Power Efficiency and Delay Tradeoff of 10GBase-T Energy Efficient Ethernet Protocol

Abstract

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.

Dynamic EEE Coalescing: Techniques and Bounds

“…and then the optimal queue threshold can be estimated as Figure 2 shows the timer durations and the queue thresholds computed using (12) and (16) to maintain different average queuing delays (τ = 16, 32 and 64 µs) with 1500-byte frames. The queue thresholds obtained solving cubic equation (13) are not shown in Fig. 2(b) since they are indistinguishable from those obtained with approximation (16).…”

“…Finally, [13] provides rules to select the appropriate queue threshold and timer duration values to comply with the average delay requirement when using both size-based and time-based coalescing jointly. [14] also obtains similar results for the case of sleeping base stations using size-based coalescing.…”

“…This assures a quick reaction to variable traffic conditions. However, note that the computation of the optimal coalescing parameters requires accurate estimations of the average arrival rate λ and the W 0 delay, as shown in (12) and (13). But the computation of W 0 requires, in turn, to estimate the average service rate (required to compute the utilization ρ) and the variances of both interarrival and service times, as shown in (3).…”

Leveraging energy saving capabilities of current EEE interfaces via pre-coalescing

“…These models have been later employed to tune the frame coalescing algorithm, i.e., deriving the optimum upper bound, so as to obtain a given energy efficiency [7] or to meet a target average delay by limiting the maximum time in LPI [23,25].…”

“…This coalescing approach [4] clearly trades some delay for greater energy savings [5,6]. Many coalescing proposals employ the number of queued frames as the condition to exit LPI, but time-based coalescers, that use the time since the first frame arrival while in LPI, can also be configured to obtain identical results [7,8].…”