Microsoft KB Archive/260551

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DNS Resolver Requires Modification in Slow Link Networks

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Q260551

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The information in this article applies to:


 * Microsoft Windows NT Workstation version 4.0 SP4
 * Microsoft Windows NT Server version 4.0 SP4

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IMPORTANT: This article contains information about editing the registry. Before you edit the registry, make sure you understand how to restore it if a problem occurs. For information about how to do this, view the &quot;Restoring the Registry&quot; Help topic in Regedit.exe or the &quot;Restoring a Registry Key&quot; Help topic in Regedt32.exe.

SUMMARY
In Windows NT 4.0 Service Pack 4 (SP4), DNS Resolver (DNR) was changed to provide increased usability in local area networks (LAN) environments. This article explains how to modify the DNR change for high latency environments.

MORE INFORMATION
WARNING: Using Registry Editor incorrectly can cause serious problems that may require you to reinstall your operating system. Microsoft cannot guarantee that problems resulting from the incorrect use of Registry Editor can be solved. Use Registry Editor at your own risk.

For information about how to edit the registry, view the &quot;Changing Keys and Values&quot; Help topic in Registry Editor (Regedit.exe) or the &quot;Add and Delete Information in the Registry&quot; and &quot;Edit Registry Data&quot; Help topics in Regedt32.exe. Note that you should back up the registry before you edit it. If you are running Windows NT or Windows 2000, you should also update your Emergency Repair Disk (ERD).

NOTE: The settings described in this article should only be used in networks where DNS servers are on remote high latency links, for example, slow dial-up lines or satellite networks.

The change to the DNR that was initiated in Windows NT 4.0 SP4 can cause performance issues in high latency environments. For example, when the client sends multiple DNS queries before receiving the first response, the DNS servers are flooded. To avoid this issue, you can add a configurable timer on the DNR, which specifies how long the DNR waits before sending subsequent queries.

To add a configurable timer on the DNR, follow these steps:


 * 1) Start Registry Editor (Regedt32.exe).
 * 2) Locate and click the following key in the registry:
 * 3) On the Edit menu, click Add Value, and then add the following registry value:
 * 4) Quit Registry Editor.

The DNSQueryTimeouts registry setting determines how long the DNS client waits for a response to each of the five attempts that make up the name resolution process. If the time that is specified for any attempt elapses before DNS receives a response, DNS repeats the query.

The value of this setting is an ordered list of five time limits (in seconds). The sixth value, which must be a zero, indicates the end of the list. Each time limit is applied to the corresponding attempt in the name resolution process in the following order:

For additional information about the changes in the DNR, click the article number below to view the article in the Microsoft Knowledge Base:

"Q198550 SP4 Changes DNS Name Resolution" Additional query words:

Keywords :

Issue type :

Technology : kbWinNTsearch kbWinNTWsearch kbWinNTW400search kbWinNT400xsearch kbWinNTW400sp4 kbWinNTSsearch kbWinNTS400sp4 kbWinNTS400xsearch