Starting from Windows Server 2008 and Vista SP2 (Service Pack 2), the incomplete simultaneous or concurrent half-open outgoing TCP connections limit is disabled by default. The new behavior allows as many as unlimited half-open TCP connections to be created or established at any time. Users or administrators who want to enforce and enable the concurrent half-open outbound TCP connection attempts limit in Windows Server 2008 SP2, Windows Vista SP2, Windows Server 2008 R2 and Windows 7 must manually configure and set EnableConnectionRateLimiting registry key to impose the half-open TCP connections limit.
Previously in Windows Server 2008 and in Windows Vista with Service Pack 1 (SP1), the system allows for a maximum of ten half-open TCP connections at any time. When the limit is enabled and turned on in Windows Vista SP2, Windows Server 2008 SP2, Windows Server 2008 R2 or Windows 7 based on guide by KB969710 the limit will be ten connections too.
How to Enable Half-Open TCP Connections Limit in Windows Vista with SP2 or Windows 7
- Click Start button.
- Type regedit in the Start Search box, and then click regedit.exe in the Programs list.
- If you are prompted for an administrator password or for confirmation, type your password, or click Continue.
- Locate and then double-click the following registry key:
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\
Tcpip\Parameters\EnableConnectionRateLimiting
Note: In Windows 7, user has to create a new DWORD (32-bit) Value registry entry under Parameters subkey, and named the new value data as EnableConnectionRateLimiting.
- In the Value data box, type 1, and then click OK.
- Exit Registry Editor.
- Restart the computer (in fact, the change takes effect immediately without the need to reboot).
The registry key works on all 32-bit (x86) and 64-bit (x64) edition of Windows Vista with SP2 and Windows Server 2008 with SP2, and unofficially, Windows 7.
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