FIX: Error message when you run an application that makes "burst load" style activation requests and calls a server component through DCOM: "0x800706ba" or "0x800706bf"

When you run an application that makes a �burst load� style activation request that uses lots of threads, you receive one of the following error messages intermittently:

Error message 1Error message 2Error message 3This problem occurs if the following conditions are true:

• The application references a component on a remote computer through Distributed COM (DCOM).
• The application creates many threads at the same time.
• Each thread creates and then calls an instance of the component.

This problem occurs because the high rate of incoming requests exceeds the backlog queue limit that the AFD.SYS socket driver keeps. The AFD.SYS socket driver then rejects or closes the requests.

A supported hotfix is now available from Microsoft. However, it is intended to correct only the problem that is described in this article. Apply it only to systems that are experiencing this specific problem. This hotfix may receive additional testing. Therefore, if you are not severely affected by this problem, we recommend that you wait for the next service pack that contains this hotfix.

To resolve this problem immediately, contact Microsoft Customer Support Services to obtain the hotfix. For a complete list of Microsoft Customer Support Services telephone numbers and information about support costs, visit the following Microsoft Web site:Note In special cases, charges that are ordinarily incurred for support calls may be canceled if a Microsoft Support Professional determines that a specific update will resolve your problem. The usual support costs will apply to additional support questions and issues that do not qualify for the specific update in question.

Prerequisites

You must have Windows Server 2003 SP2 installed to apply this hotfix.

Restart requirement

You must restart the computer after you apply this hotfix.

Hotfix replacement information

This hotfix does not replace any other hotfixes.

Registry information

Important This section, method, or task contains steps that tell you how to modify the registry. However, serious problems might occur if you modify the registry incorrectly. Therefore, make sure that you follow these steps carefully. For added protection, back up the registry before you modify it. Then, you can restore the registry if a problem occurs. For more information about how to back up and restore the registry, click the following article number to view the article in the Microsoft Knowledge Base: After you install the hotfix, you must set the backlog queue length that the COM runtime passes to the TCP listen�function of the COM server by creating the following registry entry with REG_DWORD value: Notes

• The guid placeholder represents the application ID that is generated for the server process that must accept calls at a faster rate than the default setting allows.
• The default value for the RpcProtSeqMaxCalls registry entry is hex 0x0A or decimal 10. The maximum value is 0x64 or decimal 100.
• This registry setting only takes effect after you apply the hotfix that this article describes and after the computer is restarted.

Additionally, you may have to change the following registry entries to increase the dynamic backlog queue for the socket driver and set the backlog queue length:

• EnableDynamicBacklog
• MinimumDynamicBacklog
• MaximumDynamicBacklog
• DynamicBacklogGrowthDelta

The following are the recommended values for this registry entry.You can turn off the SynAttackProtect global key on the server. To do this, you must set the vaule of the following registry entry to 0x0:Note Turning off the SynAttackProtect global key is not required in this scenario.

For more information about how to set these registry keys, click the following article number to view the article in the Microsoft Knowledge Base:

File information

The English version of this hotfix has the file attributes (or later file attributes) that are listed in the following table. The dates and times for these files are listed in Coordinated Universal Time (UTC). When you view the file information, it is converted to local time. To find the difference between UTC and local time, use the Time Zone tab in the Date and Time item in Control Panel.

x86 version for Windows Server 2003

x64 version for Windows Server 2003

IA-64 version for Windows Server 2003

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

The AFD.SYS socket driver keeps a backlog queue of incoming RDP requests that a server application will accept. This queue is limited by the hardcoded input parameter to the listen function.

The COM runtime specifies the RPC_C_PROTSEQ_MAX_REQS_DEFAULT value for the MaxCalls parameter when the COM runtime calls the RpcServerUseProtseq APIs. The RPC_C_PROTSEQ_MAX_REQS_DEFAULT value in Windows Server 2003 is 10. RPC uses this value to specify the TCP backlog queue length of the socket when RPC calls the listen function. If the value is 10, clients start to see TCP resets and RPC errors from COM calls in an environment in which more than 10 clients connect to the same server at the same time. The hotfix allows for a COM application to specify the value that COM uses as the MaxCalls parameter to the RpcServerUseProtseq APIs.

Note This hotfix only applies to the ncacn_ip_tcp protocol.

For more information about the AppID key, visit the following Microsoft Developer Network (MSDN) Web site: For more information about how to harden the TCP/IP stack, visit the following MSDN Web site: