In recent years, however, the communication technology
basis for field-level networks has changed, and networks originally
developed for the office information technology (IT)
world (such as Ethernet and wireless solutions) are penetrating
the lowest automation level. The boundaries between the
networks are becoming blurred, and today, it is much more
appropriate to define a field-level network from an application
viewpoint just as a network used in automation, irrespective of
data rates, protocols, or real-time requirements. Nevertheless,
an essential difference between IT and automation is that installations
in the latter domain have much longer lifetimes (ten
years and more compared with typically three for IT systems).
Therefore, as field-level communication technologies progress,
backward compatibility with existing solutions plays an important
role. While this is obvious from an end user’s viewpoint,
it is not easy to achieve in practice and sets limitations to the
range of possible communication architectures.