winxp l2tp without ipsec

winxp默认会使用ipsec来加密l2tp，可以通过修改注册表来取消。win7好像没这个问题。

HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\Rasman\Parameters

Add the following registry value to this key:

Value Name: ProhibitIpSec
Data Type: REG_DWORD
Value: 1

https://support.microsoft.com/en-us/help/258261/disabling-ipsec-policy-used-with-l2tp