Real-time communication for industrial embedded systems using switched Ethernet

This paper focuses on developing and analyzing support for real-time traffic over a switched Ethernet network without any hardware or protocol modifi- cations. Network architecture with full-duplex switched Ethernet and endnodes has been assumed. The switch and the end nodes control the real-time traffic with Earliest Deadline First (EDF) scheduling on the frame level. No modification to the Ethernet standard is needed in the network that supports both real-time and non-real -time TCP/IP communication. The switch is responsible for admission control where feasibility analysis is made for each link between source and destination. All added traffic handling to support real-time communication is positioned in a thin layer (RT layer) added between the Ethernet layer and the TCP/IP suite. This assures adaptation to the surrounding protocol standards. The RT layer manages traffic on the basis of virtual connections, denoted as RT channels, as well as packet level scheduling. RT channels are created between end-nodes prior to any occurrence of real-time traffic. The comparison of two deadline-partitioning schemes, to partition the delay budget over the links for a path, is also presented. While SDPS (Symmetric Deadline Partitioning Scheme) is straightforward to implement, ADPS (Asymmetric Deadline Partitioning Scheme) is devised in order to have a more flexiblefeasibilitytest. ADPSshows promises in removing bottlenecks from links, especially when a master-slave communication is considered as the traffic pattern, and ADPS proves to be a better choice than SDPS