Energy-Efficient Ethernet

Abstract: In September 2010, the Energy Efficient Ethernet (IEEE 802.3az) standard was officially approved. This new standard introduces a low power mode for the most common Ethernet physical layer standards and is expected to provide large energy savings. In this letter, for the first time, Network Interface Cards (NICs) that implement Energy Efficient Ethernet (EEE) are used to measure energy savings with real traffic. The data presented will be useful to better estimate the energy savings that can be achieved when EEE is deployed. Existing analysis of EEE based on simulations predict a large overhead due to mode transitions between active and low power modes. The experimental results confirm that transition overheads can be significant, leading to almost full energy consumption even at low utilization levels. Therefore traffic patterns will play a key role in the energy savings achieved by EEE as it becomes deployed in the field.

Abstract: The proposed Energy-Efficient Ethernet (EEE) standard reduces energy consumption by defining two operation modes for transmitters and receivers: active and low power. Burst transmission can provide additional energy savings when EEE is used. Collecting data frames into large-sized data bursts for back-to-back transmission maximizes the time an EEE device spends in low power, thus making its consumption nearly proportional to its traffic load. An initial evaluation shows that the additional savings in the scenarios considered range from 5 to 70 percent for conventional users and approximately 50 percent for large data centers.

Abstract: The IEEE 802.3az standard provides a mechanism to build energy efficient Ethernet interfaces via a low power idle mode that they can enter when there is no data to transmit. Several competing algorithms have appeared that make use of this mode to minimize energy consumption with little disruption to the traffic. Two algorithms stand out among those because of their simplicity and performance: frame transmission and burst transmission. Although these algorithms have been shown to be very efficient in simulated scenarios, there is a lack of general analytical models for their behavior. In fact, to this date, the only analyzed traffic patterns have been variants of Poisson traffic. In this paper we provide a general GI/G/1 model for energy consumption and traffic delay for both algorithms. We then develop specializations of the general model for Poisson and deterministic traffic. Finally, we validate the model with the help of both synthetic traffic and real Internet traffic traces.

Abstract: Small or home office (SOHO) Ethernet LAN switches consume about 8 TWh per year in the U.S. alone. Despite normally low traffic load and numerous periods of idleness, these switches typically stay fully powered-on at all times. With the standardization of Energy Efficient Ethernet (EEE), Ethernet interfaces can be put into a Low Power Idle (LPI) mode during idle periods when there are no packets to transmit. This paper proposes and evaluates a new EEE policy of synchronous coalescing of packets in network hosts and edge routers. This policy provides extended idle periods for all ports of a LAN switch and thus enables energy savings deeper than in the Ethernet PHY only. We evaluate our method using an ns-2 simulation model of a LAN switch. We show that our method can reduce the overall energy use of a LAN switch by about 40%, while introducing limited and controlled effects on typical Internet traffic and TCP.