Schedulability criterion and performance analysis of coordinated schedulers

Inter-server coordinated scheduling is a mechanism for downstream nodes to increase or decrease a packet´s priority according to the congestion incurred at upstream nodes. In this paper, we derive an end-to-end schedulability condition for a broad class of coordinated schedulers that includes Core-stateless Jitter Virtual Clock (CJVC) and Coordinated Earliest Deadline First (CEDF). In contrast to previous approaches, our technique purposely allows flows to violate their local priority indexes while still providing an end-to-end delay bound. We show that under a simple priority assignment scheme, coordinated schedulers can outperform WFQ schedulers, while replacing per-flow scheduling operations with a simple coordination rule. Finally, we illustrate the performance advantages of coordination through numerical examples and simulation experiments.