Dual-mode Energy Efficient Ethernet with Packet Coalescing: Analysis and simulation

Abstract

The recently-proposed and studied Dual-Mode Energy Efficient Ethernet (EEE) amends the conventional EEE with an additional low-power mode called Fast Wake. Dual-Mode EEE has shown to be much more effective than EEE in reducing the power consumption of Ethernet links at 40Gb/s and higher due to impractically-high transition times of using only one low-power mode at these capacities. However, even with two low-power modes, the still relatively-high transition times between the modes prevent Dual-Mode EEE from taking full advantage of the power reduction of the low-power modes and approach energy-proportional operation.We design and formulate Packet Coalescing for Dual-Mode EEE links at 40Gb/s and higher. Packet Coalescing is to collect multiple packets before transmitting them on a link as a burst of back-to-back packets. By coalescing packets into bursts, the overhead of transition times can be reduced and nearly energy-proportional operation can be achieved, albeit at the expense of a bounded increase in the packet delay. We analytically model the power consumption of Dual-Mode EEE with Packet Coalescing and present closed-form formulae for the average percentage of time a link would spend in each low-power mode and transition. We also simulate a 40Gb/s Dual-Mode EEE link with Packet Coalescing and present results suggesting that the compromise in the average per-packet delay is likely to be worthwhile under most circumstances considering the power reduction.