Fieldbuses are defined as a family of communication media specified for industrial applications. They usually interconnect embedded systems. Embedded systems exist everywhere in the modern world, they are included in simple personal technology as well as the most advanced spaceships. They aid in producing a specific task, often with the purpose to generate a greater system functionality. These kinds of implementations put high demands on the communication media. For a medium to be applicable for use in embedded systems, it has to reach certain requirements. Systems in industry practice react on real-time events or depend on consistent timing. All kinds are time sensitive in their way. Failing to complete a task could lead to irritation in slow monitoring tasks, or catastrophic events in failing nuclear reactors. Fieldbuses are optimized for this usage. This thesis aims to research fieldbus theory and connect it to industry practice. Through interviews, requirements put on industry are explored and utilization of specific types of fieldbuses assessed. Based on the interviews, guidelines are put forward into what fieldbus techniques are relevant to study in preparation for future work in the field. A discussion is held, analysing trends in, and synergy between, state of the art and the state of practice. A strong momentum is identified. The traditional communication media Ethernet, not originally intended for time-sensitive industry appliances, are expanding throughout the field, both in research and, maybe most interestingly, in practice. It is mainly motivated through qualities of somewhat lesser technical significance. A plethora of methods have emerged trying to optimize Ethernet for real-time purposes, each one resulting in some drawbacks, which are in turn addressed. In the end of this paper, the large-scale trend of Real-Time Ethernet is questioned and discussed.