The first green Ethernet standard is not expected until 2012; the IEEE 802.3. For now, however, D-Link has a global first: its green Ethernet technology, as seen in products like this 5-port Gigabit Desktop Switch, aimed at SMBs. Such a switch saves up to 44% of idle-time power (when the computers are off; the switches and routers are always left on). It even saves up to 27% power when in operation. (These are company-supplied figures.) So for an initial price premium of about 15-20% (expected to come down after production volume ramps up), D-Link says you can save 30 to 40% of the power your switches consume. Planned together with lower power devices (such as LCDs instead of TFTs) that can also help cut down your capex cost of UPS backup capacity. (And all that also cuts down heat, and thus air-con capacity-saving you on generator capacity.)

How does such a 'Green Ethernet' product work? It senses if the PC connected to a given port is on or off, by pinging it, and if it finds the PC is off, it drops that port to a low-power standby mode. And from the ping response, it also auto-senses the length of the cable to the PC, and automatically drops the power level if the distance is less. Normal switches keep all ports at maximum power, to allow variable cable lengths up to 20 meters. Does all ths on-the-fly power efficiency affect performance? Dataquest asked CyberMedia Labs to test the 5-port gigabit desktop switch from D-Link's Green Ethernet series: this is targeted at SMBs. This ultracompact switch required no set up at all: it was plug'n' play all the way, supporting 10, 100 or 1,000 Mbps networks, and can run in half and full duplex mode.

A 'cable diagnostic' feature checks if the cable connected is good, saving on troubleshooting time:..an amber light shows a cable fault on the corresponding port's LED. Our lab test found network performance very good (TCP throughput at 727 Mbps, UDP at 255Mbps, and 1 ms response, on the Ucheck benchmark with two PCs connected),which are really good scores. 1 GB of data went through in 189 sec, which is fast. So it's green, quick, and costs just a bit more than a normal gigabit switch. Good going.

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