How to use the throttling mechanism to control network performance in Windows Vista

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Article ID: 948066 - View products that this article applies to.
Important This article contains information about how to modify the registry. Make sure that you back up the registry before you modify it. Make sure that you know how to restore the registry if a problem occurs. For more information about how to back up, restore, and modify the registry, click the following article number to view the article in the Microsoft Knowledge Base:
322756 How to back up and restore the registry in Windows XP and Windows Vista
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INTRODUCTION

This article describes how to use network throttling to control network performance on a computer that is running Windows Vista.

MORE INFORMATION

Multimedia traffic

The processing of network packets on a computer is a resource-intensive task. On high bandwidth links, network traffic consumes even more system resources. Additionally, multimedia programs are time sensitive, and such programs require prioritized access to CPU resources.

For more information about processing that is prioritized for multimedia programs, visit the following Microsoft Developers Network Web site:
http://msdn2.microsoft.com/en-us/library/ms684247(VS.85)

Windows throttling mechanism

Because multimedia programs require more resources, the Windows networking stack implements a throttling mechanism to restrict the processing of non-multimedia network traffic to 10 packets per millisecond.

The throttling will come into effect only when you are running multimedia programs that are time sensitive. However, this throttling mechanism can potentially cause a decrease in network performance during the active multimedia playback period. This decrease in performance is likely to occur only on high speed networks that are saturated to maximum capacity.

How to improve network performance in Windows Vista

Warning Serious problems might occur if you modify the registry incorrectly by using Registry Editor or by using another method. These problems might require that you reinstall the operating system. Microsoft cannot guarantee that these problems can be solved. Modify the registry at your own risk.

In circumstances where you experience a decrease in network performance, you can control the throttling rate to improve network performance in Windows Vista. However, you must do this with caution because this may affect the quality of multimedia playback.

To configure the throttling rate, change the value of the NetworkThrottlingIndex registry entry under the following registry subkey:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Multimedia\SystemProfile\

Name : NetworkThrottlingIndex
Value type : DWORD
Value data : From integer 1 through integer 70 (Decimal) (Decimal)

By default, the value for the NetworkThrottlingIndex registry entry is set to 10. When the NetworkThrottlingIndex registry entry does not exist, the behavior resembles the default behavior. Network throttling can be completely turned off by setting the value to FFFFFFFF (hexadecimal). You must restart the computer after you make a change to the value of the NetworkThrottlingIndex registry entry.

Important The default value is unlikely to cause degradation in network performance in most common Internet usage scenarios that use broadband connections. We recommend that you only use the throttling mechanism after you fully understand the tradeoff between multimedia playback quality and network performance.

Properties

Article ID: 948066 - Last Review: February 21, 2008 - Revision: 1.1
APPLIES TO
  • Windows Vista Service Pack 1
Keywords: 
kbinfo kbperformance kbnetwork_generalbroadband kbnetwork_latencyperformance kbexpertiseadvanced kbhowto KB948066

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