WinServer 2003 SP2 compatibility issues with NAT

A new feature in Windows Server 2003 SP2: Scalable Networking Pack (SNP). The following three aspects are included in this Scalable Networking Toolkit:

lTCP Load Transfer (TCP Chimney Offload): The processing of TCP packets is transferred from the CPU to the network adapter hardware, thus greatly Reduce the CPU performance occupied when processing TCP packets;

l Receive-side Scaling: When receiving data, dynamically distribute the required CPU processing power to all CPUs of the system. And dynamically adjust the performance of data reception based on system load and network processing performance, so that network throughput can achieve the highest performance.

lNetDMA: Through the direct memory access function 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, due to its working principle, there may be compatibility issues between SNP and NAT. On a server with Windows Server 2003 SP2 operating system, NAT may not work properly. This is because the receiver adjustment function transfers the processing of TCP hash calculation from the CPU to the network adapter hardware, but because NAT will modify the header information in the IP packet, resulting in the TCP hash value calculated by the network adapter hardware. The TCP hash value calculated by the NAT is inconsistent, which causes the TCP connection to be reset, and eventually the NAT does not work properly.

For this problem, you can temporarily solve the problem by disabling the receiving end adjustment function. The specific operation process is:

Add a name under

HKEY_LOCAL_MACHINESYSTEMCurrentControlSetServicesTcpipParameters

For:

EnableRSS

DWORD key and set its value to 0.

Microsoft will launch related patches in the future.