Third-party networking applications or corporate proxies that function as layered service providers (LSPs) may interfere with Desktop Passthrough (DTPT) traffic for Microsoft ActiveSync 4.x and for Windows Mobile Device Center (WMDC). Examples of LSPs are parental controls, the ISA proxy, and even some firewalls.
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
Problems that are related to LSPs interfering with DTPT and problems that occur after you install ActiveSync 4.2, ActiveSync 4.5, or WMDC, are as follows:
- After you upgrade from ActiveSync 4.1, DTPT connections may fail.
- When you connect to the desktop, Exchange Server synchronization fails, and you receive the following error code:
When a network request is made from a device through DTPT, two networking connections are made: An incoming connection goes from the device to the desktop over the RNDIS interface, and an outgoing connection goes from ActiveSync to the Internet or to the intranet. The request passes through the Windows networking stack for each connection. Certain proxies and other third-party networking applications may insert themselves into this stack as LSPs. LSPs can prevent Windows Mobile-based devices from making network requests when the Windows Mobile-based devices are connected through DTPT. To try to balance security and corporate policy compliance, ActiveSync and WMDC bypass LSPs on the incoming connection and use LSPs on the outgoing connection. In some cases, the user or the IT administrator may want to change these default settings. An IT administrator may want to use LSPs on the incoming connection for increased security. Or, the user may be experiencing problems because of incompatibilities with the LSP on the outgoing connection. Therefore, the user may want to bypass the LSP.
Starting with ActiveSync 4.1, you must configure the following registry entry to allow for ActiveSync to function together with LSP appliciatons:
[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows CE Services] "AllowLSP"=dword:0
By default, this registry key does not exist. This scenario uses the default value of 00000001. The following tables describe what values to use to configure ActiveSync 4.0, ActiveSync 4.1, and ActiveSync 4.2:
ActiveSync 4.0
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| Value | Incoming connection | Outgoing connection |
|---|
| Not Available | Use LSPs | Use LSPs |
ActiveSync 4.1
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| Value | Incoming connection | Outgoing connection |
|---|
| 00000000 | Bypass LSPs | Bypass LSPs |
| 00000001 | Use LSPs | Use LSPs |
ActiveSync 4.2
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| Value | Incoming connection | Outgoing connection |
|---|
| 00000001 | Bypass LSPs | Use LSPs |
| 00000000 | Bypass LSPs | Bypass LSPs |
| 00000010 | Use LSPs | Bypass LSPs |
| 00000011 | Use LSPs | Use LSPs |
WMDC
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| Value | Incoming connection | Outgoing connection |
|---|
| 00000001 (default) | Bypass LSPs | Use LSPs |
| 00000000 (more compatible) | Bypass LSPs | Bypass LSPs |
| 00000010 | Use LSPs | Bypass LSPs |
| 00000011 (more compliant) | Use LSPs | Use LSPs |
ActiveSync 4.5
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| Value | Incoming connection | Outgoing connection |
|---|
| 00000001 (default) | Bypass LSPs | Use LSPs |
| 00000000 (more compatible) | Bypass LSPs | Bypass LSPs |
| 00000010 | Use LSPs | Bypass LSPs |
| 00000011 (more compliant) | Use LSPs | Use LSPs |