Abstract—Field-level networks have been one of the keys to
modern automation systems. Be it in factory, process, or building
automation, networks allow for horizontal and vertical integration
of distributed devices and functions. This paper reviews the evolution
of field-level networks comprising fieldbus systems, industrial
Ethernet, and recent industrial wireless networks. The main focus
is on demonstrating the continuity in the development of the three
generations that ensured backward compatibility at the expense of
radical innovation. Given the wide set of modern communication
technologies, this paper then discusses how architectures for future
automation networks might look. Particular emphasis is put
on hybrid architectures for combined wired/wireless networks. A
generic concept for integration of multiple wireless segments will
be presented that supports seamless roaming for mobile nodes in
industrial environment.