On the Impact of Packet Scheduling on End-to-End Delays in Large Networks

We seek to provide an analytical answer whether the impact of packet scheduling algorithms on end-to-end delays diminishes on long network paths. The answer is provided through a detailed multi-node delay analysis, which is applicable to a broad class of scheduling algorithms, and which can account for statistical multiplexing. The analysis is enabled by two contributions: (1) We derive a function that can characterize the available bandwidth at a node for various scheduling algorithms. This characterization is sharp enough to provide necessary and sufficient conditions for satisfying worst-case delay bounds at a single node; (2) We obtain end-to-end delay bounds by solving an optimization problem, in which the service received at multiple nodes is subsumed into a single function. Since our unified analysis captures the properties a broad group of schedulers in a single parameter, it can provide insight how the choice of scheduling algorithms impacts end-to-end delay bounds. An important finding of this paper is that some schedulers show noticeable performance differences which persist in a network setting with long paths. Index Terms Delay Analysis, Scheduling, End-to-End Delays, Network Calculus.