Mapping application layer functionalities to DLL mechanisms in a process control environment

The paper deals with the mapping of application layer (AL) services to the data link layer (DLL) procedures in real-time distributed process control communication systems. These systems have, generally, a reduced number of levels which supports all and only the functions which are essential for time-critical applications. This aims to streamline as much as possible the vertical mapping and coding activity (typical of layered architectures and particularly onerous in OSI). The aim of the paper is to analyze some possible mapping of the functions offered by the application relationship (AR) model (which seems to provide the most critical functions) on those available at the DLL, referring at this level both to centralized (IEC/ISA FieldBus and FIP) and distributed access protocols