Adaptive Batch Scheduling for Packet Switching with Delays

We discuss the control of a packet switch where delays due to mode switching become important. Whereas most packet switch scheduling analysis assumes that switches can operate with negligible delays, we consider what to do when this does not hold. Several practical situations can indeed lead to a time-lag in switches, where changing physical connections in the switch can take a significant time relative to the high data rates processed in the fabric. If switches are forced to change modes too frequently, this leads to a loss of throughput. This chapter provides a synthesis of recent developments in packet switch scheduling with delays. We present an overview of how to manage a switch when there are forced delays at the switch; that is, when the required time to change from one switching mode to another is non-trivial. If traditional policies such as weighting-based or online fixed batch sizes are utilized, there can be a loss of throughput. We will discuss the result that adaptive batch scheduling algorithms maintain maximal throughput in a switch even in the presence of nontrivial delays.