable

File size

2,773

Date (UTC)

15-Jun-2011

Time (UTC)

13:45

Platform

Not Applicable

File name

X86_microsoft-windows-dfsclient_31bf3856ad364e35_6.1.7600.20986_none_87fb2a94608c2533.manifest

File version

Not Applicable

File size

8,646

Date (UTC)

15-Jun-2011

Time (UTC)

09:17

Platform

Not Applicable

File name

X86_microsoft-windows-dfsclient_31bf3856ad364e35_6.1.7601.21747_none_8a0dc7945d913ab2.manifest

File version

Not Applicable

File size

8,646

Date (UTC)

15-Jun-2011

Time (UTC)

09:16

Platform

Not Applicable

Additional files for all supported x64-based versions of Windows 7 and of Windows Server 2008 R2

File name

Amd64_microsoft-windows-dfsclient_31bf3856ad364e35_6.1.7600.20986_none_e419c61818e99669.manifest

File version

Not Applicable

File size

8,648

Date (UTC)

15-Jun-2011

Time (UTC)

10:21

Platform

Not Applicable

File name

Amd64_microsoft-windows-dfsclient_31bf3856ad364e35_6.1.7601.21747_none_e62c631815eeabe8.manifest

File version

Not Applicable

File size

8,648

Date (UTC)

15-Jun-2011

Time (UTC)

10:16

Platform

Not Applicable

File name

Update.mum

File version

Not Applicable

File size

3,215

Date (UTC)

15-Jun-2011

Time (UTC)

13:46

Platform

Not Applicable

Additional files for all supported IA-64-based versions of Windows Server 2008 R2

File name

Ia64_microsoft-windows-dfsclient_31bf3856ad364e35_6.1.7600.20986_none_87fcce8a608a2e2f.manifest

File version

Not Applicable

File size

8,647

Date (UTC)

15-Jun-2011

Time (UTC)

10:16

Platform

Not Applicable

File name

Ia64_microsoft-windows-dfsclient_31bf3856ad364e35_6.1.7601.21747_none_8a0f6b8a5d8f43ae.manifest

File version

Not Applicable

File size

8,647

Date (UTC)

15-Jun-2011

Time (UTC)

10:05

Platform

Not Applicable

File name

Update.mum

File version

Not Applicable

File size

2,168

Date (UTC)

15-Jun-2011

Time (UTC)

13:45

Platform

Not Applicable

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