With the advent of native support for TCP offload in Windows introduced by Microsoft's SNP [Scalable Networking Pack] comes a new driver architecture for Alacritech TCP offload hardware. From this point on, all Alacritech Accelerator drivers can now be classified as either SNP drivers or ATCP drivers.

Windows Server 2003 x86 supports both SNP and ATCP drivers. For Windows Server 2003 x86, unless specific features provided by the ATCP drives are required, SNP aware drivers are prefered.

SNP Drivers

SNP aware drivers are those that are designed to work in conjunction with Microsoft's Scalable Networking Pack. These drivers will only work on systems that support SNP, and only if SNP is installed.

SNP aware drivers will have a major number of 9 or higher (9.x.x.x).

SNP Drivers NDIS version

SNP drivers are sometimes refered to by their NDIS version. NDIS stands for Network Driver Interface Specification. Microsoft operating system versions can be categorised by their NDIS version. If we refer to a driver by it's NDIS version, it's usually just as a shorthand for the operating systems. We might say "NDIS 5.2 driver" rather than "driver for Windows Server 2003 and XP x64" simply because it's more convenient.

The NDIS versions of selected Microsoft operating systems are:

MS Windows NDIS Versions

Windows Version	NDIS Version	Uses SNP Architecture?
Windows 98, 98 SE, Me, 2000	NDIS 5.0	No
Windows XP, Server 2003	NDIS 5.1	No
Windows Server 2003 SP2, XP x64 SP2	NDIS 5.2	Yes
Windows Vista	NDIS 6.0	Yes
Windows Vista SP1, Server 2008	NDIS 6.1	Yes
Windows 7, Server 2008 R2	NDIS 6.2	Yes

ATCP Drivers (Also known as Non-SNP Aware Drivers)

ATCP drivers are those that use Alacritech's original parallel stack architecture as embodied by the atcp.sys driver file. These drivers are either legacy drivers that were released prior to the existance of SNP, or drivers destined for Windows versions that don't support SNP.