Schedulability analysis of flows scheduled with FIFO: application to the expedited forwarding class

In this paper, we are interested in real-time flows requiring quantitative and deterministic QoS (quality of service) guarantees. We focus more particularly on two QoS parameters: the worst case end-to-end response time and jitter. We consider a FIFO (first in first out) scheduling of flows. The FIFO scheduling is the simplest one to implement and very used. We first establish a bound on the worst case end-to-end response time of any flow in the network, using the trajectory approach. We present an example illustrating our results. Finally, we show how to apply these results to the EF (expedited forwarding) class in a DiffServ (differentiated services) architecture