Identifying Sources of Pessimism in the Trajectory Approach with FIFO Scheduling

Switched Ethernet has been used in critical industrial networks such as in avionic and nuclear sectors. For qualification purposes, before deploying the network, we are interested in computing deterministic upper bounds on the end-to-end response time of flows existing in the network. This paper focuses on one of the approaches that can be used to determine an upper bound on the end-to-end response time of a flow. It is called the Trajectory Approach. We describe briefly the concept on which this approach is based. Moreover, we identify the source of pessimism introduced by this approach in the case of FIFO scheduling. Finally, we show on a small network configuration how the sources of pessimism may affect the tightness of the upper bound of the end-to-end response time computed using the Trajectory Approach.