This chapter gives an overview on various real-time communication protocols, from the Controller Area Network (CAN) that was standardized over twenty years ago but is still popular, to the FlexRay protocol that provides strong predictability and fault tolerance, to the more recent Ethernet-based networks. The design of these protocols including their messaging mechanisms was driven by diversified requirements on bandwidth, real-time predictability, reliability, cost, etc. The chapter provides three examples of real-time communication protocols: CAN as an example of event-triggered communication, FlexRay as a heterogeneous protocol supporting both time-triggered and event-triggered communications, and different incarnations of Ethernet that provide desired temporal guarantees.