Microsoft Knowledge Base Article 912222 contains the following introduction:

This article describes the Microsoft Windows Server 2003 Scalable Networking Pack release. This is an out-of-band (OOB) release. The Windows Server 2003 Scalable Networking Pack is released for the following stock-keeping units (SKU):

   Microsoft Windows Server 2003 Service Pack 1 x86

   Microsoft Windows Server 2003 Service Pack 1 x64

   Microsoft Windows XP x64

The Windows Server 2003 Scalable Networking Pack contains stateful and stateless offloads to accelerate the Windows network stack. The update includes the following features:

   TCP Chimney offload

   Receive Side Scaling (RSS)

   Network Direct Memory Access (NetDMA)