Windows Server 2003 Scalable Networking Pack & slow data transfers

Overview -- Windows Server 2003 Scalable Networking Pack

The architectural goal of the Scalable Networking initiative is to scale applications in the Windows family of operating systems to new levels of performance at a variety of cost points. Because of the variety of cost points and because of the variation in workload, the initiative includes the following two fundamental approaches:

    * Stateful offloads
    * Stateless offloads

TCP Chimney is a stateful offload. TCP Chimney offload enables TCP/IP processing to be offloaded to network adapters that can handle the TCP/IP processing in hardware. Each TCP Chimney offload-capable network adapter has a finite number of connections that it can support in hardware. TCP connections will be offloaded to hardware as long as the hardware can support these connections. After the hardware offload connection limit has been reached, all additional connections are handled by the host stack.

The Microsoft Windows Server 2003 Scalable Networking Pack release
http://support.microsoft.com/kb/912222

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However, after you install Windows Server 2003 Service Pack 2 (SP2) or Windows Server 2003 Scalable Networking Pack (SNP) on a computer that has a TCP/IP Offload-enabled network adapter, you may experience many network-related problems.

The SNP feature was to offload the processing of network packets from the CPU to the Network card.  This has caused more issues than helping the network enhancements. And this is a major issue if the network card is a Broadcom network card -- which is the most widely installed NIC on all servers.

An update to turn off default SNP features is available for Windows Server 2003-based and Small Business Server 2003-based computers
http://support.microsoft.com/kb/948496