This chapter focuses on several topics related to the industrial Internet of the things (IIoT). Starting with current loop signalling in industrial plants and fmishing with wireless networks, the main strengths, weaknesses, opportunities and threats of IIoT are underlined. The first part of the chapter includes a summary of the main protocols that are still used in instrumentation and control (I&C) networks and the second part of the chapter presents topics related to industrial Ethernet, real-time demands, collision avoidance, synchronization and time -sensitive requirements in industrial networks.