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Throttle network adapters

How to limit the bandwidth used by a system, or a specific adapter.

Throttle network adapters
Serdar Yegulalp

When the network gets really busy, you may want to limit the bandwidth that a particular system or network adapter is using. This might be, for example, to save some network bandwidth for other connected systems. For whatever reason, you can do it with Windows 2000 servers, and today's administration tip tells you how you can accomplish it. It's done by a registry hack, though, so make sure you have the registry backed up just in case you mess up.

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Many programs (such as IIS) have some provision for limiting bandwidth consumption, but unless you're funneling all bandwidth through a proxy server, it's often hard to limit all the bandwidth used by a given Windows 2000 computer or network adapter.

There is a more global solution to the problem that doesn't involve a third-party program or tediously configuring every application that uses the network. It's a Registry edit. However, it requires the presence of the Quality of Service (QoS) Packet Scheduler driver in the network stack to be effective.

If you don't know about the QoS Packet Scheduler, chances are it was installed by default when you set your system up. It's an element of the Windows 2000 network stack that requires specific application support to use it, but which can be used to limit total throughput on a given adapter.

To do this for the whole system, regardless of adapters, open up RegEdit and find the key HKEY_LOCAL_MACHINESOFTWAREPoliciesMicrosoftWindowsPsched. Insert a new REG_DWORD value, NonBestEffortLimit, and for its parameter supply a number between 0 and 100 (decimal). The number indicates the total percentage of bandwidth to use. By default it's 20 percent, so if you want to rack it down even further than that, you can do so. (If there is no Psched key under Windows, feel free to create it.)

To set this value for a particular adapter, navigate to HKEY_LOCAL_MACHINESYSTEMCurrentControlSetServicesPschedParametersAdapters[GUID], where [GUID] is the GUID number of the adapter you want to set limits on, and add the NonBestEffortLimit value there.

Serdar Yegulalp is the editor of the Windows 2000 Power Users Newsletter.

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Related Book

Windows 2000 Registry Little Black Book, Second Edition
by Nathan Wallace and Anthony Sequeira
Online Price: $29.99
Publisher Name: Coriolis Group
Date published: May 2001
This book is a concise and portable guide to configuration changes that can be made to Windows 2000 to aid in the administration of the operating system and improve performance and stability. The book has been revised and updated from the successful first edition based on actual Windows 2000 implementations.

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