RT-EP: A Fixed-Priority Real Time Communication Protocol over Standard Ethernet

This paper presents the design and implementation of RT-EP (Real-Time Ethernet Protocol), which is a software-based token-passing Ethernet protocol for multipoint communications in real-time applications, that does not require any modification to existing Ethernet hardware. The protocol allows a fixed priority to be assigned to each message, and consequently well-known schedulability analysis techniques can be applied. A precise model of its timing behavior has been obtained. Furthermore, this protocol provides the ability of recovering from some fault conditions. It has been ported to an implementation of the Minimal Real-Time POSIX standard called MaRTE OS [10], and is being used to support real-time communications in an implementation of Ada’s Distributed Systems Annex (RT-GLADE). It has been successfully used to implement a distributed controlled for an industrial robot.