Linksys LGS308 User Manual page 57

Power savings, current power consumption and cumulative energy saved can be monitored. The
total amount of saved energy can be viewed as a percentage of the power that would have been
consumed by the physical interfaces had they not been running in Green Ethernet mode.
The saved energy displayed is only related to Green Ethernet. The amount of energy saved by
EEE is not displayed.
Energy Efficient Ethernet
EEE is designed to save power when there is no traffic on the link. In Green Ethernet, power is
reduced when the port is down. With EEE, power is reduced when the port is up, but there is no
traffic on it.
When using 802.3 EEE, systems on both sides of the link can disable portions of their
functionality and save power during periods of no traffic. 802.3 EEE supports IEEE 802.3 MAC
operation at 100 Mbps and 1000 Mbps.
LLDP is used to select the optimal set of parameters for both devices. If LLDP is not supported by
the link partner, or is disabled, 802.3 EEE will still be operational, but it might not be in the optimal
operational mode.
The 802.3 EEE feature is implemented using a port mode called Low Power Idle (LPI) mode. When
there is no traffic and this feature is enabled on the port, the port is placed in the LPI mode, which
reduces power consumption dramatically.
Both sides of a connection (device port and connecting device) must support 802.3 EEE for it to
work. When traffic is absent, both sides send signals indicating that power is about to be reduced.
When signals f s (and not in Down status), and power is reduced.
For ports to stay in LPI mode, the Keep Alive signal must be received continuously from both
sides.
Power Saving by Disabling Port LEDs
Use the Green Ethernet feature to disable port LEDs (link, speed, and PoE) when they are not
needed. Enable them if needed (debugging, connecting additional devices, etc.).
Advertise Capabilities Negotiation
802.3 EEE support is advertised during the Auto-Negotiation stage. Auto-Negotiation provides a
linked device with the capability to detect the abilities (modes of operation) supported by the
device at the other end of the link, determine common abilities, and configure itself for joint
operation. Auto-Negotiation is performed at the time of link-up, on command from management,
or upon detection of a link error. During the link establishment process, both link partners
exchange their 802.3 EEE capabilities. Auto- Negotiation functions automatically without user
interaction when it is enabled on the device.
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