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Chapter 3 Configuration and Operation
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3.3.3 Power Reduction (Green Ethernet)
The configuration under the "Power Reduction" menu includes two power saving techniques.
3.3.3.1 Green Ethernet LED
Configure the LED light intensity to reduce power consumption.
The LED light intensity may be adjusted in a percentage of intensity during programmable time periods. In the
above setting example, the LED intensity has been adjusted to 50% during daylight hours and reduced to only 10%
intensity during night hours.
The maintenance checkbox will bring LED intensity to 100% for 10 seconds in the event of any error (such as link
down).
3.3.3.2 Green Ethernet Configuration
Configure EEE (Energy-Efficient Ethernet) Ethernet power savings.
Port Power Savings Configuration
Enables/disables the EEE function for this switch. The two options are:
* [checked] - The EEE function is enabled. This is the default setting.
* [not checked] - EEE is not enabled.
EEE (Energy-Efficient Ethernet)
EEE is a power saving option that reduces the power usage when there is low or no traffic utilization. EEE was
developed through the IEEE802.3az task force of the Institute of Electrical and Electronic Engineers (IEEE).
EEE works by powering down circuits when there is no traffic. When a port gets data to be transmitted all circuits
are powered up. The time it takes to power up the circuits is called wakeup time. The default wakeup time is 17 us for
1Gbit links and 30 us for other link speeds. EEE devices must agree upon the value of the wakeup time in order to
make sure that both the receiving and transmitting device has all circuits powered up when traffic is transmitted. The
devices can exchange wakeup time information using the LLDP (Link Layer Discovery Protocol) protocol.
EEE works for ports in auto-negotiation mode, where the port is negotiated to either 1G or 100 Mbit full duplex
mode.
For ports that are not EEE-capable the corresponding EEE checkboxes are grayed out and thus impossible to enable
EEE for.
When a port is powered down for saving power, outgoing traffic is stored in a buffer until the port is powered up
again. Because there are some overhead in turning the port down and up, more power can be saved if the traffic can
be buffered up until a large burst of traffic can be transmitted. Buffering traffic will give some latency in the traffic. For
traffic that should not be held back, urgent queues may be assigned to reduce latency yet still result in overall power
saving.