Delay Bounds in a Network with Aggregate Scheduling

Abstract

A large number of products implementing aggregate buffering and scheduling mechanisms have been developed and deployed, and still more are under development. With the rapid increase in the demand for reliable end-to-end QoS solutions, it becomes increasingly important to understand the implications of aggregate scheduling on the resulting QoS capabilities. This paper studies the bounds on the worst case delay in a network implementing aggregate scheduling. We derive an upper bound on the queuing delay as a function of priority traffic utilization and the maximum hop count of any flow, and the shaping parameters at the network ingress. Our bound explodes at a certain utilization level which is a function of the hop count. We show that for a general network configuration and larger utilization utilization an upper bound on delay, if it exists, must be a function of the number of nodes and/or the number of flows in the network.