The SACK option is always set to "true" even if network adapter does not support SACK for offloaded connections in Windows 7 or in Windows Server 2008 R2

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Article ID: 2525390 - View products that this article applies to.
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SYMPTOMS

Consider the following scenario:
  • You enable the TCP/IP Offloading feature on a computer that is running Windows 7 or Windows Server 2008 R2.
  • You have a TCP Offloading capable network adapter installed on the computer.
  • The network adapter does not support the Selective Acknowledgements (SACK) option.
In this scenario, the TCP SACK option is always set to "true" for offloaded TCP connections on the network adapter. This behavior causes poor performance in busy network environments.

RESOLUTION

After you install this hotfix, the SACK option is automatically disabled if the following conditions are true:
  • The TCP Offloading feature is enabled.
  • You install a TCP offloading capable network adapter on the computer and keep it active.

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=support
Note 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 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 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 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.
    Collapse this tableExpand this table
    VersionProductSR_LevelService branch
    6.1.760 0 . 20xxxWindows 7 and Windows Server 2008 R2RTMLDR
    6.1.760 1 . 21xxxWindows 7 and Windows Server 2008 R2SP1LDR
  • 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
Collapse this tableExpand this table
File nameFile versionFile sizeDateTimePlatform
Fwpkclnt.sys6.1.7600.20929187,26421-Mar-201104:44x86
Tcpip.sys6.1.7600.209291,298,81621-Mar-201104:44x86
Fwpkclnt.sys6.1.7601.21687187,77619-Mar-201106:58x86
Tcpip.sys6.1.7601.216871,300,86419-Mar-201106:58x86
For all supported x64-based versions of Windows 7 and of Windows Server 2008 R2
Collapse this tableExpand this table
File nameFile versionFile sizeDateTimePlatform
Fwpkclnt.sys6.1.7600.20929288,12821-Mar-201105:35x64
Tcpip.sys6.1.7600.209291,893,24821-Mar-201105:36x64
Fwpkclnt.sys6.1.7601.21687288,64019-Mar-201107:45x64
Tcpip.sys6.1.7601.216871,927,55219-Mar-201107:45x64
For all supported IA-64-based versions of Windows Server 2008 R2
Collapse this tableExpand this table
File nameFile versionFile sizeDateTimePlatform
Fwpkclnt.sys6.1.7600.20929482,68821-Mar-201104:11IA-64
Tcpip.sys6.1.7600.209293,804,03221-Mar-201104:12IA-64
Fwpkclnt.sys6.1.7601.21687483,20019-Mar-201106:50IA-64
Tcpip.sys6.1.7601.216873,807,61619-Mar-201106:50IA-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
For more information about Windows TCP features, click the following article number to view the article in the Microsoft Knowledge Base:
224829 Description of Windows 2000 and Windows Server 2003 TCP Features
For more information about TCP Selective Acknowledgment options, visit the following Microsoft website:For more information about how to use TCP chimney offload, click the following Microsoft Developer Network (MSDN) website:
General information about how to use TCP Chimney Offload

Note You cannot disable Selective Acknowledgements (SACK) in Windows 7 or in Windows Server 2008 R2 unless both of the following prerequisites are met:
  • You have a network adapter that can perform TCP chimney offloading.
  • You have installed the hotfix that is described in Microsoft Knowledge Base (KB) article 2525390.
Additionally, you cannot disable SACK by using the SackOpts registry key in Windows 7 or in Windows Server 2008 R2.

