iRED: A Disaggregated P4-AQM Fully Implemented in Programmable Data Plane Hardware

Routers use queues to temporarily hold packets when they can’t process them immediately. Congestion occurs when the arrival rate of packets exceeds the processing capacity, leading to increased queuing delay. Active Queue Management (AQM) strategies aim to reduce congestion and queuing delay by draining packets from queues. Traditionally, AQMs are placed in the Egress pipeline of Programmable Data Plane (PDP) hardware due to the availability of queue delay information there. We argue that this approach wastes the router’s resources because the dropped packet has already consumed the entire pipeline of the device. We propose ingress Random Early Detection (iRED) as a more efficient P4-AQM approach fully implemented in PDP hardware, that introduces the concept of disaggregated AQM, effectively resolving the egress drop problem. iRED also supports the Low Latency, Low Loss, and Scalable Throughput (L4S) framework, saving device pipeline resources by dropping packets in the Ingress block. Our experiments with a Tofino2 programmable switch achieved a rate of 1Tbps and show that iRED can reduce router resource consumption by up to 10x in memory usage, 12x fewer processing cycles, and 8x less power consumption for the same traffic load. It achieves fairness in bandwidth usage for different types of traffic and significantly improves Quality of Service (QoS) in Dynamic Adaptive Streaming over HTTP (DASH) with up to a 2.34x improvement in Frames Per Second (FPS) and a 4.77x increase in video player buffer fill. We believe this is a pioneering work to highlight the egress drop problem and deeply explore its potential damage to network performance.