User manual

APS User Manual
58
1.2.1-7 EEE
EEE is a power saving option that reduces the power usage when there is very low traffic utilization
(or no traffic).
EEE works by powering down circuits when there is no traffic. When a port has data to be
transmitted all circuits are powered up. The time it takes to power up the circuits is called the
wakeup time. The default wakeup time is 17 µs for 1Gbit links and 30 µs 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 devices have all circuits powered up when traffic is transmitted. Each device can
exchange information about the devices individual wakeup time using the LLDP protocol.
For maximizing the power saving, the circuit isn't started as soon as data is ready for a port, but is
instead queued until 3000 bytes of data is ready to be transmitted. To eliminate large delay’s in
cases where the data is less than 3000 bytes, data will always be transmitted after 48 µs, giving a
maximum latency of 48 µs + the wakeup time.
If desired it is possible to minimize the latency for specific frames, by mapping the frames to a
specific queue (done with QOS), and then mark the queue as an urgent queue. When an urgent
queue gets data to be transmitted, the circuits will be powered up at once and the latency will be
reduced to the wakeup time only.
Web Interface
To configure the EEE Power Saving options via the Web Interface:
1. Click Configuration, Port and EEE.
2. To enable the EEE function for a port tick the box next to the corresponding port.
3. Select the desired EEE Urgent Queue values for each port.
4. Click the Apply button to save your changes or the Reset button to revert to previous
settings.