Additional file information

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

Additional files for all supported x86-based versions of Windows 7
Collapse this tableExpand this table
File nameUpdate.mum
File versionNot applicable
File size2,773
Date (UTC)22-Mar-2011
Time (UTC)02:07
PlatformNot applicable
File nameX86_0512aa0464bfc19a711aba1be57414e3_31bf3856ad364e35_6.1.7601.21687_none_866f98539b510090.manifest
File versionNot applicable
File size702
Date (UTC)22-Mar-2011
Time (UTC)02:07
PlatformNot applicable
File nameX86_1f2b73c4a0acdc952650bed1a1d7781b_31bf3856ad364e35_6.1.7600.20929_none_d817d3f48b37e5b1.manifest
File versionNot applicable
File size702
Date (UTC)22-Mar-2011
Time (UTC)02:07
PlatformNot applicable
File nameX86_microsoft-windows-tcpip-binaries_31bf3856ad364e35_6.1.7600.20929_none_b3c2ef6ee0a325aa.manifest
File versionNot applicable
File size3,834
Date (UTC)21-Mar-2011
Time (UTC)05:13
PlatformNot applicable
File nameX86_microsoft-windows-tcpip-binaries_31bf3856ad364e35_6.1.7601.21687_none_b5666a72ddfc0967.manifest
File versionNot applicable
File size3,834
Date (UTC)19-Mar-2011
Time (UTC)07:23
PlatformNot applicable
Additional files for all supported x64-based versions of Windows 7 and of Windows Server 2008 R2
Collapse this tableExpand this table
File nameAmd64_51400f4928afb5a68a25eddbc206ab09_31bf3856ad364e35_6.1.7601.21687_none_9fa0325151e075f8.manifest
File versionNot applicable
File size706
Date (UTC)22-Mar-2011
Time (UTC)02:07
PlatformNot applicable
File nameAmd64_e659707d62cacf300cb4f2a75472edda_31bf3856ad364e35_6.1.7600.20929_none_7711d76b14d02b43.manifest
File versionNot applicable
File size706
Date (UTC)22-Mar-2011
Time (UTC)02:07
PlatformNot applicable
File nameAmd64_microsoft-windows-tcpip-binaries_31bf3856ad364e35_6.1.7600.20929_none_0fe18af2990096e0.manifest
File versionNot applicable
File size3,838
Date (UTC)21-Mar-2011
Time (UTC)06:11
PlatformNot applicable
File nameAmd64_microsoft-windows-tcpip-binaries_31bf3856ad364e35_6.1.7601.21687_none_118505f696597a9d.manifest
File versionNot applicable
File size3,838
Date (UTC)19-Mar-2011
Time (UTC)08:17
PlatformNot applicable
File nameUpdate.mum
File versionNot applicable
File size3,215
Date (UTC)22-Mar-2011
Time (UTC)02:07
PlatformNot applicable
Additional files for all supported IA-64-based versions of Windows Server 2008 R2
Collapse this tableExpand this table
File nameIa64_68c1920b5e2460f5ecb8b4c8f4eca74a_31bf3856ad364e35_6.1.7600.20929_none_f1e5b4a54365fa8f.manifest
File versionNot applicable
File size704
Date (UTC)22-Mar-2011
Time (UTC)02:07
PlatformNot applicable
File nameIa64_856d75fc2dc29c51020ca7b136fbfd9f_31bf3856ad364e35_6.1.7601.21687_none_e94e75040f4aeed1.manifest
File versionNot applicable
File size704
Date (UTC)22-Mar-2011
Time (UTC)02:07
PlatformNot applicable
File nameIa64_microsoft-windows-tcpip-binaries_31bf3856ad364e35_6.1.7600.20929_none_b3c49364e0a12ea6.manifest
File versionNot applicable
File size3,836
Date (UTC)21-Mar-2011
Time (UTC)06:06
PlatformNot applicable
File nameIa64_microsoft-windows-tcpip-binaries_31bf3856ad364e35_6.1.7601.21687_none_b5680e68ddfa1263.manifest
File versionNot applicable
File size3,836
Date (UTC)19-Mar-2011
Time (UTC)08:19
PlatformNot applicable
File nameUpdate.mum
File versionNot applicable
File size2,168
Date (UTC)22-Mar-2011
Time (UTC)02:07
PlatformNot applicable

Properties

Article ID: 2525390 - Last Review: March 6, 2012 - Revision: 6.0
APPLIES TO
  • Windows Server 2008 R2 Datacenter
  • Windows Server 2008 R2 Enterprise
  • Windows Server 2008 R2 for Itanium-Based Systems
  • Windows Server 2008 R2 Foundation
  • Windows Server 2008 R2 Standard
  • Windows 7 Enterprise
  • Windows 7 Home Basic
  • Windows 7 Home Premium
  • Windows 7 Professional
  • Windows 7 Starter
  • Windows 7 Ultimate
Keywords: 
kbautohotfix kbqfe kbhotfixserver kbfix kbexpertiseadvanced kbexpertiseinter kbsurveynew KB2525390

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