Packet Coalescing for Dual-Mode Energy Efficient Ethernet: A Simulation Study

Energy Efficient Ethernet (EEE) is a standard that introduces a Low Power Idle (LPI) mode to Ethernet links to reduce their power consumption between packet transmissions. An EEE link can transition to LPI when there are no packets in its buffer to transmit - idle periods. Transition times to and from LPI are significantly high, which prevents EEE from taking full advantage of the link's idle periods. Packet coalescing is to collect multiple packets before sending 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.

Only one LPI mode as described above is defined for Ethernet links with the capacity of 10 Gb/s and lower. However, two modes of low-power operation are defined for EEE links at 40 Gb/s and higher; Fast Wake and Deep Sleep. The Dual-Mode EEE can achieve significant savings that may not be achievable with a single LPI mode. In this paper, applying packet coalescing to Dual-Mode EEE is studied. Performance evaluation using simulation shows that packet coalescing can result is nearly energy-proportional operation in Dual-Mode EEE for 40 Gb/s and above, albeit with some modifications and trade-offs.