Windows 2003 SP2 and NAT compatibility issues

New feature features are added to Windows Server 2003 SP2: Extensible Network Toolkit (Scalable Networking PACK,SNP). The following three features are included in this Extensible Network Toolkit:

LTCP load transfer (TCP Chimney Offload): Transfers the processing of TCP packets from the CPU to the network adapter hardware, thereby greatly reducing CPU performance while processing TCP packets;

L Receive-side regulation (receive-side scaling): When receiving data, the CPU processing capacity is dynamically distributed to all CPUs of the system, and the performance of data receiving is dynamically adjusted according to system load and network processing performance, so that the network throughput obtains the highest performance.

LNETDMA: Through the direct memory access of hardware devices, NETDMA can achieve more efficient memory management, thereby improving network throughput performance.

Although SNP greatly improves the network processing performance of Windows Server 2003, because of its working principle, there may be a compatibility problem between SNP and Nat. On a server with Windows Server 2003 SP2 on the operating system, there may be situations where NAT cannot be used properly. This is because the receiver-side throttling function transfers the processing of the TCP hash value from the CPU to the network adapter hardware, but because NAT modifies the header information in the IP packet, causing the TCP hash value computed by the network adapter hardware to be inconsistent with the TCP hash computed by NAT, This causes the TCP connection to be reset, which eventually causes the NAT to work abnormally.

In order to solve this problem, it can be solved temporarily by prohibiting the receiving-end adjustment function, and the specific operation process is:

In

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters

Next, add a name that is:

Enablerss

DWORD key value and sets its value to 0.

Microsoft has launched the relevant patches:

KB948496 an update to turn off default SNP features was available for Windows Server 2003-based and Small Business server 2 003-based Computers

Download Address:

Http://support.microsoft.com/kb/948496/en-us