System Foundations for a Multiuser Environment

Windows NT provides a strong foundation for a multiuser system largely because the network operating system is integrated with the native operating system. With WinFrame, Citrix Systems took advantage of this foundation and created a system of multiuser primitives (low-level APIs), extending and exploiting these foundations. Citrix further enabled these foundations by adding the Independent Computing Architecture (ICA) system services, protocol, and client to the mix. Bob Williams, Director of ICA Architecture at Citrix Systems and Chairman of the Open ICA Forum, lists these features intrinsic to Windows NT that enabled Citrix to build concurrent multiuser access:

Windows NT provides a strong foundation for the development of a multiuser system.

• User profiles A collection of configuration data that ap-plies only to a specific user. Each time the user logs on, the system retrieves this information and configures the environment to that user’s settings.
  
  
• Embedded logon Users must log on to access a Windows NT–based computer. The logon generates an access token containing the user’s security and group identifiers. Every action that takes place on Windows NT has an attached access token to create barriers between different users’ contexts.
  
  
• Symmetric multiprocessing support (SMP) SMP is a feature of Windows NT that lends itself to the power re-quired for multiuser access. SMP allows multiple processors on one machine to work together for increased system performance. Each processor has full access to hardware, bus, and memory actions.