Fair and Delay Adaptive Scheduler (FDAS) preliminary modeling and optimization

Fair and Delay Adaptive Scheduler (FDAS) is a scheduling mechanism that dynamically adapts to the incoming traffic flows' requirements in term of bandwidth allocation, delay bounds and packet loss restrictions. It performs this utilizing both virtual finish time fluid scheduling along with schedulability and delay sensitive scheduling. The former ensures that the flows receive a fair share of the available output throughput while the later ensures that time critical flows that are about to expire will receive preferential treatment when needed to avoid getting garbled and dropped when possible. FDAS tries to maximize the satisfaction as perceived by incoming traffic flows through balancing between bandwidth fairness and delay bound accommodation. FDAS acts as a hybrid scheduler that tries to overcome fairness allocation problems due to preferential treatment for the soon-to-expire packets which happens in Earliest Deadline First (EDF) schedulers. Meanwhile, it tries to minimize the number of packets that violate their deadlines for transmission and get garbled accordingly that happens on Weighted Fair Queuing (WFQ) and its derivatives. In this paper, we try to answer the question of how many of the flows and how much of their traffic can be accommodated in terms of delay bound and throughput requirements given the incoming mixture of traffic with diverse QoS requirements. FDAS preliminary modeling and optimization is discussed in this paper to answer the above question in a manner that maximizes the overall performance satisfaction as perceived by incoming flows taking into consideration traffic priorities, if any.