Windows Server 2008 builds on the success and strengths of its Windows Server predecessors while delivering valuable new functionality and powerful improvements to the base operating system. New Web tools, virtualization technologies, security enhancements, and management utilities help save time, reduce costs, and provide a solid foundation for your information technology (IT) infrastructure. A Device CAL permits one device (used by any user) to access or use the server software. Device CALs are likely to be more cost-effective than User CALs if there are multiple users per device (for example, a call center or an airport kiosk). Software Assurance (SA) is Microsoft's maintenance program that provides product support, software upgrades, and more.