The MS-DOS-based client Network Access Program (NAP) provides full support for applications that allow switching between foreground and background operation (that is, terminate-and-stay-resident (TSR) applications), including fully preemptive scheduling of a background thread.
To avoid possible interaction problems, it is important that client applications that intend to support background operation make use of the facilities provided by the NAP, rather than implementing separate scheduling mechanisms hooked from MS-DOS interrupts.