QFloor: Queue Delay Reduction in Dynamic Backpressure Networks

Abstract

QFloor addresses the high queuing delays inherent in backpressure forwarding, including in dynamic or oscillatory networks. QFloor is purely local and reactionary: it adds placeholder bytes to the advertised queue values with the explicit goal of keeping the minimum queue depth at a static pre-configured number of bytes. QFloor deals with queue depth dynamics by looking at the queue depth over a dynamically-sized observation window of time, adding placeholder bytes if that minimum depth is too high, and removing placeholder bytes whenever the backpressure algorithm dictates a dequeue from a queue with only placeholder bytes. Experimentation in a fully-implemented backpressure forwarding system shows that QFloor can reduce the end-to-end latency by more than 90% even in a network with only one and two-hop paths.