Microsoft KB Archive/246118

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How to configure your IAS server for a very large number of authentication requests

Article ID: 246118

Article Last Modified on 7/26/2007


  • Microsoft Windows 2000 Server
  • Microsoft Windows 2000 Advanced Server
  • Microsoft Windows 2000 Datacenter Server

This article was previously published under Q246118

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:

256986 Description of the Microsoft Windows registry


This step-by-step article describes how to improve authentication throughput on your Internet Authentication Server (IAS) computer.

If the IAS server receives a very large number of authentication requests per second, you can improve throughput by increasing the number of concurrent authentication calls that are in progress at one time between the IAS server and the domain controller.

Add a registry key

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.

Follow these steps to increase the number of concurrent authentication calls in progress at one time between the IAS server and the domain controller:

  1. Start Registry Editor. To do this, click Start, click Run, type Regedt32.exe, and then click OK.
  2. Locate the following registry key:


  3. On the Edit menu, click Add Value, and then add the following registry information (where 10 represents the heaviest loads):

    Value Name: MaxConcurrentApi
    Data Type: REG_DWORD
    Value: between 0 and 10
  4. Restart the NETLOGON service.

Note If the value that you assign to MaxConcurrentAPI is too high, the IAS server might put a heavy load on the domain controller.

If you have a computer that is running Microsoft Windows 2000 Advanced Server, you can use the Network Load Balancing component (previously known as WLBS) of Windows 2000 Advanced Server to distribute incoming access requests among multiple IAS servers. This helps your server perform better when network traffic is high.


For more information about Microsoft Internet Security and Acceleration (ISA) Server, click the following article numbers to view the articles in the Microsoft Knowledge Base:

326040 How to configure your ISA Server for a very large number of authentication requests

Keywords: kbenv kbhowtomaster kbnetwork KB246118