Application Guide

[17]
Software User's
Manual
–
Version 3.0
Configuration > Green Ethernet > Port Power Savings
Port Power Saving Configuration
What is EEE
EEE is a power saving option that reduces the power usage when there is low or no traffic utilization.
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 named Wakeup
Time. The default wakeup time is 17 ms for 1Gbit links and 30 ms 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 have all circuits powered up when traffic is transmitted. The devices can exchange
wakeup time information using the LLDP 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 such ports.
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 is 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.
Optimize EEE for
The switch can be set to optimize EEE for either best power saving or least traffic latency.
Setting Description
Factory
Default
Power Best power saving
Latency
Latency Least traffic latency