Abstract-In this paper, we study the power efficiency and delay performance of the IEEE 802.3az Energy Efficient Ethernet (EEE) protocol. A new approach is proposed to analyze the M/G/1 queue with the vacation time that is governed by the arrival process and the parameter τ and N of the BTR strategy. Our key idea is to establish the connection between the vacation time and the arrival process to account for their dependency. We first derive the distribution of the number of arrivals during a vacation time based on an event tree of the BTR strategy, from which we obtain the mean vacation time and the power efficiency. Next, from the condition on the number of arrivals at the end of a vacation period, we derive a generalized P-K formula of the mean delay for EEE systems, and prove that the classical P-K formula of the vacation model is only a special case when the vacation time is independent of the arrival process. Our analysis demonstrates that the τ policy and N policy of the BTR strategy are compensating each other. The τ policy ensures the frame delay is bounded when the traffic load is light, while the N policy ensures the queue length at the end of vacation is bounded when the traffic load is heavy. These results, in turn, provide the rules to select appropriate τ and N . Our analytical results are confirmed by simulations.Index Terms-Ethernet, IEEE802.3az, EEE protocol, M/G/1 queue with vacation, P-K formula.

This paper investigates the dual-mode power-saving strategy designed for the 100G Energy Efficient Ethernet. The process of this strategy is a sequence of cycles, where each cycle is an interval elapsed between two consecutive instants when the buffer of the Ethernet interface becomes empty. In each cycle, the interface first enters the fast-wake mode to perform the conditional sleep-mode selection of the strategy. If the number of arrivals during the fast-wake mode reaches a threshold, the interface directly wakes up; otherwise, it proceeds to the deep-sleep mode. The sequence of cycles switches between two types: deep-sleep cycles with deep-sleep mode and light-sleep cycles without deep-sleep mode. We analyze the dual-mode strategy based on the condition of the number of arrivals during the fast-wake mode. We first derive the weights of conditions according to the feature of the conditional sleep-mode operation, and then calculate the unconditioned performance measure of the dual-mode strategy based on the weighted average of that of these two kinds of cycles. Finally, we obtain the close-form expressions of the power efficiency and the mean delay, based on which we provide a set of parameter selection rules. We show that the dualmode strategy with these rules can select suitable sleep modes according to the instantaneous traffic rate, and thus perform well under bursty input traffic. INDEX TERMS 100G Energy Efficient Ethernet, dual-mode strategy, performance tradeoff, threshold selections.

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