Integrating Offset in Worst Case Delay Analysis of Switched Ethernet Network With Deficit Round Robbin

Abstract

In order to handle mixed criticality flows in a realtime embedded network, switched Ethernet with Quality of Service (QoS) facilities has become a popular solution. Deficit Round Robin (DRR) is such a QoS facility. Worst-Case Traversal Time (WCTT) analysis is mandatory for such systems, in order to ensure that end-to-end delay constraints are met. Network Calculus is a classical approach to achieve this WCTT analysis. A solution has been proposed for switched Ethernet with DRR. It computes pessimistic upper bounds on end-to-end latencies. This pessimism is partly due to the fact that the scheduling of flows by end systems is not considered in the analysis. This scheduling can be modeled by offsets between flows. This modeling has been integrated in WCTT analysis of switched Ethernet with First In First Out (FIFO) scheduling. It leads to a significant reduction of delay upper bounds. The contribution of this paper is to integrate the offsets in the WCTT analysis for switched Ethernet with DRR and to evaluate the reduction on delay upper bounds, considering a realistic case study.