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## Mission-Tags

~~TAGCLOUD:50~~

Labeling things with the term “green” has become quite popular these days. While evaluating unmanaged SOHO Gigabit-Ethernet switches for Apollo's core net-infrastructure, a lot of “green” switches turned up. After sifting through numerous datasheets D-Link's DGS-1008D seemed to be the top choice when power consumption is an issue.

The DGS-1008D employs intelligent power saving modes to actively reduce energy consumption. Unconnected ports or ports without a client in powered or standby mode are put to sleep. The switch also determines, whether the ethernet cable is longer than 20m, if it's not, the port reduces its transmit output power to save even more energy.

## Power Consumption Analysis

Fortunately muCCC had the 2nd generation of these switches deployed, so it was possible to take comparative measurements with different use-scenarios and two generations of the same model in a controlled environment. The switches were measured directly on the 5V input in order to avoid misleading results due to power conversion losses. Each switch was tested in the same environment using different operation modes to determine a more real-life power consumption profile:

 DGS-1008D G2 DGS-1008D G3 Connected Mode Current Power Current Power 0 Clients Switch only 66-93mA 0.33-0.46W 67-111mA 0.33-0.55W 1 Client Client Stdby 100-160mA 0.5-0.8W 109-124mA 0.54-0.62W 2 Clients Client Stdby 141-194mA 0.70-0.97W 153-161mA 0.76-0.80W 2 Clients Client Idle 160-200mA 0.8-1W 170mA 0.85W 3 Clients Client SCP 250mA 1.25W 210-220mA 1.07W 4 Clients Client SCP 250mA 1.25W 210-220mA 1.07W

## Reliability & Performance

The DGS-1008D test candidate has been up and running 24×7 for more than 365 days now without any glitch or the necessity to power cycle. Power saving often leads to compromises in performance but the switch performed equally well compared to a CISCO 3560, that was in use before power consumption became a major issue.

## Conclusion

Grid powered devices still have the luxury to be able to consume more power than absolutely necessary, since the limiting factor is money and not power itself. Off-Grid scenarios change that point of view on costs, as the value is no longer money, but the painfully finite element of power itself.

There are still a lot of devices out there with a standby-consumption of well above 10W, the DGS-1008D G3 connects 4 clients, actively transfers a lot of data and consumes about 1W. D-link obviously did a good job with this, although there is a little curiosity in StandBy: The G2 consumes a little less power in StandBy, when no clients are connected but the G3 saves considerably more power when active so overall the G3 is a very good evolutionary step in low-power consumption Gigabit-Ethernet technology.

The only drawback of these switches is their un-managed nature. Hopefully, in the future even managed switches can operate with this kind of power consumption profile.

Other manufacturers, who also build similar products, may always send us their products for hardcore real live evaluation as well :)

## Discussion

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