Delay Analysis of Timer-Based Frame Coalescing in Energy Efficient Ethernet

IEEE 802.3az, also known as Energy Efficient Ethernet (EEE), aims at reducing the energy consumption of an Ethernet link by placing it in sleep mode when the link is idle. Frame coalescing mechanism proposed for EEE is an effective means to increase the average idle time of the link, thus reducing the overhead stemming from sleep/wake transitions, but at the expense of increased frame delays. Therefore, it is imperative to quantify the energy-delay trade-off while employing frame coalescing. As opposed to existing delay models that focus only on the average delays, a simple but exact queuing model is introduced for timer-based frame coalescing to find the delay distribution when the frame arrival process is Poisson and frame lengths are generally distributed. An expression for average saving in power consumption is also provided.