Leveraging Energy Saving Capabilities of Current EEE Interfaces via Pre-Coalescing

TL;DR

This paper enhances energy models for Energy Efficient Ethernet by including hysteresis delays and proposes source-based frame coalescing to improve energy savings without sacrificing performance.

Contribution

It introduces an augmented energy model accounting for hysteresis delays and proposes source-based frame coalescing with optimal parameters for better energy efficiency.

Findings

Most existing EEE devices cannot achieve significant energy savings due to hysteresis.

Source-based frame coalescing can improve energy efficiency of EEE interfaces.

Optimal coalescing parameters depend on device configuration and traffic conditions.

Abstract

The low power idle mode implemented by Energy Efficient Ethernet (EEE) allows network interfaces to save up to 90% of their nominal energy consumption when idling. There is an ample body of research that recommends the use of frame coalescing algorithms---that enter the low power mode as soon as there is no more traffic waiting to be sent, and delay the exit from this mode until there is an acceptable amount of traffic queued---to minimize energy usage while maintaining an acceptable performance. However, EEE capable hardware from several manufactures delays the entrance to the low power mode for a considerable amount of time (hysteresis). In this paper we augment existing EEE energy models to account for the hysteresis delay and show that, using the configuration ranges provided by manufacturers, most existing EEE networking devices are unable to obtain significant energy savings. To improve their energy efficiency, we propose to implement frame coalescing directly at traffic sources, before reaching the network interface. We also derive the optimum coalescing parameters to obtain a given target energy consumption at the EEE device when its configuration parameters are known in advance.