Guaranteed Real-Time Services in Switched Ethernet Networks with Deadline Scheduling in the End Nodes

This paper proposes a switched Ethernet network that supports real-time communication with guaranteed bit rate and end-to-end delay bound. In our proposal, the source nodes use Earliest Deadline First (EDF) scheduling, while the switch uses First Come First Served (FCFS) to control periodic real-time traffic belonging to logical realtime connections. The schedulability condition is drawn and the end-to-end worst-case delay bound is derived for guaranteed real-time traffic, which also gives, as a sub-result, the needed buffer space in the switch. Moreover, different traffic classes are prioritized and put into different output queues in the end nodes and the switch, which minimizes the interference with other traffic when transmitting periodic time-critical messages. The solution requires no additional hardware or software modifications of the switch and the underlying standard. It is based purely on software implementation in the end nodes. Furthermore, the EDF scheduling strategy used in the source nodes allows good resource utilization, while the FCFS scheduling used in the switch limits the switch processing overhead. The paper presents simulation analysis for Fast Ethernet, which verifies our approach of guaranteeing real-time transmission at the same time as achieving high utilization.