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energy efficient ethernet

How Efficient Is Energy-efficient Ethernet?

In recent years there has been an increase in awareness of energy efficiency in many areas including the network community. In response to such requirements, the IEEE recently released the 802.3 az standard that provides a way for physical Ethernet interfaces to enter low power mode when there is no shipping traffic. 

At the same time proposals are beginning to emerge on how to control the physical interface state between active power modes and low power consumption except that the standard leaves undefined so that different suppliers can compete. 

In this paper, we provide accurate analytical models for two of these sleep algorithms frame transmission and burst transmission methods which stand out for their simplicity and good performance in several simulation studies. 

The proposed models will assist in a fair comparison of these algorithms and the analysis of the impact of the configuration parameters and physical characteristics of the line card in their expected savings.

Energy-Efficient Ethernet

The first wave of network equipment with energy efficiency in mind is about to arrive. And other energy-saving ideas in grids are on the doorstep.

When most people think of the Energy Star program the products that probably come to mind include lighting home appliances and electronics. But because government policymakers are accelerating and expanding energy-saving efforts some industries are paying more attention arguing that it is better to launch their own initiatives before the mandate is done.

This is the case with the Energy Efficient 802.3 az Ethernet (EEE) standard of the Institute of Electrical and Electronics Engineers (IEEE). As its name implies it strives to reduce energy in wired Ethernet connections. It was adopted by the IEEE last September. (See "The Way to Fix EEE", next page.)

Ethernet of course is the dominant technology of wires for communication in computer networks. It is also considered for use in access networks and even for long-term links.

In short, the IEEE program saves energy by blasting data over Ethernet lines then anesthetizing the network controllers until they are required again. 

More specifically the .az part is tuned to the four different standard rates used for twisted pair (UTP) unprotected wiring which make up the vast majority of Ethernet links nowadays: 10Mbps (1-BASE-T), 100Mb its / sec (100BASE-TX), 1 Gbit / sec (1000BASE-T and 10 Gbits / sec (10GBASE-T).

It is estimated that the IEEE 802.3 az standard could save $ 400 million a year in the U.S. alone. PHY) typically consumes about 0.5 watts of power while a 10GBASE-T device consumes about 5 watts.

Michael Bennett of the Lawrence Berkeley National Laboratory (LBNL) and IEEE P802.3az task force chairman say the new standard could explain energy savings ranging from 1.73 to 2.60 TWh per year in residential equipment in the US only. This is reflected in energy cost savings of $ 139 to $ 208 million per year. 

For commercial equipment for data centers such as servers storage systems switches routers etc., energy savings can range from 1.47 to 2.21 TWh per year in the United States alone. This translates into savings of $ 118 to $ 177 million per year.

The official term for the energy-saving technique given by the IEEE P 802.3 az task force is low power consumption (LPI). There is general agreement that it can be challenging to quickly activate a dormant network card as stated by LPI. 

But it is much easier than an alternative method evaluated by the task force called Adaptive Link Rate (ALR). 

ALR uses a two-way access control frame (MAC) handshake. It can be implemented in the driver or inside the Ethernet controller.

The problem: this concept is time-consuming when switching between Ethernet speeds (i.e. higher data rates to lower and vice versa). Changing the link rate means lowering the link rate and then re-establishing it which can take a few microseconds too slow for modern networks.

The idea of ​​LPI was conceived at Intel. "You should send data faster and fall asleep faster allowing you to save more power over time," says Robert Hayes Intel's strategic network planner. Most energy-efficient Ethernet data traffic comes in bursts and is therefore suitable for LPI access, he explains.

Link utilization packet delivery time and packet spacing determine the energy efficiency of the EEE concept. 

Mission force members believe that EEE overhead is likely to consume the same amount of force as packet transfer. Many studies have found that utilization of network links especially at the edge is generally low driven by the need for data transfer or rapid demand for bulk.

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