Applications can't communicate over TCP loopback path in Windows 8.1 or Windows Server 2012 R2

This article describes an issue that blocks communication over a TCP loopback path for applications in Windows 8.1, Windows RT 8.1, or Windows Server 2012 R2. An update is available to fix this issue. Before you install this update, see the Prerequisites section.

Symptoms

When this issue occurs, the loopback TCP packets fall from a fast path to a slow path and are then dropped. 

Cause

This issue occurs because of an incorrect checksum.

Hotfix information

Important If you install a language pack after you install this hotfix, you must reinstall this hotfix. Therefore, we recommend that you install any language packs that you need before you install this hotfix. For more information, see Add language packs to Windows.


A supported hotfix is available from Microsoft. However, this hotfix is intended to correct only the problem that's described in this article. Apply this hotfix only to systems that are experiencing this specific problem.

If the hotfix is available for download, there's a "Hotfix Download Available" section at the top of this Knowledge Base article. If this section doesn't appear, submit a request to Microsoft Customer Service and Support to get 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 don't 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 website:

http://support.microsoft.com/contactus/?ws=supportNote The "Hotfix Download Available" form displays the languages for which the hotfix is available. If you don't see your language, it's because a hotfix isn't available for that language.

Prerequisites

To apply this hotfix, install update 2919355 in Windows 8.1 or Windows Server 2012 R2.

Registry information

To use the hotfix in this package, you don't have to make any changes to the registry.

Restart requirement

You may have to restart the computer after you apply this hotfix.

Hotfix replacement information

This hotfix doesn't replace a previously released hotfix.

Status

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

References

Learn about the terminology that Microsoft uses to describe software updates.

File information

The English (United States) version of this software update installs files that have the attributes that are listed in the following tables. The dates and times for these files are listed in Coordinated Universal Time (UTC). Be aware that dates and times for these files on your local computer are displayed in your local time and with your current daylight saving time bias. The dates and times may also change when you perform certain operations on the files.

Notes

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

    Version

    Product

    Milestone

    Service branch

    6.3.960 0.17 xxx

    Windows RT 8.1, Windows 8.1, and Windows Server 2012 R2

    RTM

    GDR

    6.3.960 0.18 xxx

    Windows RT 8.1, Windows 8.1, and Windows Server 2012 R2

    RTM

    GDR

  • GDR service branches contain only those fixes that are widely released to address widespread, critical issues. LDR service branches contain hotfixes in addition to widely released fixes.

  • The MANIFEST files (.manifest) and the MUM files (.mum) that are installed for each environment are listed in the "Additional file information" section. MUM, MANIFEST, and the associated security catalog (.cat) files, are very 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.

Windows RT 8.1

File name

File version

File size

Date

Time

Platform

Fwpkclnt.sys

6.3.9600.17336

278,864

08-Sep-2014

01:20

Not applicable

Tcpip.sys

6.3.9600.18124

1,759,592

10-Nov-2015

06:12

Not applicable

x64 Windows 8.1 and Windows Server 2012 R2

File name

File version

File size

Date

Time

Platform

Fwpkclnt.sys

6.3.9600.17903

428,888

11-Jun-2015

20:12

x64

Tcpip.sys

6.3.9600.18124

2,474,840

10-Nov-2015

06:01

x64

x86 Windows 8.1

File name

File version

File size

Date

Time

Platform

Fwpkclnt.sys

6.3.9600.17485

286,528

10-Nov-2014

17:47

x86

Tcpip.sys

6.3.9600.18124

1,852,248

10-Nov-2015

06:06

x86


Windows RT 8.1

File property

Value

File name

Arm_497393c0c4a1ee39545723a197b955ad_31bf3856ad364e35_6.3.9600.18124_none_512fafa6916ff48e.manifest

File version

Not applicable

File size

702

Date (UTC)

11-Nov-2015

Time (UTC)

00:25

Platform

Not applicable

File name

Arm_microsoft-windows-tcpip-binaries_31bf3856ad364e35_6.3.9600.18124_none_4800f75d81cc8648.manifest

File version

Not applicable

File size

3,883

Date (UTC)

11-Nov-2015

Time (UTC)

00:25

Platform

Not applicable

File name

Update.mum

File version

Not applicable

File size

1,610

Date (UTC)

11-Nov-2015

Time (UTC)

00:25

Platform

Not applicable

x64 Windows 8.1 and Windows Server 2012 R2

File property

Value

File name

Amd64_00d951a165807255209f869bece77e12_31bf3856ad364e35_6.3.9600.18124_none_6b84df93eb7c11b3.manifest

File version

Not applicable

File size

706

Date (UTC)

11-Nov-2015

Time (UTC)

00:25

Platform

Not applicable

File name

Amd64_microsoft-windows-tcpip-binaries_31bf3856ad364e35_6.3.9600.18124_none_a41d20893a2cd8b8.manifest

File version

Not applicable

File size

3,887

Date (UTC)

11-Nov-2015

Time (UTC)

00:32

Platform

Not applicable

File name

Update.mum

File version

Not applicable

File size

1,618

Date (UTC)

11-Nov-2015

Time (UTC)

00:25

Platform

Not applicable

x86 Windows 8.1

File property

Value

File name

Update.mum

File version

Not applicable

File size

1,610

Date (UTC)

11-Nov-2015

Time (UTC)

00:25

Platform

Not applicable

File name

X86_d6c0173338a38ab3028693cdeb17eeb4_31bf3856ad364e35_6.3.9600.18124_none_3bae2a1bd68efb0b.manifest

File version

Not applicable

File size

702

Date (UTC)

11-Nov-2015

Time (UTC)

00:25

Platform

Not applicable

File name

X86_microsoft-windows-tcpip-binaries_31bf3856ad364e35_6.3.9600.18124_none_47fe850581cf6782.manifest

File version

Not applicable

File size

3,883

Date (UTC)

11-Nov-2015

Time (UTC)

00:29

Platform

Not applicable


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