computer network A computer network is a set of computers sharing resources located on or provided by network nodes. The computers use common communication protocols over digital interconnections to communicate with each other. These interconnections are ...

ing, Energy-Efficient Ethernet (EEE) is a set of enhancements to

twisted-pair Twisted pair cabling is a type of wiring used for communications in which two conductors of a single circuit are twisted together for the purposes of improving electromagnetic compatibility. Compared to a single conductor or an untwisted ba ...

, twinaxial,

backplane A backplane (or "backplane system") is a group of electrical connectors in parallel with each other, so that each pin of each connector is linked to the same relative pin of all the other connectors, forming a computer bus. It is used as a back ...

, and

optical fiber An optical fiber, or optical fibre in Commonwealth English, is a flexible, transparent fiber made by drawing glass (silica) or plastic to a diameter slightly thicker than that of a human hair. Optical fibers are used most often as a means to ...

Ethernet physical-layer variants that reduce power consumption during periods of low data activity. The intention is to reduce power consumption by 50% or more, while retaining full compatibility with existing equipment. The

Institute of Electrical and Electronics Engineers The Institute of Electrical and Electronics Engineers (IEEE) is a 501(c)(3) professional association for electronic engineering and electrical engineering (and associated disciplines) with its corporate office in New York City and its operation ...

(IEEE), through the IEEE 802.3az task force, developed the standard. The first study group had its call for interest in November 2006, and the official standards task force was authorized in May 2007. The IEEE ratified the final standard in September 2010. Some companies introduced technology to reduce the power required for Ethernet before the standard was ratified, using the name Green Ethernet. Some energy-efficient switch

integrated circuits An integrated circuit or monolithic integrated circuit (also referred to as an IC, a chip, or a microchip) is a set of electronic circuits on one small flat piece (or "chip") of semiconductor material, usually silicon. Large numbers of tiny ...

were developed before the IEEE 802.3az Energy-Efficient Ethernet standard was finalized.

Potential savings

In 2005, all the

network interface controller A network interface controller (NIC, also known as a network interface card, network adapter, LAN adapter or physical network interface, and by similar terms) is a computer hardware component that connects a computer to a computer network. Ear ...

s in the United States (in computers, switches, and routers) used an estimated 5.3 terawatt-hours of electricity. According to a researcher at the

Lawrence Berkeley Laboratory Lawrence Berkeley National Laboratory (LBNL), commonly referred to as the Berkeley Lab, is a United States national laboratory that is owned by, and conducts scientific research on behalf of, the United States Department of Energy. Located in ...

, Energy-Efficient Ethernet can potentially save an estimated a year in energy costs in the U.S. Most of the savings would come from homes () and offices (), and the remaining from data centers.

Concepts

The power reduction is accomplished in a few ways. In

Fast Ethernet In computer networking, Fast Ethernet physical layers carry traffic at the nominal rate of 100 Mbit/s. The prior Ethernet speed was 10 Mbit/s. Of the Fast Ethernet physical layers, 100BASE-TX is by far the most common. Fast Ethern ...

and faster links, constant and significant energy is used by the

physical layer In the seven-layer OSI model of computer networking, the physical layer or layer 1 is the first and lowest layer; The layer most closely associated with the physical connection between devices. This layer may be implemented by a PHY chip. The ...

as transmitters are active regardless of whether data is being sent. If they could be put into sleep mode when no data is being sent, that energy could be saved. When the controlling software or firmware decides that no data needs to be sent, it can issue a low-power idle (LPI) request to the Ethernet controller physical layer

PHY PHY is an abbreviation for the physical layer of the OSI model and refers to the circuitry required to implement physical layer functions. PHY or Phy may also refer to: * Phy, the drug methadone * Phetchabun Airport (IATA code), Thailand See ...

. The PHY will then send LPI symbols for a specified time onto the link, and then disable its transmitter. Refresh signals are sent periodically to maintain link signaling integrity. When there is data to transmit, a normal IDLE signal is sent for a predetermined period of time. The data link is considered to be always operational, as the receive signal circuit remains active even when the transmit path is in sleep mode.

Green Ethernet

Green Ethernet technology was a superset of the 802.3az standard. In addition to the link load power savings of Energy-Efficient Ethernet, Green Ethernet works in one of two ways. First, it detects link status, allowing each port on the switch to power down into a standby mode when a connected device, such as a computer, is not active. Second, it detects cable length and adjusts the power used for transmission accordingly. Standard switches provide enough power to send a signal up to . However, this is often unnecessary in the SOHO environment, where of cabling are typical between rooms. Moreover, small data centers can also benefit from this approach since the majority of cabling is confined to a single room with a few meters of cabling among servers and switches. In addition to the pure power saving benefits of Green Ethernet, backing off the transmit power on shorter cable runs reduces alien crosstalk, and improves the overall performance of the cabling system. Green Ethernet also encompasses the use of more efficient circuitry in Ethernet chips, and the use of offload engines on Ethernet interface cards intended for network servers. In April 2008, the term was used for switches, and, in July 2008, used with wireless routers which featured user-selectable off periods for

Wi-Fi Wi-Fi () is a family of wireless network protocols, based on the IEEE 802.11 family of standards, which are commonly used for local area networking of devices and Internet access, allowing nearby digital devices to exchange data by radio wave ...

to further reduce energy consumption. Green Ethernet was first employed on home products. However, low port counts mean that significant energy savings are not going to be made using this technology only in the home. Turning off existing devices when they are idle is likely to provide a more immediate saving. Projected power savings of up to 80 percent were estimated using Green Ethernet switches, translating into a longer product life due to reduced heat dissipation.

References

External links

IEEE P802.3az Energy Efficient Ethernet Task Force
* Blog for Energy-Efficient Ethernet techniques and news analyses, circa 2009. {{Ethernet IEEE 802 Ethernet Energy conservation Computers and the environment

Potential savings

Concepts

Green Ethernet

See also

References

External links