The IEEE's Energy Efficient Ethernet Task Force is nearing a Draft 1.0 specification, getting closer to making network communications a bit greener.

The IEEE 802.3az Task Force, formed last year, is reviewing the Draft 0.9 specification and this week will start to consider all comments on the spec as it creates Draft 1.0.

The group decided to concentrate on copper-based Ethernet connections, though it had once flirted with the idea of making fiber-optic links more energy-efficient, too. The group has indicated that this question may be taken up again later. The group is also looking at making backplane Ethernet more energy-efficient.

The main mechanism for saving power is something called Low Power Idle, or LPI, which can be used for 100Base-TX, 1000Base-T and 10GBase-T. In this technique, power is turned off when circuits are not being used. The group has decided that it will use auto-negotiation - when the devices at the two ends of a link are communicating the speeds they are capable of to one another - to let the devices inform one another whether they support Energy Efficient Ethernet.

The group will use Link Layer Discovery Protocol (LLDP) to communicate changes in control policy - for example, users may choose energy savings over performance, or vice versa, according to a presentation on the 802.3az Web site. This will require an extension to the LLDP MIB, as well as a MIB, or management information base, for Energy Efficient Ethernet itself.

One downside acknowledged by the task force is that Energy Efficient Ethernet would add latency. When a physical interface is in low power mode, it has to be woken up. The time for the interface to wake up could vary, but it's something to consider.

It has been suggested that making Ethernet equipment more energy-efficient could be a competitive edge.

Jeff Caruso is site editor at Network World.