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 1The remote procedure call failed and did not execute. (Exception from HRESULT: 0x800706BF)
The RPC server is unavailable. (Exception from HRESULT: 0x800706BA)
The remote procedure call failed. (Exception from HRESULT: 0x800706BE)
This 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:
322756Â
(http://kbalertz.com/Feedback.aspx?kbNumber=322756/
)
How to back up and restore the registry in Windows
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:
HKEY_CLASSES_ROOT\AppID\{guid}\RpcProtSeqMaxCalls
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:
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\AFD\Parameters
- EnableDynamicBacklog
- MinimumDynamicBacklog
- MaximumDynamicBacklog
- DynamicBacklogGrowthDelta
The following are the recommended values for this registry entry.
Collapse this tableExpand this table
| Value Name | Value (REG_DWORD) |
| EnableDynamicBacklog | 1 |
| MinimumDynamicBacklog | 20 |
| MaximumDynamicBacklog | 20000 |
| DynamicBacklogGrowthDelta | 10 |
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:
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters\SynAttackProtect
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:
142641Â
(http://kbalertz.com/Feedback.aspx?kbNumber=142641/
)
Internet server unavailable because of malicious SYN attacks
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
Collapse this tableExpand this table
| File name | File version | File size | Date | Time | Platform |
|---|
| Ole32.dll | 5.2.3790.4413 | 1,269,760 | 20-Nov- 2008 | 05:29 | x86 |
x64 version for Windows Server 2003
Collapse this tableExpand this table
| File name | File version | File size | Date | Time | Platform | SP requirement | Service branch |
|---|
| Ole32.dll | 5.2.3790.4413 | 2,626,048 | 20-Nov- 2008 | 03:33 | x64 | SP2 | SP2QFE |
| Wole32.dll | 5.2.3790.4413 | 1,269,760 | 2 0-Nov-2008 | 03:33 | x86 | SP2 | WOW |
IA-64 version for Windows Server 2003
Collapse this tableExpand this table
| File name | File version | File size | Date | Time | Platform | SP requirement | Service branch |
|---|
| Ole32.dll | 5.2.3790.4413 | 4,101,632 | 20-Nov- 2008 | 03:32 | IA- 64 | SP2 | SP2QFE |
| Wole32.dll | 5.2.3790.4413 | 1,269,760 | 20-Nov- 2008 | 03:32 | x86 | SP2 | WOW |
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: